Review of the Status and Management of Double-crested ...bays or inlets to enhance foraging success (Glanville 1992). The diet of cormorants has been studied extensively in North America

Review of the Status and Management of Double-crested Cormorants in Ontario

2006

Ministry of Natural Resources

Fish and Wildlife Branch Wildlife Section

http://www.mnr.gov.on.ca/MNR/index.html

Review of the Status and Management of Double-crested Cormorants in Ontario 2006 ________________________________________________________________________

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Ministry of Natural Resources 1 Wildlife Section

CONTRIBUTING AUTHORS Jamie Stewart, Wildlife Biologist, Ministry of Natural Resources (Editor) Patrick Hubert, Senior Avian Biologist, Ministry of Natural Resources Chip Weseloh, Wildlife Biologist, Canadian Wildlife Service Tim Bellhouse, Senior Monitoring Ecologist, Ministry of Natural Resources Mark Ridgway, Research Scientist, Ministry of Natural Resources Jennifer Backler, Economist, Ministry of Natural Resources Brian Huis, Parks Planning Specialist, Ministry of Natural Resources John Almond, Area Supervisor, Ministry of Natural Resources Doug Campbell, Pathologist, Canadian Cooperative Wildlife Health Centre Brad Steinberg, Algonquin Park Biologist, Ministry of Natural Resources Gary Brown, Legislation Specialist, Ministry of Natural Resources Karen Laws, Wildlife Policy and Program Specialist, Ministry of Natural Resources © Queen’s Printer for Ontario, 2006 MNR 52010 ISBN 1-4249-0936-8 Cover Photo Credit: Doug Guay ACKNOWLEDGEMENTS We wish to acknowledge the assistance of Patricia Edwards (OMNR), Eva Kennedy (OMNR), Andrew Jobes (OMNR), Ralph Toninger (TRCA), and Shauna Hanisch (USFWS) for reviewing selected sections of this document. Deb Stetson (OMNR), Mike Bohm (OMNR) and Freya Long (OMNR) assisted with organizational direction and publication of this document. Many thanks to Tania Havelka (CWS), Tommy King (APHIS-USDA), Jim Farquhar (NYSDEC), Don Tyerman (OMNR), Kevin Esseltine (OMNR), and Mike Gatt (OMNR) for providing assistance in the collection of information. Special thanks to all OMNR staff, and other provincial and U.S. wildlife agency staff (too many to name) who completed cormorant surveys for this report. Thanks to the official sponsors of the Ontario Breeding Bird Atlas (Bird Studies Canada, Canadian Wildlife Service, Federation of Ontario Naturalists, Ontario Field Ornithologists, and Ontario Ministry of Natural Resources) for supplying Atlas data, and to the thousands of volunteer participants who gathered data for during the Breeding Bird project. RECOMMENDED CITATION Ontario Ministry of Natural Resources. 2006. Review of the status and management of double-crested cormorants in Ontario. Fish and Wildlife Branch. Wildlife Section. Peterborough, Ontario. 76 p.

Cette publication hautement specialisée Review of the Status and Management of Double-crested Cormorants in Ontario 2006 n’est disponible qu’en Anglais en vertu du Règlement 411/97 qui en exempte l’application de la Loi sur les services en français. Pour obtenir de l’aide en français, veuillez communiquer avec Linda Maguire au ministère des Richesses naturelles au [email protected]


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TABLE OF CONTENTS 1.0 Synopsis…...………………………………………………………………… 3 2.0 Biology………………………………………………………………………. 4 3.0 History………………………………………………………….…………… 6 4.0 Population Status…………………………………………………………… 8 4.1 Great Lakes………………………………………………………....... 9 4.1.1 Lake Superior……………………………………………….. 11 4.1.2 Lake Huron (Georgian Bay)………………………………... 13 4.1.3 Lake Erie………………………….……………………….... 15 4.1.4 Lake Ontario………………………………………………... 17

4.1.5 St. Lawrence River…………………………………………. 19 4.2 Inland Lakes………………………………………………………... 21

4.2.1 Northwest Region…………………………………………... 22 4.2.2 Northeast Region………………….………………………... 23 4.2.3 Southern Region………………….………………………… 24 5.0 Concerns about Cormorants in Ontario………………………………… 26

5.1 Impacts on Fish…………………………………………………….. 26 5.2 Impacts on Vegetation……………………………………………… 30 5.3 Impacts on other Species…………………………………………… 32 5.4 Impacts on Humans………………………………………………… 34

6.0 Research and Monitoring………………………………………………… 36

6.1 Lake Huron Monitoring and Research Program……….…………… 36 6.2 East Sister Island Provincial Nature Reserve……………….………. 37 6.3 Tommy Thompson Park Monitoring……………………………….. 39 6.4 Presqu’ile Provincial Park Cormorant Management Strategy……… 41 6.5 Disease Monitoring ………………………………………………… 44 6.6 Great Lakes Monitoring…………………………………………….. 44 6.7 Inland Lake Monitoring…………………………………………….. 45 6.8 Algonquin Provincial Park Monitoring…………………………….. 46

7.0 Ontario Legislation and Current Provincial Policy…………………….. 48 7.1 MNR Role & Responsibilities……………………………………… 48 7.2 Crown Land………………………………………………………… 49 7.3 Private Land………………………………………………………… 49 8.0 Cormorant Management in Other Jurisdictions……….……………….. 50 8.1 Canadian Provinces…………………………….…………………… 50

8.2 United States of America…………………………………………… 52 9.0 Research and Information Needs………………………………………… 55 10.0 References…………………………………………………………………. 60


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1.0 SYNOPSIS Ontario’s double-crested cormorant (Phalocrocorax auritus, henceforth cormorant) population has increased dramatically over the past 30 years. This rapid population growth and range expansion has resulted in public concerns regarding impacts to the environment, and conflicts with humans. Cormorant management has become a contentious issue among stakeholder groups, landowners, and interested citizens. In 1997, the Ontario Ministry of Natural Resources (OMNR) completed a “Review of the Population Status and Management of Double-crested Cormorants in Ontario” in response to increasing cormorant populations, and public demand for information and management options (OMNR 1997). The review document was posted on the Environmental Bill of Rights in May and June of 1997. In 1998, the finalized review document established the guiding policy for the management of cormorants in Ontario (OMNR 1997). Since 1997, the scientific community, and provincial and federal agencies have increased the knowledge base with respect to cormorant biology, population dynamics, environmental impacts, and future management challenges. This document reports on this new knowledge, and expands on the information presented in the 1997 review document. It presents information on biology, history, current population status, environmental impacts, and research/monitoring of cormorants in Ontario. Relevant cormorant legislation, provincial policy, and management activities in other Canadian and United States jurisdictions has also been summarized. The purpose of this review document is to summarize available information on the status, biology and management of cormorants in Ontario. It provides a basis for the future development of management options. Information included in this document was assembled from a review of scientific literature, discussions with cormorant experts, and MNR field offices, provincial, federal and U.S. wildlife management agencies. It is not intended to be an exhaustive account of the topics. For specific details the reader should review the referenced literature. The OMNR is committed to maintaining a diversity of environments in Ontario, including habitat for cormorants. The future management of cormorants in Ontario will consider relevant science and consultation with the public.


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2.0 BIOLOGY The double-crested cormorant (Phalocrocorax auritus) is a relatively large, diurnal, fish-eating, migratory waterbird that is native to Canada. The genus name, Phalacrocorax, is Greek for “bald-headed raven”; the species name, auritus, is Latin for “eared” and refers to feather crests above the eyes which are only fully developed early in the breeding season (Hatch and Weseloh 1999). Identification The double-crested cormorant is the only cormorant species found in the Great Lakes region (Cadman et al. 1987, OMNR 2005a, Sandilands 2005). It is a medium to large (typical length 70 – 90 cm, body mass 1.2 – 2.5 kg) greenish-black coloured waterbird (Hatch and Weseloh 1999). The bill is long (5-8 cm), slender and hooked at the end. The bird has brilliant turquoise eyes, a golden throat patch, and a cobalt-blue mouth for a short time prior to and during the breeding season. Range In Canada, cormorants breed as far west as British Columbia and easterly to the Atlantic Coast including Newfoundland (Godfrey 1986, Hatch and Weseloh 1999). In Ontario, they are found throughout the Great Lakes and have a breeding range that extends north to southern James Bay (Cadman et al. 1987, OMNR 2005a, Sandilands 2005). Populations nesting in Ontario or on the Great Lakes migrate south along the Mississippi River drainage or travel east to the Atlantic coast and then south to the Gulf coast (Palmer 1962, Cadman et al. 1987, del Hoyo et al. 1992). Southward migration typically begins as early as the end of August and extends through October; most birds return to the Great Lakes the following April (Weseloh and Collier 1995, Hatch and Weseloh 1999). The winter range of cormorants migrating from the Great Lakes typically extends from New Jersey and Pennsylvania on the Atlantic Coast southward and inland, from southern Illinois, Tennessee and Arkansas south to the Gulf of Mexico along major rivers to south-eastern Pennsylvania, central Maryland, and throughout the lower coastal plains of Virginia and the Carolinas (Hatch and Weseloh 1999). This area includes the lower Mississippi River where the catfish farming industry has greatly developed in the last 30 years (Brunson 1991, Stickley et al. 1992, Wywialowski, 1999). Nesting and Reproduction Cormorants are colonial nesting birds, which require sites that are safe from ground predators and close to feeding areas (usually < 10km) (Wires et al. 2001). On the Great Lakes, cormorants typically select islands or peninsulas to establish nesting sites. Nests are found on the ground or within the canopy of woody vegetation, directly adjacent to water where a food supply is easily accessible (Hatch and Weseloh 1999). Nests are composed of sticks, leaves, weed stalks and other available material (Johnsgard 1993,


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Sandilands 2005). Both male and female birds share in nest-building, incubation and feeding of the chicks. While the timing of nesting can vary considerably on the Great Lakes, egg laying on the lower lakes normally starts in late April – early May after the birds have gone through courtship and nest building. It is not uncommon to have egg laying as late as August in Ontario (Peck and James 1983). Cormorants lay an average of three to four pale greenish-blue eggs which may be partially covered with a white chalky layer (Johnsgard 1993, Hatch and Weseloh 1999, OMNR 2005a, Sandilands 2005). The birds have an unusual habit of incubating their eggs by wrapping the webs of their feet around them (Johnsgard 1993, Hatch and Weseloh 1999). The eggs hatch after 25-28 days of incubation. The young are fully independent about 10 weeks after hatch (i.e., usually beginning in mid-July). Cormorants typically become sexually mature by 3 years of age and there is evidence to suggest that these young cormorants will attempt to breed at or in close proximity to their natal colony (Wires et al. 2001). In all seasons, cormorants require a suitable place for night time roosting and daytime resting or loafing. Roosts and resting places are often on exposed sites such as rocks, sandbars, pilings or trees near preferred fishing sites (Stenzel et al. 1995, Weseloh and Collier 1995). Diet and Foraging Cormorants are fish-eating birds that typically feed on slow-moving or schooling fish that are up to approximately 15cm in length (Craven and Lev 1987, Weseloh and Ewins 1994, Neuman et al. 1997, Hatch and Weseloh 1999). They are an opportunistic, generalist feeder, normally preying on abundant and easy to catch fish species (Ludwig et al. 1989, Hatch and Weseloh 1999). Cormorants are known to be opportunistic to the extent they will congregate at specific times and areas where fish concentrations are high, such as spawning grounds, stocking release sites, and aquaculture facilities; however they are also known to feed solitarily. Cormorants typically forage during the day in shallow water (< 8 – 10m) within 5 km of the shore (Wires et al. 2001). Cormorants have been observed to forage in cooperative flocks in order to force schools of fish into shallow bays or inlets to enhance foraging success (Glanville 1992). The diet of cormorants has been studied extensively in North America (Roney 1979, Hobson et al. 1989, Ross and Johnson 1995, Neuman et al. 1997, Glahn et al. 1998, Rail and Chapdelaine 1998, Bur et al. 1999, Trapp et al. 1999, Johnson et al. 2002, Wires et al. 2001). Research suggests that the majority of their diet is composed of small fish that are of relatively low economic and commercial value. In the Great Lakes region these species primarily include: alewife (Alosa pseudoharengus), rainbow smelt (Osmerus mordax), gizzard shad (Dorsoma cepadianum), Cyprinid species, and to a lesser extent, sticklebacks (Gasterosteidae sp.), white suckers (Catostomus commersoni), pumpkinseeds (Lepomis gibossus), rock bass (Ambloplites rupestris), and more recently,


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round goby (Neogobius melanostomus) (Ludwig et al. 1989, Weseloh and Collier 1995, Bur et al. 1999, Johnson et al. 1999, Trapp et al. 1999, Wires et al. 2001, Johnson et al. 2002, Ratcliff 2004, Somers and Quinn unpublished data). However, in some cases cormorants have been known to feed heavily on yellow perch (Perca flavens), a commercially and recreationally important species and on smaller numbers of smallmouth bass (Micropterus dolmieui) and walleye (Stizostedion vitreum) (Burnett et al. 2002, Lantry et al. 2002, Johnson et al. 2004, Rudstam et al. 2004). Occasionally, cormorants will consume small invertebrates such as crayfish and aquatic insects (Palmer 1962, Johnson et al. 1997). Survival and Mortality Cormorants have a mean adult life expectancy of approximately 6 years, although they have been known to live to approximately 18 years in the wild (Van der Veen 1973, Klimkiewicz and Futcher 1989, Johnsgard 1993). Young birds and eggs exhibit the highest mortality rate due to nesting disturbances at breeding colonies where hatchlings and eggs are often exposed to predation by several species of gulls (Larus sp.) (Hatch and Weseloh 1999). Young cormorants are also taken by coyotes, foxes, and raccoons when colonies are accessible by land (Hatch and Weseloh 1999). Egg mortality was extremely high and recruitment was virtually zero during the 1960s and early 1970s due to elevated contaminant levels in the Great Lakes (Weseloh et al. 1983, Price and Weseloh 1986). Predation by bald eagles (Haliaeetus leucocephalus), entanglement in fishing gear, culling and harassment, Newcastle disease, and avian botulism are all known to contribute to mortality in cormorants (Hatch and Weseloh 1999, Wires et al. 2001). 3.0 HISTORY Double-crested cormorants were known to be present in north-western Ontario on Lake of the Woods as early as the 1790s (Peck and James 1983, Tanner 1994, Korfanty et al. 1999). Cormorant populations expanded across the Great Lakes between the 1900s and the 1950s; although it is unclear whether this was the result of natural range expansion or re-colonization (Weseloh et al. 1995, Wires et al. 2001, Wires and Cuthbert 2006). Nevertheless, cormorant colonization was documented moving eastward across Ontario from the early 1900s to the late 1930s (Fargo and Van Tyne 1927, Baillie 1947, Core 1948, Postupalsky 1978, Peck and James 1983, Cadman et al. 1987, del Hoyo et al. 1992, Weseloh et al. 1995). Recent research by Wires and Cuthbert (2006) suggests that cormorants may have nested in small numbers throughout the Great Lakes prior to 1900; however few formal/confirmed records were documented at this time. Cormorant numbers continued to grow throughout the Great Lakes into the 1940s and 1950s. Concerns for recreational and commercial fisheries prompted Ontario to implement a cormorant control program in the late 1950s in specific areas of the Great


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Lakes (primarily on Georgian Bay) (Omand 1947, Postupalsky 1978, Weseloh and Collier 1995). Early control measures included the destruction of eggs and nests to which the birds responded by laying more eggs at new nesting sites. Further control methods included spraying the eggs with a solution of formaldehyde and soap to cut off respiration through the eggshell and suffocate the embryo. This control method left the egg intact and the cormorants continued to incubate the dead eggs rather than re-nest (Weseloh and Collier 1995, Korfanty et al. 1999). These early control attempts only slowed the growth of the population during the 1950s and did not significantly reduce the Great Lakes population. A cormorant control program remained in effect in Ontario until 1966 (Weseloh and Collier 1995). Despite their range expansion and prolific nature, cormorant populations experienced a dramatic decline throughout the 1960s and early 1970s. The Great Lakes-wide population dwindled to approximately 130 nesting pairs by the early 1970s and breeding birds had completely disappeared from the U.S. portion of the Great Lakes (Anderson and Hamerstrom 1967, Postupalsky 1978, Weseloh et al. 1995). In the late 1960s, biologists discovered that this drastic population decline was the result of reduced recruitment due to eggshell thinning and reproductive failure caused by high levels of toxic contaminants in the Great Lakes (i.e., DDE, PCB, etc.) (Keith 1966, Ludwig and Tomoff 1966, Weseloh et al. 1983). Thin eggshells could not withstand the weight of adult cormorants during incubation and would break before reaching term, killing the embryo (Postupalsky 1978, Weseloh et al. 1983). Cormorant numbers declined dramatically because the lower production rate could not offset the mortality rate in adults (Weseloh et al. 1983). As a result, some U.S. states (i.e., Wisconsin, Illinois, Michigan) listed cormorants under their endangered species legislation in the 1970s and early 1980s (Weseloh et al. 1995). New regulations, enhanced enforcement and public awareness surrounding toxic contaminants resulted in significantly reduced levels of toxic chemicals (i.e., reduced by 80%) in the Great Lakes between 1971 and 1989 (Weseloh and Ewins 1994, Weseloh and Collier 1995, Weseloh and Pekarik 1999). As a result, reproductive success returned to relatively normal levels for cormorants and their populations began a radical recovery in the mid – late 1970s. From 1973 to 1993, cormorant numbers increased by nearly 300-fold to 38,000 nesting pairs and 80 new colonies across the Great Lakes (Cadman et al. 1987, Weseloh and Collier 1995, Weseloh et al. 1995). The rapid increase in cormorant numbers led to the removal of U.S. state (i.e., Wisconsin, Illinois, Michigan) protection under endangered species legislation in the Great Lakes region during the late 1980s and early 1990s (Weseloh et al. 1995). The dramatic recovery of cormorant populations cannot be solely attributed to decreased contamination in the Great Lakes. Population increases have been much higher than the rate of increase during the initial range expansion into the lower Great Lakes during the 1930s and 1940s. A rich and abundant food supply in breeding and wintering areas also played a significant role in their dramatic recovery (Christie 1974, Christie et al. 1987, Glahn and Stickley 1995, Weseloh and Collier 1995, Glahn et al. 1996, Hatch and Weseloh 1999, Wires et al. 2001). Alewife and rainbow smelt were the primary food


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sources for cormorants in the Great Lakes and these prey fish stocks experienced significant population increases in response to the decline in large predatory fish during this time (Christie 1974, Hartmann 1988, Weseloh and Collier 1995). Increased aquaculture and abundant food supply at cormorant wintering grounds (i.e., the southern United States) likely contributed to an increase in over-winter survival of cormorants as well (Glahn et al. 1995, Glahn et al. 1999). Throughout the 1990s cormorant populations continued to increase across the Great Lakes and expand into previously unoccupied areas including some inland lakes. The highest recorded cormorant populations in the history of the Great Lakes were recorded during the late 1990s and early 2000s (Weseloh et al. 1995, 2002, Wires and Cuthbert 2006). Over the past five years some regions of the Great Lakes have begun to show signs that cormorant populations are levelling off. Some areas of the Great Lakes basin have experienced significant decreases in cormorant numbers over the past five years, which may suggest that a new biological carrying capacity is being reached (OMNR unpublished data, 2005, Weseloh et al. 2006). 4.0 POPULATION STATUS This section of the report presents a summary of all available double-crested cormorant population information for the Canadian Great Lakes (i.e., Lake Superior, Lake Huron, Lake Erie, and Lake Ontario) and the upper St. Lawrence River. The purposes of this section are:

1) To present the current population status for cormorants on the Canadian Great Lakes and the upper St. Lawrence River.

2) To present the population trends on the Canadian Great Lakes and the upper St.

Lawrence River over the last 8 years (i.e., since the 1997 OMNR status report).

3) To contrast the size of the cormorant populations in the four Canadian Great Lakes and the upper St. Lawrence River.

The Canadian Wildlife Service and the U.S. Fish and Wildlife Service coordinate a Great Lakes-wide survey of all colonial birds, including cormorants, about every 10 years. The last colonial bird survey was conducted from 1997 – 1999. In 2005, Canadian and U.S. wildlife officials agreed to conduct a Great Lakes-wide cormorant count to update the existing population census for the bird. A cormorant population census is also conducted annually in the lower Great Lakes (including Lake Huron in most years) through the cooperation of Ontario, Canadian federal agencies, and U.S. state agencies. This section of the report presents the cormorant population census and temporal trends across each of the Canadian (Ontario) Great Lakes, which is based on both annual and decadal cormorant nest counts coordinated by the Canadian Wildlife Service and the Ontario Ministry of Natural Resources (described in more detail in section 6.6 Great


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Lakes Monitoring) and from unpublished studies by Weseloh et al. (2006, in press) and Weseloh and Shutt (2005). The reader should note that cormorant nest count data for Lake Superior and Lake Huron only include Ontario colonies because consecutive historic U.S. nest counts for these lakes are not available. Nest count data for Lake Erie, Lake Ontario, and the upper St. Lawrence River include both Canadian and U.S. data. 4.1 GREAT LAKES The Great Lakes population of cormorants has increased dramatically over the last 30 years. These changes have been documented by several authors: Weseloh et al. 1983, 1995, 2000, 2002, 2006, in press, Postupalsky 1978, Ludwig 1984, Hatch 1995, Blokpoel and Tessier 1996, Weseloh 1996, Tyson et al. 1999, Cuthbert et al. 2001, Wires et al. 2001, Havelka and Weseloh in press. This drastic population increase is likely due to a combination of factors, including reduced human persecution, declining levels of organochlorine contaminants, and an abundance of forage-base fish (Christie 1974, Weseloh et al. 1995, Ryckman et al. 1998). Table 4.1 shows a brief summary of the increasing Great Lakes region cormorant breeding population.

Table 4.1 Approximate number of cormorant nests (= number of cormorant pairs) counted or estimated for the Great Lakes region, 1950 – 2005. * indicates Great Lakes nest count minus Lake Michigan and U.S. portions of Lake Huron and Lake Superior.

Year Approximate Number of Nests Source

1950 900 Postupalsky 1978

1962 300 Ludwig 1984

1972 135 Postupalsky 1978 Weseloh et al. 1995

1983 2,400 Weseloh et al. 1995*

1991 38,000 Weseloh et al. 1995

1997 89,000 Cuthbert et al. 2001 Weseloh et al. 2006

2000 115,000 Weseloh et al. 2002

2005 113,000 Weseloh et al. 2006

Since the early 1990s, the total number of cormorant nests (i.e., breeding pairs) on the Ontario side of the Great Lakes has more than doubled (Weseloh et al. 1995, 2006). Ontario reported approximately 175 nesting colonies and more than 59,000 nests in 2005 (Weseloh et al. 2006).


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Lake Huron (including Georgian Bay) and Lake Ontario have the largest nesting populations of cormorants in the Canadian Great Lakes (Figure 4.1) (Weseloh et al. 2006). In the past, fish abundance and favourable nesting habitat (i.e., uninhabited islands and peninsulas) have driven population increases on Lake Huron and Lake Ontario; however in recent years there have been indications that these populations are stabilizing (Figure 4.1). Declines in available food supply may be partly responsible in reducing the cormorant carrying capacity on Lake Huron. Ontario and U.S. population control activities may be partly responsible for population declines on Lake Ontario.

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Figure 4.1 Great Lakes-wide cormorant nest counts for Lake Ontario (blue), Lake Erie (green), and the upper St. Lawrence River (orange) (counts include Canada and U.S. colonies); and Canada only nest counts for Lake Huron and Lake Superior from 1979 to 2005. Dashed line indicates projected nest counts for years with missing or incomplete data. (Source: Weseloh et al. 1995, 2002, 2006, Canadian Wildlife Service unpublished data, OMNR unpublished data, Shieldcastle unpublished data).

In contrast, cormorant populations on Lake Erie and the upper St. Lawrence River continue to show increasing trends over the last few years. In particular, the upper St. Lawrence River appears to have the fastest growing cormorant population in Ontario since 1997 (Weseloh et al. 2006). Lake Superior cormorant populations have remained relatively low and stable since 1997.


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Cormorant populations on the Great Lakes have been undergoing substantial changes over the past 5 years. Nest count data suggests that some regions are experiencing significant population increases, while others are experiencing decreases (Figure 4.1). Overall, the Great Lakes-wide cormorant population appears to be stabilizing in recent years (Table 4.1), which suggests the population may be responding to a newly established carrying capacity. Individual Great Lakes and the upper St. Lawrence River are discussed below separately. 4.1.1. LAKE SUPERIOR Lake Superior is bordered by four jurisdictions; Ontario, Michigan, Minnesota, and Wisconsin. Cormorants have been reported nesting in all four jurisdictions on Lake Superior and approximately 50 active nesting colonies have been identified lake-wide (Weseloh et al. 2006). Approximately 35 of these active colonies are found on the Ontario side of Lake Superior (Figure 4.2).

Figure 4.2 The distribution of cormorant colonies on Lake Superior in 2000 (Source: Weseloh et al. 2002).

On the Ontario side of Lake Superior, nest numbers have increased by nearly 40% from 1996 to 2005, but have only increased by approximately 10% since 1999 (Weseloh et al. 2006) (Figure 4.3). The nesting population on Lake Superior remains at very low numbers and densities relative to the other Great Lakes (Figure 4.1).

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Figure 4.3 Cormorant nest counts for Lake Superior (Ontario side only) from 1979 to 2005. Missing bars indicate years with missing or incomplete data. (Source: Weseloh et al. 1995, 2002, 2006, Canadian Wildlife Service unpublished data).


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4.1.2. LAKE HURON – GEORGIAN BAY Lake Huron is bordered by two jurisdictions; Ontario and Michigan. Cormorants have been reported nesting in both jurisdictions on Lake Huron and approximately 108 active nesting colonies have been identified lake-wide (Weseloh et al. 2006). Approximately 98 of these active colonies are found on the Ontario side of Lake Huron, with the vast majority being located in Georgian Bay and the North Channel (Figure 4.4).

Figure 4.4 The distribution of cormorant colonies on Lake Huron and Georgian Bay in 2000 (Source: Weseloh et al. 2002). Cormorant nesting populations on the Ontario side of Lake Huron have undergone dramatic increases since the late 1980s (Figure 4.5) (Weseloh et al. 1995, 2002, 2006, Korfanty et al. 1999). Lake Huron had one of the fastest growing cormorant populations on the Great Lakes in the late 1990s and peaked in 2000-2001. From 1997 to 2000, the nesting population on the Ontario side of Lake Huron grew by more than 60% and as many as 33 new nesting colonies were established (Weseloh et al. 2002). Since 2000, the Ontario nesting population has declined by more than 20% (Weseloh et al. 2006, OMNR unpublished data) (Figure 4.5).

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Figure 4.5 Cormorant nest counts for Lake Huron (Ontario side only) (red) from 1979 to 2005. Specific nest counts for Georgian Bay (blue) and the North Channel (orange) have been included to illustrate trends over time. Missing bars indicate years or locations with missing or incomplete data. * indicates only partial nest counts were completed in Georgian Bay and the North Channel (Source: Weseloh et al. 1995, 2002, 2006, Canadian Wildlife Service unpublished data, OMNR unpublished data).

Many fisheries and waterbird scientists have suggested that part of the reason for the decline in cormorant nesting populations on Lake Huron since 2000-2001 may be the result of lake-wide changes to the fish community. The Lake Huron alewife population index was extremely low in 2003 and 2004 (Schaeffer et al. 2006), which may suggest a plausible cause for the decline in cormorant nest counts (Ridgway 2005). Some stakeholders have suggested that the decline of alewife populations is a direct result of cormorant predation; however this is not the case. Alewife populations have experienced drastic declines across the lake-basin at locations where cormorants do not often occur (Ridgway et al. 2006, Schaeffer et al. 2006). In fact, alewife populations have experienced the slowest declines in Georgian Bay and the North Channel where cormorant populations are the most concentrated (Ridgway et al. 2006, Schaeffer et al. 2006, OMNR unpublished data). Fisheries scientists have suggested that the main reason for the decline in alewife populations is the result of recent severe winter conditions and abundant salmonid predators (Schaeffer et al. 2006).


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4.1.3. LAKE ERIE Lake Erie is bordered by five jurisdictions; Ontario, Ohio, Pennsylvania, New York, and Michigan. Cormorants have nested in four of the five jurisdictions on Lake Erie and approximately 10 active nesting colonies have been identified lake-wide (Weseloh et al. 2006). Five of these active nesting colonies are found on the Ontario side of Lake Erie. The majority of nesting colonies occur in the western basin of Lake Erie, where there are a number of uninhabited islands that provide suitable nesting habitat (Figure 4.6).

Figure 4.6 The distribution of cormorant colonies on Lake Erie in 2004 (Source: Weseloh and Havelka, Canadian Wildlife Service unpublished data).

Cormorant nesting populations on Lake Erie began showing significant increases in the late 1980s and early 1990s (Figure 4.7) (Weseloh et al. 1995, 2002, 2006, Korfanty et al. 1999). Lake Erie-wide nest numbers have increased by nearly 90% from 1997 to 2005 (Figure 4.7) (Weseloh et al. 2006). East Sister Island and Middle Island represent two of the largest nesting colonies in the Great Lakes basin, with both islands reporting over 6,000 cormorant nests in 2004 (Weseloh et al., in press). From 2004 to 2005, the Lake Erie nesting population declined by 8%, which was the first annual decline in cormorant nests on Lake Erie in more than 5 years (Figure 4.7) (Weseloh et al. 2002, 2006).

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Figure 4.7 Cormorant nest counts for Lake Erie (both Ontario and U.S. sides) from 1979 to 2005. Missing bars indicate years with missing or incomplete data. (Source: Weseloh et al. 1995, 2002, 2003, 2006, Canadian Wildlife Service unpublished data, Shieldcastle, M., Ohio Department of Natural Resources unpublished data).


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4.1.4 LAKE ONTARIO Lake Ontario is bordered by two jurisdictions; Ontario and New York. Cormorants nest in both jurisdictions on Lake Ontario and 26 active nesting colonies have been identified lake-wide (Weseloh et al. 2006). Twenty-two of these active nesting colonies reside on the Ontario side of Lake Ontario. The main nesting colonies occur in Burlington Bay, Toronto Waterfront, Presqu’ile Provincial Park, False Duck Islands, Kingston waterfront, and off Henderson Harbour (New York) (Weseloh and Shutt 2005). There are no colonies on the south shore of Lake Ontario at this time (Figure 4.8).

Figure 4.8 The distribution of cormorant colonies on Lake Ontario in 2005 (Source: Weseloh and Havelka, Canadian Wildlife Service unpublished data 2005).

The Lake Ontario cormorant population has been closely monitored in the past (Price and Weseloh 1986, Weseloh and Ewins 1994, Blackwell et al. 2002, Weseloh et al. 2003). The first recorded incident of cormorant nesting on Lake Ontario occurred on Scotch Bonnet Island in 1938-1939; however substantial population increases did not occur until the mid-1980s (Baillie 1947, Weseloh and Shutt 2005). In 2002, the Lake Ontario nesting population peaked at approximately 28,000 cormorant nests (Figure 4.9). Eight new colonies were established and nest numbers increased by more than 70% from 1997 to 2002, but have since decreased by 17% to approximately 23,500 nests lake-wide (Figure 4.9) (Weseloh et al. 2006). From 2004 to 2005, the Lake Ontario nesting population declined by approximately 10% (Figure 4.9).

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Figure 4.9 Cormorant nest counts for Lake Ontario (both Ontario and U.S. sides) from 1979 to 2005. (Source: Weseloh et al. 1995, 2002, 2003, 2006, Canadian Wildlife Service unpublished data).

Active cormorant management and research programs (i.e., nest removal, egg oiling, and culling activities) have been conducted by the Ontario Ministry of Natural Resources and New York States Department of Environmental Conservation at some of the large nesting colonies on Lake Ontario, including Presqu’ile Provincial Park (Ontario) and Little Galloo Island (New York). In 2004, both Ontario and New York initiated a cormorant culling program in the eastern basin of Lake Ontario (High Bluff Island and Little Galloo Island), which may be responsible for the recent population declines.


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4.1.5 ST. LAWRENCE RIVER The upper St. Lawrence River is bordered by three jurisdictions: Ontario, Quebec, and New York. Cormorants nest in all three jurisdictions along the upper St. Lawrence River and approximately 16 active nesting colonies were identified river-wide in 2005 (Weseloh et al. 2006). Approximately 11 of these active nesting colonies reside on the Ontario side of the upper St. Lawrence River (Figure 4.10).

Figure 4.10 The distribution of cormorant colonies on the upper St. Lawrence River in the jurisdictions of Ontario, Quebec, and New York State in 2005. (Source: Weseloh and Havelka, Canadian Wildlife Service unpublished data 2005).

Cormorants were first reported in the upper St. Lawrence River in 1945 (Weseloh and Collier 1995); however cormorants were known to be nesting in the lower St. Lawrence as early as the beginning of the century (Townsend and Bent 1910, Lewis 1929). Cormorants abandoned the upper St. Lawrence River during the 1950s – 1960s, and then returned and began nesting on Strachan Island in the early 1990s (Weseloh et al. 2002) By the mid-1990s, three known cormorant colonies had been established in the upper St. Lawrence River, totalling approximately 400 nests (Weseloh et al. 2002). Since 1997, approximately 10 new nesting colonies have been established and nest numbers have

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increased by more than 300% along the upper St. Lawrence River (Figure 4.11) (Weseloh et al. 2006). Increased nest numbers have occurred on both the Canadian side (i.e., Ontario and Quebec) and the United States side of the river, however the majority of the increase has occurred in Ontario due to available nesting habitat. Weseloh et al. (2006) reported several cases of recent unsanctioned control activities at cormorant colonies in this area. From 2004 to 2005, nest numbers increased by approximately 6% along the upper St. Lawrence River (Weseloh et al. 2006).

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Figure 4.11 Cormorant nest counts for the upper St. Lawrence River (both Canadian and U.S. sides) from 1991 to 2005. Missing bars indicate years with missing or incomplete data. (Source: Weseloh et al. 2002, 2006, Canadian Wildlife Service unpublished data).


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4.2 INLAND LAKES Our knowledge of the status of double-crested cormorant populations on inland lakes in Ontario is incomplete. It is difficult to assess the status of cormorants on inland lakes because of the sheer size of potential nesting area and the vast number of inland lakes across the province. The isolation of many of Ontario’s inland lakes makes it difficult to assess inland lake populations on a broad-scale. Movement between lakes is common, with cormorants typically residing on a lake (or group of lakes) for relatively short periods of time to feed and loaf. Cormorants may show less interest and fidelity to nest sites on inland lakes than on the Great Lakes (Alvo et al. 2002, OMNR unpublished data). This may be because of a reduced quality of nesting sites and a smaller forage base on inland lakes. Nevertheless, there are substantial cormorant colonies residing on some inland lakes in Ontario. Responding to the movement of cormorants from the Great Lakes into smaller inland lakes the OMNR updated its inland lake information. The current population status for inland lakes has been obtained from province-wide OMNR surveys, limited primary research, and from the Ontario Breeding Bird Atlas (Cadman et al. 1987, OMNR 1997, Alvo et al. 2002, Rowe 2003, OBBA 2005) (described in more detail in section 6.7 Inland Lake Monitoring). Available information suggests that approximately 40 inland lakes in Ontario have confirmed cormorant nesting populations. The cormorant population status for inland lakes has been assessed and reported in more detail for OMNR’s three management regions; Northwest Region, Northeast Region, and Southern Region (Figure 4.12).

Figure 4.12 The Ontario Ministry of Natural Resources three provincial management regions. (Source: Provincial Geomatics Service Centre, 2002).


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4.2.1 NORTHWEST REGION Cormorants have resided on large inland lakes in the Northwest Region for hundreds of years (Peck and James 1983). Two of the largest inland breeding populations in Ontario reside in northwest region on Lake Nipigon and Lake of the Woods. The breeding populations on both these lakes number in the thousands of nests. Cormorant populations on Lake Nipigon and Lake of the Woods are likely the largest contributors to inland lake populations in the interior of northwest region, whereas Lake Superior likely contributes heavily to inland lake populations along its coast. It is not uncommon to see large (100+ birds) foraging flocks on inland lakes that are relatively close to Lake Superior or other major inland waterbodies (i.e., Lake Nipigon, Lake of the Woods, Rainy Lake). Available information suggests that foraging and nesting on inland lakes has increased over the past twenty years in Northwest Region, but not to the same degree as it has in other regions of the province (Cadman et al. 1987, OMNR 1997, OBBA 2005). To date, approximately 10 inland waterbodies have confirmed cormorant nesting in northwest region (Figure 4.13).

Figure 4.13 Inland lakes or waterbodies where cormorant nesting has been confirmed in the Ministry of Natural Resources Northwest Region.

The largest inland nesting colonies occur on the largest waterbodies in the region, including Lake Nipigon, Lake of the Woods, and Rainy Lake (Figure 4.13). Although these nesting colonies have been established for some time, continuous annual lake-wide


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population trend data are not available. Other smaller nesting colonies have been observed on Lac Seul, Lake Onaman, Sturgeon Lake, Namakan Lake, and Helen Lake. The most northerly inland nesting colony in Ontario occurs on Little Sachigo Lake, where approximately 80 nests were reported by the Ontario Breeding Bird Atlas in 2005 (OBBA 2005). 4.2.2 NORTHEAST REGION Cormorant populations on inland lakes in the Northeast Region are probably strongly influenced by the nesting populations on Georgian Bay and the North Channel of Lake Huron. In recent years, it appears that these inland nesting populations have stabilized, possibly as a result of population declines on Lake Huron (primarily Georgian Bay and the North Channel) since 2000-2001 (Weseloh et al. 2006, OMNR unpublished data). Cormorants have nested on Lake Abitibi in Northeast Region since about 1935 (Armstrong 1984). It wasn’t until the early to mid-1990s when cormorants began nesting in small numbers on other inland lakes in northeast region (Peck and James 1983, Armstrong 1984, Alvo et al. 2002, Rowe 2003). Since then, a number of new nesting colonies have been established and small numbers of foraging cormorants have become more common in the region. To date, approximately 10 inland waterbodies have confirmed cormorant nesting colonies in Northeast Region (Figure 4.14).

Figure 4.14 Inland lakes or waterbodies where cormorant nesting has been confirmed in the Ministry of Natural Resources Northeast Region.


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The largest inland nesting colonies occur on the largest waterbodies in the region, including Lake Nipissing and Lake Abitibi (Figure 4.14). Other small nesting colonies have been observed on Lake Manitou, Kelley Lake, Wanapitei Lake, Obabika Lake, Nighthawk Lake, and Saganash Lake. Lake Nipissing has the largest inland breeding population of cormorants in the Northeast Region. Population monitoring surveys indicate that there are four established breeding colonies on Lake Nipissing (Rowe 2003). Since 1999, the Lake Nipissing nesting population appears to be relatively stable, fluctuating around 2000 nests lake-wide (Rowe 2003, OMNR unpublished data).

Photo credit: J. Stewart

4.2.3 SOUTHERN REGION Great Lakes cormorant populations have a large effect on inland populations in Southern Region. The region is bordered by Lake Ontario and Lake Huron/Georgian Bay, which contain the two largest basin-wide cormorant populations in Ontario. Lake Erie and the upper St. Lawrence River also influence inland cormorant populations in southern region, but likely to a lesser degree. Population increases on the Great Lakes and its connecting waterbodies have generally coincided with population increases on inland lakes in southern Ontario. Over the past several years there has been an increase in the number of foraging and nesting cormorants on inland lakes. In 1987, the Ontario Breeding Bird Atlas reported no confirmed cormorant breeding outside of the Great Lakes in the Southern Region (Cadman et al. 1987). Cormorants have since expanded to establish a number of new breeding colonies on inland waterbodies (OBBA 2005); however the vast majority of foraging and nesting still occurs along the Great Lakes coastline. To date, approximately 20 inland waterbodies have confirmed cormorant nesting colonies in Southern Region (Figure 4.15).


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Figure 4.15 Inland lakes or waterbodies where cormorant nesting has been confirmed in the Ministry of Natural Resources Southern Region.

The largest inland nesting colonies in Southern Region occur on larger waterbodies adjacent to the Great Lakes, including Lake Simcoe, Lake Couchiching, and Rice Lake. Small groups (1 – 10 birds) of transient foraging cormorants are commonly seen throughout smaller lakes from April to October. Larger (50+ birds) resident foraging flocks are known to occur on Lake Simcoe, Lake Couchiching, the Muskoka Lakes, the Kawartha Lakes, Rice Lake, Golden Lake, and Lake Opeongo.


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5.0 CONCERNS ABOUT CORMORANTS IN ONTARIO Double-crested cormorants are a native species and a natural part of Ontario’s ecosystem. Over the past several years, increasing cormorant populations in Ontario have led to growing concerns from the public, including requests for control programs. These concerns include impacts on fisheries, vegetation, other species, and human socio-economic values. Although cormorants are a natural and valuable component of the ecosystem their rapid range expansion, population growth and large numbers in some areas have caused real and/or perceived conflicts with some stakeholders and ecological impacts to ecosystems at varying scales. This section of the report explores these concerns based on the most recent available knowledge. 5.1 IMPACTS ON FISH There is a perception by some stakeholder groups and individuals that fish predation by cormorants is detrimental to recreational and commercial fisheries in Ontario and throughout the United States (OMNR 1997, Belyea et al. 1999, Korfanty et al. 1999, Wires et al. 2001, Van De Valk 2002, Rudstam et al. 2004). Cormorants are opportunistic feeders that prey on the most abundant and easy to catch fish (Ludwig et al. 1989, Neuman et al. 1997, Hatch and Weseloh 1999). Over 250 fish species from more than 60 families have been reported as cormorant prey items (Hatch and Weseloh 1999). Bioenergetics studies and supporting literature suggest that cormorants consume approximately 20 – 25% of their body mass in fish daily (Dunn 1975, Schramm 1984, Cummings 1987, Glahn and Brugger 1995). On Lake Ontario, where cormorants averaged 1.9 kg (N= 40, unpubl. data D. Tyerman/D.V. Weseloh), this would mean a daily consumption of approximately 0.38 - 0.48 kg. As such, it is generally accepted that an adult cormorant will consume approximately 0.45 kg (~ 1 pound) of fish daily (range of estimates 0.30 kg – 0.60 kg) (Wetmore 1929, Schramm et al. 1984, Cummings 1987, Weseloh and Casselman 1992, 1994, Glahn and Brugger 1995, Hatch and Weseloh 1999, Glahn and Dorr 2002, Glahn and King 2004). Adult cormorant daily fish consumption will vary with body mass, age, caloric content of diet, environmental temperatures, breeding status, and locality (Montevecchi and Piatt 1987, Brugger 1993). Many other birds (e.g., mergansers, scaup, herons, kingfishers, gulls, terns, loons, etc.) are also capable of consuming large quantities of fish (Madenjian and Gabrey 1995); however cormorants generally forage with more concentrated intensity in local areas (i.e., < 5 km of nesting colony) than other resident birds (e.g., herons, egrets, gulls, kingfishers, loons, etc.) and for longer periods of time than other migrant birds (e.g., mergansers, scaup, etc.) (Hebert and Morrison 2003). Migrant red-breasted mergansers (Mergus serrator) were estimated to consume more annual lake-wide fish biomass than cormorants on Lake Erie in the mid-1990s; however cormorants were responsible for the greatest total fish consumption in the western basin, suggesting a more concentrated local


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fish consumption by cormorants in the areas surrounding their major nesting colonies (Stapanian et al. 2002, Hebert and Morrison 2003). Gulls are also extremely abundant in the Great Lakes region; however impacts to fisheries remain of relatively little public concern because their feeding is limited to surface waters and they consume a wide range of food items. Cormorants are often condemned by some members of the recreational and commercial fishing community as being one of the main causes for the decline in some Great Lakes fish populations. Various studies have shown that cormorants can have an impact on fish abundance and production (Schneider et al. 1996, 1998, Neuman et al. 1997, Burnett et al. 2002, Collis et al. 2002, Johnson et al. 2002, Lantry et al. 2002, Stapanian et al. 2002, Rudstam et al. 2004); however, there has been no evidence to suggest that cormorants have been responsible for the demise of any species in the Great Lakes-wide fish community. A number of other environmental factors have contributed to basin-wide fish community changes including, invasion of exotic species (i.e., sea lamprey, zebra mussels, round goby, etc.), non-native species introductions (i.e., alewife, rainbow smelt, Pacific salmonids, etc.), loss of spawning habitat, toxic contaminants, over-fishing, climate change, weather patterns, and changes to water quality (Crowder 1986, Kaufman 1992, Mills et al. 1993, Koonce 1995, Ricciardi 2001, Mills et al. 2005). Fundamental shifts in food-web interactions and changes to nutrient and energy dynamics in the Great Lakes are having the greatest impact on changes to its fish community (Ewins 1994, Koonce 1995). Numerous fisheries-related studies have been conducted to assess the impacts of cormorants on fish communities and populations over the past 10 years (Ross and Johnson 1995, Blackwell et al. 1997, Derby and Lovvorn 1997, Neuman et al. 1997, Belyea et al. 1999, Trapp et al. 1999, Simmonds et al. 2000, Wires et al. 2001, Van De Valk et al. 2002, Rudstam et al. 2004). However, there are some major differences in the interpretation of research results, particularly among stakeholders. Impacts on fisheries can vary considerably depending on species, community-type, age class, locality, and scale of the assessment, which may lead to the observed confusion. Trapp et al. (1999) and Wires et al. (2001) conducted extensive literature reviews on the diet of cormorants and found that, in general, recreational and commercial fish species do not substantially contribute to the diet of cormorants and are not negatively affected; however, both reviews cited specific exceptions. Studies have shown that spatial, temporal, and seasonal variation of prey populations have a major influence on cormorant habitat use and diet composition (Blackwell et al. 1997, Neuman et al. 1997, Belyea et al. 1999, Burnett et al. 2002, Stapanian et al. 2002). Interpretation of cormorant diet analysis must be approached with caution because of these variations and extrapolations to a lake-wide context can only be made meaningful if spatial and temporal variability has been quantified (Neuman et al. 1997, Wires et al. 2001). Research on the Great Lakes has repeatedly shown that cormorants feed primarily on small, shallow water fish, that are of relatively low economic and commercial value, including alewife (Alosa pseudoharengus), rainbow smelt (Osmerus mordax), gizzard


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shad (Dorsoma cepadianum), white suckers (Catostomus commersoni), pumpkinseeds (Lepomis gibossus), sticklebacks (Gasterosteidae sp.), and Cyprinid species (Ludwig et al. 1989, Weseloh and Casselman 1992, Weseloh and Ewins 1994, Weseloh and Collier 1995, Neuman et al. 1997, Bur et al. 1999, Johnson et al. 1999, Trapp et al. 1999, Wires et al. 2001, Ratcliff 2004). In general, game species such as salmonids, smallmouth bass (Micropterus dolomieu), yellow perch (Perca flavescens), and walleye (Sander vitreus) have comprised a relatively small percentage of cormorant diet (Craven and Lev 1987, Montevecchi et al. 1988, Karwowski 1994, Ross and Johnson 1994, Belyea et al. 1999, Bur et al. 1999, Trapp et al. 1999, Wires et al. 2001, Hebert and Morrison 2003, Ratcliff 2004). However, as previously mentioned, studies suggest that considerable spatial, temporal, and seasonal variation may exist in the diet of Great Lakes cormorants and these generalizations do not always apply (Neuman et al. 1997, Burnett et al. 2002, Johnson et al. 2002, Stapanian et al. 2002). For example, Lantry et al. (2002) noted that cormorants consume large quantities of smallmouth bass and yellow perch at certain times of the year in the waters near Little Galloo Island in Lake Ontario. Johnson et al. (2003, 2004) also found that yellow perch dominated the diet of cormorants at some colonies in the upper St. Lawrence River. Direct impacts from cormorant predation on larger game fish may be almost non-existent, as cormorants generally consume fish that are up to approximately 15cm in length (Craven and Lev 1987, Weseloh and Ewins 1994, Hatch and Weseloh 1999). In some cases, there have been measurable impacts to younger age class sport fish (Belyea et al. 1999, Eckert 1999, Van De Valk et al. 1999, Collis et al. 2002, Lantry et al. 2002, Van De Valk et al. 2002, Rudstam et al. 2004). Rudstam et al. (2004) and Van De Valk et al. (1999, 2002) conducted studies on walleye and yellow perch stocks in Oneida Lake, New York, and found that while adult walleye exploitation was attributed to angling, the exploitation of sub-adult walleye was almost entirely attributed to cormorant predation. Lantry et al. (2002) also reported similar findings indicating that cormorant predation on 3-5 year old age classes of smallmouth bass was substantial enough to cause observed declines in local populations in eastern Lake Ontario. Increased rates of mortality in younger year classes may severely limit the numbers of adult stock recruited to the fishery (Collis et al. 2002, Lantry et al. 2002, Rudstam et al. 2004). Belyea et al. (1999) noted that cormorant predation accounted for a greater proportion of mortality in young yellow perch, while angling accounted for a greater proportion of mortality in older yellow perch, but ultimately concluded that cormorant predation had a minimal impact on local Les Cheneaux Island perch populations during their study. In general, cormorants will seldom take valuable recreational or commercial fish species, such as walleye, smallmouth bass, lake whitefish (Coregonus clupeaformis), lake trout (Salvelinus namaycush), and other salmonids despite recent population increases (Roney 1979, Craven and Lev 1987, Hobson et al. 1989, Trapp et al. 1999, Wires et al. 2001, Ratcliff 2004). Recreational and commercial fish species are rarely found to be directly impacted by foraging cormorants, except in circumstances where the scale of assessment is small and/or the location is relatively unproductive for forage fish. For example, there is concern in some Algonquin Park lakes that foraging flocks of cormorants may cause


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significant impacts to brook trout (Salvelinus fontinalis) populations, because these lakes are small, isolated and relatively unproductive (Quinn et al. 1994, Vascotto 2004). Although no substantial impact to fisheries have been detected on a Great Lakes basin-wide scale (Weseloh and Casselman 1992, Jones et al. 1993, Weseloh and Casselman 1994), there is considerable evidence to suggest that cormorant predation can have direct impact on fisheries in specific areas (Schneider et al. 1996, 1998, Burnett et al. 2002, Edwards and Stewart 2002, Lantry et al. 2002, Rudstam et al. 2004). Birt et al. (1987) demonstrated a central foraging theory at large breeding colonies by showing that cormorants will create prey-depleted halos around colonies, and then gradually move further and further away to forage as prey are depleted locally. Glanville (1992) reported that cooperative fishing activity by cormorants in small bays and inlets may significantly increase the impacts to local near-shore fisheries. Edwards and Stewart (2002) observed localized impacts to fish communities in close proximity to the High Bluff Island cormorant colony, however these impacts were not reflected at sites over 25 km from the colony. In some cases, cormorants have also been found to have a direct local impact on fisheries during stocking programs when young salmonids are released into lakes or rivers (Meister and Gramlich 1967, Blackwell et al. 1997, Derby and Lovvorn 1997, Ross and Johnson 1999). Wiese et al. (2001) suggested that avian predation at stocking sites may be beneficial to salmonid smolts during certain periods because they would also consume large numbers of predatory fish. Impacts to fish communities in reservoirs or small ponds may also be significant as a result of concentrated cormorant foraging. Simmonds et al. (2000) modeled the effects of cormorant predation on sport and forage fish populations in reservoirs and showed that under specific circumstances, cormorants could significantly reduce fish populations where they remain throughout the migration and wintering period. However, Simmonds et al. (2000) concluded that in most cases cormorant predation typically had only minor or inconsequential impacts on recreational fisheries in reservoirs because sustained concentrations of foraging cormorants at these small waterbodies is uncommon. Numerous studies have been conducted in the southern United States to assess the impacts to aquaculture fisheries due to cormorant predation (Stickley et al. 1992, Brugger 1995, Glahn et al. 1995, Wywialowski 1999, Glahn et al. 1999, Glahn and Dorr 2002, Dorr et al. 2004). Many cormorants that nest and feed in the Great Lakes spend winter in the Delta region of the Mississippi, which is the center of the catfish aquaculture industry (Brunson 1991). Glahn et al. (1995) noted that the growth of the southern U.S. aquaculture industry has been paralleled by burgeoning cormorant populations (Vermeer and Rankin 1984, Hobson et al. 1989, Dolbeer 1990). Researchers have long speculated that cormorants are experiencing improved body condition and increased in winter survival due to the artificially inflated forage base provided by catfish aquaculture facilities (Vermeer and Rankin 1984, Weseloh and Ewins 1994, Duffy 1995). Glahn et al. (1999) confirmed that pre-migratory cormorants from the Delta region of the Mississippi are in better body condition than cormorants from areas with no aquaculture industry. Impacts on aquaculture fisheries due to cormorant predation have been locally severe in the southern United States (Craven and Lev 1987, Stickley et al. 1992, Brugger


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1995, Glahn et al. 1995, Wywialowski 1999). Aquaculture facilities and hatcheries have sustained high losses of fingerlings, stocking fish and food fish from increasing cormorant populations (Stickley et al. 1992, Brugger 1995, King et al. 1995). Glahn et al. (1995) reported some wintering cormorant diets that were comprised of >90% channel catfish (Ictalurus punctatus) and gizzard shad. Wires et al. (2001) reported that cormorants can consume large numbers of aquaculture and hatchery reared fish, both locally and temporally. Cormorants are generalist predators whose diet varies considerably between seasons and locations. In general, cormorant predation has not been found to have a significant impact on Great Lakes sport or forage fish populations on a lake-wide scale. However, researchers have also found that cormorants can have significant impacts on sport and/or forage fish populations at some locations depending on the species, age class, season, and scale of analysis. 5.2 IMPACTS ON VEGETATION Cormorant colonies can cause significant negative impacts to vegetation at nesting and roosting sites. These localized impacts can include physical and/or chemical damage to vegetation and soil. “Whitewashing” from the deposition of guano (faeces) and associated ecological changes to their surrounding habitat is often cited as the major concern for vegetation at cormorant colonies (Lemmon et al. 1994, Wires et al. 2001, USFWS 2003). Vegetation and habitat damage includes loss of both structural and species diversity. Physical Impacts Physical damage to vegetation and trees is caused by cormorants breaking branches and removing foliage to collect nesting materials (i.e., leaves, twigs and branches) during the breeding season (Lemmon et al. 1994, Aderman and Hill 1995, Hobara et al. 2001). The weight of cormorant nests can also cause branches and limbs to break. Several studies have documented the physical impact of cormorant nesting colonies on the forest canopy (Koh and Car 2003, Rippey et al. 2002, Hebert et al. 2005, Koh 2005). Loss of canopy cover and plant diversity may occur on islands where cormorants nest (Bédard 1988, Chapdelaine and Bédard 1995, Rippey et al. 2002). As cormorant populations expanded at the Presqu’ile Provinical Park islands and the western islands of Lake Erie, significant reductions in forest canopy were documented over a relatively short period of time (Hebert et al. 2005, Koh 2005). Other large tree nesting birds, such as the great blue heron (Ardea herodias) can also cause physical impacts to vegetation; however impacts from cormorants appear to occur more extensively and with greater intensity (Weseloh and Brown 1971, Dusi 1978, Weseloh, per. comm., 2005). Over time, cormorants will typically kill trees on selected nesting sites (Lemmon et al. 1994, Bédard 1995). This is exemplified by research conducted at High Bluff Island, Presqu’ile Provincial Park, which showed that


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cormorants will adapt to available nesting habitat in a colony by moving nesting sites down the canopy and onto the ground as large and then small trees are killed (Shieldcastle and Martin 1999, Koh and Carr 2003, Hebert et al. 2005, Koh 2005). Other colonial nesters will typically abandon an area or move to another location once the prime nesting trees/areas are gone. In these cases, the mid-canopy is left to regenerate the upper canopy (Koh 2005). Chemical Impacts Cormorant guano can also cause detrimental impacts to surrounding vegetation and trees (Lemmon et al. 1994, Bédard et al. 1995, Wires et al. 2001). The following paragraph describes some chemical impacts and has been summarized from Hebert et al. (2005). Cormorant guano changes the soil chemistry at breeding colonies by increasing concentrations of phosphorus, nitrogen, and potassium (Ligeza et al. 2000, Hobara et al. 2001, Cuthbert et al. 2002, Ellis et al. 2006). Elevated levels of ammonium have been reported in soils and nitrogen is taken up by plants (Lemmon et al. 1994, Kameda et al. 2000, Hobara et al. 2001, Ellis et al. 2006). Uptake of excess ammonium can result in plant toxicity, particularly in areas where soil pH is low (Hogg and Morton 1983, Britto and Kronzucker 2002). Soils within cormorant colonies have been reported to be more acidic than soils from reference areas, which reflects the acidifying effects of concentrated guano deposition (Ishida 1996, Cuthbert et al. 2002). In addition, ammonium toxicity in plants may be exacerbated under conditions of low humidity and high wind velocity, which are environmental conditions typical of Great Lakes islands (Krastina and Loseva 1975, Haynes and Goh 1978). These effects are magnified progressively as tree stands become less dense and the microclimate of the forest becomes increasingly dry, hot and windy. Considering these findings, ammonium toxicity may be an important factor contributing to island forest declines. Cormorant guano is also known to inhibit photosynthesis in plants and trees from the adhesion of excrement to leaf surfaces in dense breeding colonies, which contributes to the decline and mortality of vegetation (Ishida 1997). Other colonial nesting birds are capable of causing significant impacts to vegetation at nesting colonies; however Ellis et al. (2006) noted that nesting densities of cormorants are typically much higher than other colonial nesting birds (e.g., black-backed gulls). Changes in Vegetation and Diversity A combination of physical impacts (i.e., loss of canopy cover, tree mortality, etc.) and chemical impacts (i.e., effects of guano, tree mortality, etc.) can cause significant changes to native vegetation and plant diversity (Bédard 1988, Chapdelaine and Bédard 1995, Rippey et al. 2002). Changes in vegetation species and structural diversity have been reported at a number of sites in and around Ontario, including Golden Lake near Pembroke, Three Sisters Islands in Lake of the Woods, Nottawasaga Island near Collingwood, the Flower Pot Islands in Batchawana Bay (Lake Superior), East Sister


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Island Provincial Nature Reserve and Middle Island in Lake Erie, and Pigeon Island, Little Galloo Island, the Brother Islands, Snake Island, Scotch Bonnet Island, Gull Island and High Bluff Island in Lake Ontario. Woodlots on Gull Island and along the southern edge of High Bluff Island have disappeared since cormorant colonization began. Vegetation studies on High Bluff Island during the period of 2000 to 2004 have demonstrated a decline in woodlot health, including an increase in the proportion of dead standing trees (i.e., 17% tree mortality from 2000 to 2002) (Carr and Koh 2001, Koh and Carr 2003, Koh and Hogsden 2006). Similar changes to the plant community have been observed on the islands in western Lake Erie since major cormorant colonization (Kamstra et al. 1995, Hebert et al. 2005). There has been an overall loss of herbaceous vegetation diversity, which has resulted in a community largely composed of invasive native and non-native species, such as pokeweed (Phytolacca americana), garlic mustard (Alliaria petiolata) and common goosefoot (Chenopodium alba) (Crins and Oldham 2000). Loss of native plant diversity can lead to the establishment of exotic species tolerant of over-fertilization (Rippey et al. 2002, Weseloh et al. 2002, Koh 2005). Monocultures of such species can lead to reductions in plant species richness and the diversity of habitats available for other wildlife (Chapdelaine and Bédard 1995, Rippey et al. 2002, Koh 2005). Cormorant nesting colonies can cause increased mortality of nationally and provincially significant vegetation species (i.e., species that are rare or at risk). Inventory studies on East Sister Island Provincial Nature Reserve in Lake Erie have documented the presence of rare species and species at risk (Tracey et al. 1971, Kamstra et al. 1995, Crins and Oldham 2000). Hebert et al. (2005) reported mortality of the nationally threatened Kentucky coffee tree (Gymnocladus dioicus) on East Sister Island Provincial Nature Reserve (COSEWIC 1992, White and Oldham 2000). Increased mortality of Kentucky coffee trees was also reported on the western Lake Erie islands since cormorant nesting colonies were established (Crins and Oldham 2000). Hebert et al. (2005) suggested that tree nesting cormorants were likely responsible for recent declines in forest cover on these islands. 5.3 IMPACTS ON OTHER SPECIES Cormorants can affect a wide variety of co-occurring terrestrial species. Impacts on other species may include species mortality, loss of habitat and increased competition. Mortality and Loss of Habitat Cormorant nesting colonies may cause significant mortality to vegetation (as discussed in Section 5.2 Impacts on Vegetation), including nationally and provincially significant species (Carr and Koh 2001, Koh and Carr 2003, Hebert et al. 2005, Koh and Hogsden 2006). Crins and Oldham (2000) reported the absence of a number of rare species that were previously found on the western Lake Erie islands prior to the establishment of major cormorant nesting colonies.


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Previous research conducted in the Great Lakes basin indicates that persistent vegetation destruction at cormorant nesting colonies can result in habitat loss (Crins and Oldham 2000, Carr and Koh 2001, Wires et al. 2001, Weseloh et al. 2002, Koh and Carr 2003, Hebert et al. 2005, Koh 2005). Habitat loss through the reduction of forest canopy, structural and species diversity may result in a loss of nesting, roosting and feeding habitat for other forest dwelling birds, migrating species, and some colonial nesting species. Shieldcastle and Martin (1999) reported declines in great blue heron, great egret and black-crowned night-heron populations with the arrival of cormorants on West Sister Island in Lake Erie from 1991 to 1997. These declines were attributed to habitat loss through natural vegetative succession and cormorant caused habitat degradation. Research indicates that cormorants can better adapt to changing and/or deteriorating habitats than other colonial birds can (Grieco 1999, Shieldcastle and Martin 1999, Koh and Carr 2003). The forest vegetation of High Bluff Island at Presqu’ile Provincial Park and the western Lake Erie islands are used by a variety of birds and other wildlife (e.g., monarch butterflies, Danaus plexippus) during migration (Mineau and Markel 1979, LaForest 1993). As well, the endangered Lake Erie watersnake (Nerodia sipedon insularum) is found on both East Sister Island and Middle Island in Lake Erie (Kamstra et al. 1995, Crins and Oldham 2000). The use of these islands by migrating species and the survival of nationally and provincially significant terrestrial species may be jeopardized by loss of suitable habitat conditions as a result of cormorant nesting colonies. Changes in the condition of the forest floor microhabitat (i.e., light penetration, moisture and temperature) will affect both plants and animals associated with these habitats. Competition Cormorants may compete directly for nest sites with other colonial nesting waterbirds (Moore et al. 1995, Shieldcastle and Martin 1999, Wires et al. 2001, Weseloh et al. 2002, Weseloh et al. 2005). Cormorants, gulls and terns all nest on the ground on islands in the Great Lakes basin (Blokpoel and Tessier 1996, Scharf and Shugart 1998). The impact of cormorants on other species of ground nesting birds is largely unknown, although there is some evidence of cormorants displacing herring gulls (Larus argentatus) at a colony in Hamilton Harbour in western Lake Ontario (Somers et al. in review, Weseloh, pers. comm., 2005). There is documented evidence of competition for nests and nesting sites between cormorants and three heron species; the great blue heron (Ardea herodias), the great egret (Casmerodius albus), and the black-crowned night-heron (Nycticorax nycticorax) (Moore et al. 1995, Quinn et al. 1996, Jarvie et al. 1999, Shieldcastle and Martin 1999, Wires et al. 2001, Weseloh et al. 2002, 2005, OMNR 2003, 2004a, 2005b). Moore et al. (1995) and Jarvie et al. (1999) documented movement of black-crowned night-herons colonies in response to cormorant nesting activities in Hamilton Harbour and Tommy Thompson


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Park in Lake Ontario. Wires et al. (2001) concluded that cormorants may displace other waterbirds from individual colonies, although no studies have demonstrated regional or population impacts on other colonial waterbirds. Cuthbert et al. (2002) concluded that with the exception of specific circumstances, the presence of cormorants has not caused heron declines or abandonment on the U.S. Great Lakes. Weseloh et al. (2002) suggested that cormorant nesting could impact other colonial waterbirds in specific circumstances by: a) reducing the amount of available nesting space if there is a substantial increase in cormorant nesting on a small island, b) direct competition for nesting sites where cormorants take-over nests, c) indirect displacement from tree nesting activities when cormorants establish nests above other colonial birds in the canopy (i.e., falling guano and debris may cause herons to abandon nests). The displacement of black-crowned night-heron colonies as cormorants begin to nest at the same location has been well documented on Lake Ontario (Moore et al. 1995, Blokpoel and Tessier 1996, Jarvie et al. 1999, Weseloh et al. 2002). Observations by Ontario Parks staff on High Bluff Island at Presqu’ile Provincial Park have also indicated that there is some direct competition for nest sites and nests between cormorants and heron species. Richards (1989) reported that cormorants had moved into a black-crowned night-heron rookery on the south side of High Bluff Island and taken over all of the high nesting sites, forcing the herons to nest in less desirable sites closer to the ground. Observations of active competition for nests between cormorants and heron species occurred on High Bluff Island during monitoring in 2003, 2004 and 2005, where cormorants have been observed driving egrets and herons from their nests (OMNR 2003, OMNR 2004a, OMNR 2005b). 5.4 IMPACTS ON HUMANS Wildlife populations provide a broad range of economic, social and cultural benefits to Ontario residents. These include direct benefits related to consumptive and non-consumptive use (e.g., viewing, hunting, tourism marketing, commercial harvests, etc.) and the indirect benefits of knowing wildlife is part of the natural ecosystem (e.g., biodiversity, bequest to following generations, etc.) (Bishop 1987). Public debate with respect to conflicts between humans and wildlife (perceived or otherwise) engenders different philosophical opinions, economic debates and expression of personal values with respect to the best ways to reduce conflicts. A strategy for addressing human-wildlife conflicts in Ontario is being developed to better understand and address some of these issues. Research has documented varying degrees of cormorant impacts on fish, vegetation, and other species (see sections 5.1 Impacts on Fish, 5.2 Impacts on Vegetation, 5.3 Impacts on Other Species). Social scientists and economists have also been able to estimate the range of social impacts on humans by documenting “use values” associated with wildlife. Use values are those benefits that are associated with the use of a resource. Traditionally, use values have been grouped into consumptive and non-consumptive categories.


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Consumptive use values can include an angler deriving benefits from the fishing activity, and from occasionally catching a fish; a hunter deriving benefits from the hunting activity and from occasionally taking sought after game. These types of use values contain a complex mixture of recreational, social, cultural, food and economic benefits. Passive (i.e., non-consumptive) use values do not involve a person’s quest for ultimate possession of an individual wildlife species. For example, a bird watcher derives benefit from searching for, and observing a particular bird species; a cottager/camper derives benefit from incidentally observing or hearing wildlife. Passive use values include being able to view or hear species in their natural habitat. Consumptive and non-consumptive use values are not mutually exclusive. Both consumptive and non-consumptive use values encompass a broad range of wildlife values that are based an individual’s personal experience and beliefs. These values can include the belief that wildlife resources must be passed on to future generations; preserving options for using the resource in the future; or simply that preservation of a resource is the right thing to do (USFWS 2003). While intangible, these are firmly held beliefs and underscore the fact that there are clear social benefits associated with the continued presence of wildlife in Ontario, including cormorants. Some Ontarians have expressed their concern with the government’s decision to manage cormorant populations at Presqu’ile Provincial Park. They philosophically disagree with direct intervention to reduce cormorant populations in what they believe is a natural population fluctuation or recovery, and in some areas they are concerned about the continued future health of cormorant populations. Other Ontarians have expressed concerns regarding negative economic, social and ecological impacts associated with the presence of large cormorant populations (Ewins 1994). Potential socio-economic impacts may include economic losses to aquaculture producers, commercial fisheries, and fishing-related businesses, losses to private resources (including fish in private lakes and damaged trees), and compromised local water quality (USFWS 2003). These individuals are concerned that the government has not acted aggressively enough and they want broader control programs initiated. Cormorant-caused damage to private property is also of concern to some landowners in areas where nesting, roosting, and/or loafing occurs. There are some inherent differences of self-interest between a private landowner and the general public when dealing with human-wildlife conflicts (Conover 2002). Private landowners have specific rights under the Fish and Wildlife Conservation Act to deal with cormorants causing property damage (see Section 7.3 Private Land). To better quantify and evaluate the socio-economic impacts of cormorants in Ontario additional information is needed. Section 9.0 Research and Information Needs outlines some of the research and data required to conduct a socio-economic analysis related to cormorants in Ontario.


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6.0 RESEARCH AND MONITORING The Ontario Ministry of Natural Resources has been involved with a number of cormorant-related research and monitoring programs in recent years. These programs have focused on areas that are of particular concern to the government and the public for various ecological, social, and economic reasons. This section of the report presents some background information on some important research and monitoring programs in Ontario. 6.1 LAKE HURON MONITORING AND RESEARCH PROGRAM A multi-year project in Georgian Bay and the North Channel of Lake Huron was designed to assess two important elements in the cormorant-fisheries policy debate. First, determining the scale and magnitude of cormorant fish consumption relative to fish production in the coastal regions of Lake Huron provides information on the possible effects cormorants have on nearshore fish production. Second, experimentally lowering fish consumption through egg oiling during the cormorant nesting period provides information on the possible interrelationship between predator (i.e., cormorants) and prey (i.e., fish). This two-part approach can be posed in relevant questions. What is the magnitude of fish consumption by cormorants and what proportion of annual available fish production does this consumption represent? If fish consumption by cormorants is lowered, do we detect a response in the nearshore fish catch or biomass? The experimental design consisted of four sample frames in the North Channel and three sample frames in Georgian Bay. Each frame was 20 km X 20 km in dimension in which nest counts, density estimation of free-ranging cormorants, and fisheries surveys were conducted. Egg oiling was implemented in some frames at staggered intervals while in other frames no egg oiling took place. These served as reference sites for bird and fish surveys in the absence of egg oiling. A detailed methodology manual of this multi-year research program has been published by OMNR (Ridgway et al. 2006). The results of this study are pending. They are currently being analyzed and peer-reviewed for publishing in the scientific literature.

Photo credit: P. Hubert


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6.2 EAST SISTER ISLAND PROVINCIAL NATURE RESERVE

MONITORING East Sister Island is located in the western basin of Lake Erie, approximately 25 km south of Leamington and 13 km west of Pelee Island. The 15 hectare island and 38 hectares of its surrounding water body was acquired by the Province of Ontario in 1971 and regulated under the Provincial Parks Act in 1976 as a provincial nature reserve (OMNR 2003). Provincial Nature Reserves are defined by earth and life science classifications, and are intended to protect natural features and ecosystems that are not found in the other park classes (i.e. natural environment class, wilderness class, historical class, recreational class, waterway class) (OMNR 1992). East Sister Island Provincial Nature Reserve is located in the Carolinian ecozone and is considered to be characteristic of the pre-settlement flora and fauna of the Erie islands because of minimal human disturbances (OMNR 2003). The combination of the island’s southern location and the moderating effects of the lake result in one of the longest growing seasons in eastern Canada, which makes it of particular ecological importance. East Sister Island supports as many as 173 native plant species, including 22 nationally rare plant species (Kamstra et al. 1995). Various studies on East Sister Island Provincial Nature Reserve have reported the presence of these rare species and species at risk, including the Lake Erie watersnake, Kentucky coffee tree, Short’s aster (Symphyotrichum shortii), and several other animal and plant species not found elsewhere in Canada (Tracey et al. 1971, Kamstra et al. 1995, Crins and Oldham 2000, COSEWIC 2002, Hebert et al. 2005, Koh 2005). Significant vegetation communities identified in this area include the black maple – hackberry forest and hackberry – elm – red ash forest. In the western central part of the island a Kentucky coffee tree stand provides habitat for a large heronry. At present, this heronry represents a major breeding colony for great blue herons and black-crowned night-herons. East Sister Island is considered to be a nationally significant colony for colonial waders, including the above species as well as great egrets (Koh 2005, BirdLife Internationl 2005). Cormorant nests have been counted by the Canadian Wildlife Service on the islands in the western basin of Lake Erie since the late 1970s (Weseloh et al. 1995). In 1981, six cormorant nests were first observed on East Sister Island, which had expanded to a reported 4,690 nests by 2005 (Figure 6.1). In 2005, Canada and the United States coordinated a Great Lakes-wide nesting census that indicated there were 17,420 cormorant nests on Lake Erie (Weseloh et al. 2006).


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0

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1980

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ests

Figure 6.1. Double-crested Cormorant nest counts on East Sister Island from 1980 to 2005. Absent data indicate that no nest counts were conducted that year on East Sister Island. (Source: Canadian Wildlife Service, unpublished data).

Expanding cormorant nesting populations on East Sister Island prompted a number of concerns regarding their impacts on the island’s ecosystem. In 2004, Koh (2005) conducted a study to determine the effects of cormorants on the forest habitat of East Sister Island. The objectives of that study were to:

a) Assess the vegetation damage associated with the expanding colony of cormorants.

b) Gather baseline data on forest structure and composition. c) To either develop a preliminary cormorant carrying capacity model for East

Sister Island or identify the information gaps required to produce a cormorant carrying capacity model for East Sister Island.

The increase in the number of nesting cormorants over the past decade has led to a corresponding increase in the damage and subsequent death of trees (Koh 2005). Koh (2005) reported 15% tree mortality on East Sister Island, as well as a 50% tree crown dieback in the upper canopy and 51% branch damage in living trees. Koh (2005) noted that these findings were consistent with previous research using infrared photography that showed that canopy openings had become significantly greater between 2001 and 2003 on East Sister Island (Hebert et al. 2005). The result has been an overall simplification of forest structure, which has led to changes in the plant community and a reduction in


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biodiversity. Hebert et al. (2005) reported mortality of the nationally threatened Kentucky coffee tree on East Sister Island. Crins and Oldham (2000) also reported increased mortality of Kentucky coffee trees and the absence of a number of other rare species that were previously found on the western Lake Erie islands before cormorant nesting colonies were established. Based on this research, cormorants are believed to be the main cause of ecosystem changes on East Sister Island (Hebert et al. 2005, Koh 2005). In 2005, research continued on East Sister Island in order to fill information gaps required to develop a cormorant carrying capacity model. Research will lead to the development of a detailed assessment of forest habitat to provide both short and long-term growth trajectories for the forest ecosystem. When available, this information will provide direction to guide future management decisions on East Sister Island. Ontario Parks is currently in the process of preparing the management plan for East Sister Island Provincial Nature Reserve. The management plan will define park goals, objectives and long-term direction for the protection and management of the nature reserve (OMNR 2003). Issues such as cormorant management and restoration of the island's significant vegetation communities will be addressed in the planning process. Public consultation will continue to play a significant role in the development of this management plan (OMNR 2003). 6.3 TOMMY THOMPSON PARK MONITORING The Leslie Street Spit (i.e., Tommy Thompson Park) is a 5 km2 human-made peninsula extending into Lake Ontario at the foot of Leslie Street on the City of Toronto waterfront. The Toronto and Region Conservation Authority (TRCA) owns and manages approximately half this land base formally known as Tommy Thompson Park. Construction of this site began in 1959 and continues today through the placement of clean fill and dredged sand and silt from the mouth of the Don River. Over time a variety of habitats have evolved at the park, which have attracted significant numbers and species of birds and other wildlife. The site provides habitat for significant waterbird colonies, including ring-billed gulls (Larus delawarensis), herring gulls, common terns (Sterna hirundo), Caspian terns (Sterna caspia), black-crowned night-herons, and the double-crested cormorants. During some years, as much as 30% of Canada’s black-crowned night-heron population breed at Tommy Thompson Park (BirdLife International 2000). The presence of these significant colonies contributed to the site being identified as an Environmentally Significant Area (TRCA 1989, TRCA 1992). In 2000, Tommy Thompson Park was designated as a Globally Significant Important Bird Area, indicating that the protection of this site is necessary to ensure the long-term conservation of naturally occurring bird populations (BirdLife International 2000). Cormorants began colonizing Tommy Thompson Park in 1990, when 6 nests were built in cottonwood trees at the end of Peninsula B (Figure 6.2). Since 1990, the TRCA has


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conducted nest monitoring for cormorants and other colonial nesting birds in the park. During the period from 1990-2000, the nesting distribution of cormorants expanded to cottonwood trees on Peninsulas A, B and C (Figure 6.2). From 2000 to 2005, cormorant nest counts increased by approximately 78%, from 3,187 to 5,674 nests (TRCA unpublished data).

Figure 6.2. Tommy Thompson Park Peninsulas A, B, C, and D. (photo from TRCA) Black-crowned night-herons established a colony in Tommy Thompson Park around 1979 with 7 nests observed. By 2000, the size of the colony had grown to 1,243 nests and has fluctuated around 1,000 nests since then. This colony of black-crowned night-herons is the largest in the Great Lakes. The significance of this colony was also partly responsible for the site being designated as a Globally Significant Important Bird Area (BirdLife International 2000). Increased damage and destruction of tree vegetation has been evident as cormorant colonies expand in Tommy Thompson Park. Cormorants have recently expanded their colony into the area where the black-crowned night-herons are nesting (Jarvie et al. 1999). There is concern that the black-crowned night-heron colony will be displaced and/or adversely affected by the expanding cormorant colony. The TRCA has conducted a variety of colonial waterbird management activities in Tommy Thompson Park since the early 1980s. In 2001, management efforts focused on harassment and deterrent techniques in an attempt to limit the expansion of cormorant colonies into nesting habitat used by black-crowned night-herons. Harassment and deterrent techniques have included nest removal prior to nesting and disturbance of cormorants around Peninsula C using noise bangers and laser lights. These methods have proved to be largely ineffective at reducing the number of nesting cormorants and habitat destruction on Peninsula C.


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The TRCA is currently developing management strategies to reduce the number of cormorants around Peninsula C. Future TRCA management strategies may include egg oiling in addition to nest removal and harassment techniques. The Ministry of Natural Resources has been providing direction and guidance on legislative provisions (Protection of Property Provisions) under the Fish and Wildlife Conservation Act. 6.4 PRESQU’ILE PROVINCIAL PARK CORMORANT MANAGEMENT

STRATEGY The Management Plan for Presqu’ile Provincial Park was completed in 2000 (OMNR 2000). The Presqu’ile Management Strategy for Double-crested Cormorants was completed in 2002 (OMNR 2002). The management strategy allowed for the oiling of eggs in ground nests, the removal of nests from trees, and the harassment of cormorants roosting in trees on High Bluff Island. In 2003, an amendment to the cormorant management strategy included oiling eggs in ground nests on Gull Island. Another amendment in 2004 allowed the removal of tree nests and the culling of tree nesting cormorants on High Bluff Island (OMNR 2004b). Goal and Objectives The goal of the Presqu’ile Provincial Park Cormorant Management Strategy is:

- to protect representative woodland flora and fauna of Gull and High Bluff Islands, Presqu’ile Provincial Park, while retaining maximum diversity of nesting colonial bird species.

The four objectives associated with this goal are:

- to limit cormorant use of trees for nesting on High Bluff Island, - to reduce cormorant use of trees for roosting on High Bluff Island, - to reduce recruitment from ground nests of cormorants on Gull and High Bluff

Islands, - to minimize the impacts of cormorant management on other colonial bird species

nesting on Gull and High Bluff Islands. Management Activities Ontario Parks has employed oiling of eggs in ground nests and the removal of tree nests to limit breeding and recruitment into the population. Culling of adult tree nesting cormorants has also occurred, which aids in reducing population size and also limits population recruitment (Table 6.1). These management activities also reduce physical damage associated with nest construction and chemical damage as a result of the deposition of guano. Disturbance of roosting cormorants during the post-breeding season has also been conducted to reduce chemical damage to vegetation.


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Artificial ground nesting sites were created on High Bluff Island in an attempt to encourage cormorants to nest on the ground rather than in trees. These sites have had variable success. Ontario Parks staff have attempted site rehabilitation on High Bluff Island through tree planting (Table 6.1). Monitoring Activities Monitoring various activities and species has been conducted from May to September since the Presqu’ile Provincial Park Cormorant Management Strategy was implemented in 2002. Cormorant nests are counted in early-mid June of each year (Table 6.1). The majority of culled cormorants are composted on High Bluff Island. Biological data are collected from some culled cormorants (e.g., weight, sex, banding data) and a number of culled cormorants are used for other studies (e.g., viral analysis, serology testing, stomach content analysis).

Table 6.1 Summary of information regarding cormorant management activities conducted at Presqu’ile Provincial Park, 2002-2005 (OMNR 2004a, 2005b).

Year Activity 2002 2003 2004 2005

Eggs Oiled 0 28,648 26,311 23,732

Nests Oiled 0 4065 3284 2633

Nests Removed 0 3,980 2,098 1,861

Adults Culled 0 0 6,030 1,867

Trees Planted 0 0 40 600

Tree Nest Count 6,893 4,631 3,656 1,976

Total Ground Nest Count 5,189 4,065 3,284 2,633

Total Nest Count 12,082 8,696 6,940 4,609

Monitoring in 2004 and 2005 involved investigating the nesting success of great blue herons and great egrets. Interactions between cormorants, great blue herons, great egrets, and black-crowned night-herons were monitored during 2004 and 2005. Consideration was given to gathering the best information available, while not compromising the nesting success of any of these heron species during monitoring activities (Table 6.2). As such, all great blue heron nests were surveyed twice monthly, while a sub-sample of 25 nests was monitored more intensively on a weekly basis. The small number of great egret nests facilitated routine monitoring of all egret nests. Black-crowned night-herons are secretive and sensitive to disturbance. For those reasons, black-crowned night-heron nests were only counted twice, and no effort was made to determine actual nesting success.


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Table 6.2 Nest counts and nesting success for a) great blue heron, b) great egret and c) black-crowned night-herons on High Bluff Island, 2003 – 2005 (OMNR 2004a, OMNR 2005b).

a) Great Blue Heron

Year Nest Count

# of Successful

Nests

# of Fledged Young

# of Fledged/Nests

2003 38 25 37 1.48

2004 63 38 75 1.97

2005 42 32 75 2.34

b) Great Egret

Year Nest Count

# of Successful

Nests

# of Fledged Young

# of Fledged/Nests

2003 5 4 10 2.50

2004 10 10 26 2.60

2005 17 16 42 2.63

c) Black-crowned Night-Heron

Year Nest Count

# of Successful

Nests

# of Fledged Young

# of Fledged/Nests

2003 80 unknown unknown unknown



In 2005, the behavioural response of great blue herons and great egrets to culling and nest removal activities at Presqu’ile Provincial Park was monitored and compared to observations at Chantry Island, a control site in Lake Huron (Moore et al. 2005). Moore et al. (2005) indicated that the effects of cormorant culling and nest removal activities on these heron species were minimal, short-term and localized. The herbaceous and woody vegetation on High Bluff Island was surveyed in 2000, 2002 and 2004. The western woodlot was the focus of the studies in 2000 and 2004, with the eastern woodlot added in 2004. These studies have documented a continual decline in the condition of woody vegetation. Herbaceous vegetation has been increasingly dominated by invasive native and non-native plant species.


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6.5 DISEASE MONITORING Episodes of mortality involving double-crested cormorants have been reported to the Canadian Cooperative Wildlife Health Centre (CCWHC) at the University of Guelph since 1992. Post-mortem examinations have been conducted on dead cormorants associated with these reported mortality events to determine the cause of death and to monitor disease occurrence. The two most common diseases of cormorants in Ontario are Avian Paramyxovirus-1 (PMV-1, also known as Newcastle Disease Virus when virulent) and Type E botulism. Newcastle disease (PMV-1) is a deadly and contagious avian disease caused by a virus which affects the nervous system in birds (Kuiken et al. 1998, 1999, Clavijo 2001). Young birds are particularly susceptible to the disease at about 4-5 weeks of age, when their maternal immunity is wearing off. Newcastle disease was first recognized in Ontario cormorants in 1992 when an epizootic of the disease occurred in birds in locations ranging from northern Alberta to the St. Lawrence River (Glaser et al. 1999). Since 1992, PMV-1 has been diagnosed a number of times and at various locations throughout the Great Lakes, but has never re-occurred as a large scale epizootic as it did in 1992. A recent survey of cormorants from Lake Ontario found no Newcastle disease or Avian Influenza virus from over 400 adult cormorants (CCWHC 2005). Type E botulism has been the cause of large scale die-offs involving a variety of species of wild birds on the lower Great Lakes since 1998 (CCWHC 2005). The disease was first diagnosed on Lake Huron and subsequently spread to Lake Erie in 2000 and eventually to Lake Ontario in 2004. Outbreaks during July and August involving cormorants and other waterbirds have tended to be sporadic and localized. However, in August and September of 2004, more than 1,000 cormorants died of Type E botulism in eastern Lake Ontario (CCWHC 2005, Shutt et al. 2005). Most large scale die-offs seen with this disease typically occur in late autumn, when large numbers of fish and mussel-eating birds congregate on the lower Great Lakes. Other conditions, such as parasites affecting the upper digestive tract (Contracaecum spiculigerum), the liver (Amphimerus elongatus) and kidney (Eimeria sp.) are commonly identified in cormorants during post-mortem examinations, but are usually not considered to be the cause of death (Yabsley et al. 2002, CCWHC 2005). 6.6 GREAT LAKES MONITORING Population and Nesting Surveys The Canadian Wildlife Service has been monitoring cormorant populations in conjunction with other provincial and state agencies on the Great Lakes since 1979. A cooperative cormorant population census is conducted annually in the lower Great Lakes


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(including Lake Huron in most years) involving Ontario, Canadian federal, municipal, U.S. state, and non-governmental agencies. This information is used to monitor trends in cormorant population growth and decline over time. The Canadian Wildlife Service and the U.S. Fish and Wildlife Service also coordinate the Great Lakes Bi-national Colonial Waterbird Inventory every ~10 years. This is a comprehensive Great Lakes-wide population survey of all colonial nesting birds, including cormorants (Blokpoel 1977, Blokpoel and Tessier 1996, 1997, 1998, Scharf and Shugart 1998). The last colonial bird survey was conducted from 1997 – 1999 (Cuthbert et al. 2001, Weseloh et al. 2003). In 2005, Canadian and U.S. wildlife officials agreed to conduct a Great Lakes-wide cormorant count to update the existing population census for the bird. As a result, the size and distribution of the cormorant population on the Great Lakes is well known (Weseloh et al. 2006). Contaminants Monitoring and Research The Canadian Wildlife Service and the U.S. Fish and Wildlife Service have been monitoring contaminant levels in cormorants and other Great Lakes waterbirds since the mid-1970s (Weseloh et al. 2003). This contaminant monitoring is ongoing as part of the Great Lakes Binational Colonial Waterbird Inventory and the Herring Gull Egg Contaminants Monitoring Program. Numerous scientific studies have investigated changing contaminant levels in the Great Lakes and their effects on gulls, cormorants, and other colonial waterbirds (Weseloh et al. 1983, Ewins et al. 1992, Pettit et al. 1994, Weseloh et al. 1995b, Pekarik et al. 1998, Ryckman et al. 1998, DiMaio et al. 1999, Weseloh et al. 2003). The results indicate that there have been major declines in contaminant levels in the eggs of fish-eating waterbird eggs across the Great Lakes, which have contributed to healthier waterbird populations over the past 20 years (Weseloh et al. 2003). 6.7 INLAND LAKE MONITORING Ontario Ministry of Natural Resources (OMNR) Districts, Provincial Parks, and Fisheries Assessment Units have participated in formal and informal monitoring projects on inland lakes since the late 1970s. Periodic province-wide OMNR surveys have been conducted to synthesize this monitoring information and assess cormorant movement patterns on inland lakes. A provincial survey completed in 1996 determined that some inland lakes had increasing numbers of non-breeding cormorants (i.e., using the lakes for feeding and loafing). Inland cormorant colonies were generally found to be smaller than Great Lakes colonies due to reduced food supply and suitable nesting habitat on inland lakes (OMNR 1997, Rowe 2003).


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In 2005, OMNR conducted a province-wide survey to update the inland lake cormorant information obtained in 1996. This updated information is presented in Section 4.2 Inland Lakes. From 1981 – 1985, the Federation of Ontario Naturalists and the Long Point Bird Observatory coordinated a province-wide breeding bird survey and the development of the Ontario Breeding Bird Atlas (Cadman et al. 1987). Many government and non-government agencies, including Bird Studies Canada, Canadian Wildlife Service, Ontario Field Ornithologists, Federation of Ontario Naturalists, Ministry of Natural Resources, and volunteers provided funding and participated in this comprehensive program. The Ontario Breeding Bird Atlas is currently being updated from another extensive series of provincial surveys that took place from 2001 – 2005 (OBBA 2005), and is expected to be published in the fall of 2007. 6.8 ALGONQUIN PROVINCIAL PARK MONITORING Algonquin Provincial Park, established in 1893, is one of the oldest, largest, and most visited protected areas in Ontario. It lies in the transition zone between southern deciduous forests and northern coniferous forests. The first objective of the Algonquin Park Management Plan is “to protect provincially significant elements of the natural and cultural landscape of Algonquin Park” (OMNR 1998). One of the most significant features in Algonquin Park is the presence of self-sustaining, genetically unique brook trout populations. The Park contains the greatest concentration of self-sustaining brook trout lakes in the world and approximately 25% of Ontario’s self-sustaining brook trout lakes (Mandrak and Crossman 2003). The Park has many ongoing research and monitoring programs directed at protecting the Parks ecological integrity with emphasis on species interactions. In particular, cormorants are being monitored because of their potential impacts on local fisheries, vegetation, and other colonial bird species. McIntyre (1955) observed the first recorded cormorant in Algonquin Park in 1954. Historical Algonquin Park Museum records show no evidence of cormorants in the park prior to 1954 (OMNR 2005c). The Algonquin Park Museum records are based on historical reporting by Park Rangers, Superintendents and Park Naturalists. During the 1970s and 1980s cormorants were observed sporadically by park staff and visitors, and by 1991 cormorants were being observed every year in the park (OMNR 2005c). In 2002, cormorant nesting was first recorded in Algonquin Park with four nests observed on Gull Island in Lake Opeongo and one nest was observed on Merchant Lake (OMNR 2005c). In 2005, there were 59 cormorant nests recorded in Algonquin Park with 57 on Lake Opeongo and 2 on Kioshkokwi Lake (OMNR 2005c) (Figure 6.3). Cormorants are now regularly observed in many areas of the Park (OMNR 2005c).


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Figure 6.3 Nest counts for Double-crested Cormorants on Lake Opeongo in Algonquin Provincial Park, 2002 – 2005.

In 2005, aerial waterbird surveys were conducted on 18 medium – large lakes (including Lake Opeongo) to assess early summer, late summer and fall cormorant populations throughout Algonquin Park. While more than 100 cormorants were observed loafing and foraging on some lakes, none were observed on other lakes. The aerial surveys showed that Lake Opeongo, Dickson and Kioshkokwi had resident cormorant populations throughout the summer. Annual aerial waterbird surveys will continue to monitor cormorant populations in Algonquin Park. During 2005, Ontario Parks also conducted a Geographic Information System habitat study for cormorants in Algonquin Park. Lakes with desirable characteristics for cormorant nesting (i.e., size >20 hectares, presence of islands, presence of heronries or gull rookeries, etc.) were examined for their potential to support a cormorant nesting colony (Goodwin and Rosche 1972, Hatch and Weseloh 1999, Sandilands 2005). Of the 2,456 lakes in Algonquin Park, 313 are of sufficient size and contain nesting characteristics suitable for a cormorant colony. Thirty of the lakes examined also possess heronries or gull rookeries. Monitoring of cormorant roosting and nesting sites will continue in Algonquin Park. Ontario Parks intends to develop a research and monitoring plan with the particular objective of determining whether cormorants are having an impact on lakes containing natural and self-sustaining populations of brook trout (Quinn et al. 1994, Vascotto 2004).


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7.0 ONTARIO LEGISLATION and CURRENT PROVINCIAL POLICY Double-crested cormorants are not included under the federal Migratory Birds Convention Act, and thus are not protected by federal law. Cormorants are protected under Ontario’s Fish and Wildlife Conservation Act 1997 (FWCA), which prohibits the hunting and trapping of cormorants. The FWCA also prohibits the destruction, taking and/or possession of nests or eggs without authorization from the Minister of Natural Resources. The current provincial policy for cormorant management is based on the status report document: “Review of the Population Status and Management of Double-crested Cormorants in Ontario” (OMNR 1997). The draft policy was posted on the Environmental Bill of Rights (EBR) registry for public comment in 1997 and was approved for implementation in 1998. It established the current guiding policy direction:

“that the control of cormorant numbers should only be considered in specific local areas if the birds are found to be having significant negative, ecological impacts on habitats or other species”.

This guiding policy direction leads to the application of a site-by-site approach for cormorant management on both Crown and private lands. It directs the OMNR to confirm reasonable evidence of significant negative effects on natural resource values at the target site prior to undertaking control activities. Control activities are to be accompanied by public consultation, monitoring and reporting. The FWCA provides specific provisions which allow private landowners the ability to protect their property from wildlife. There are a number of conditions and legal requirements that must be followed when harassing or killing wildlife for the protection of property (for more details see Section 7.3 Private Land). 7.1 OMNR ROLES and RESPONSIBILITIES OMNR is responsible for managing cormorants in Ontario. The FWCA provides the legal basis for this management, and policy direction has been developed for activities related to research, protection of other species, or the protection of habitats. Natural resource management responsibilities for the OMNR are primarily focused on Crown lands; however its responsibility under the FWCA extends to wildlife species that occupy both Crown and private lands. OMNR is committed to ensuring the long-term health of ecosystems and the protection of biodiversity in Ontario. This involves maintaining a diversity of habitat for all species that are wild by nature.


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OMNR has been leading a provincial inter-ministerial steering committee and public stakeholders in drafting a strategy for addressing human-wildlife conflicts in Ontario. The proposed strategy provides a policy umbrella under which human-wildlife conflict prevention can be addressed. It describes the current nature of human-wildlife conflicts, current policy and programs, the associated challenges for Ontarians, and suggests key objectives and strategies for preventing and managing human-wildlife conflicts in Ontario. The province’s commitment to help Ontarians prevent and manage human-wildlife conflicts is highlighted in Our Sustainable Future (OMNR 2005d) and Ontario’s Biodiversity Strategy (OMNR 2005e). Both documents emphasize the importance of promoting conservation of natural resources and maintaining biodiversity, while protecting human health and safety and fostering economic growth in Ontario. Future cormorant management decisions will be determined based on these guiding policy documents, the best available science, and will involve public consultation. 7.2 CROWN LAND Breeding and roosting sites of cormorants on Crown lands are protected under the FWCA. It is illegal to hunt or trap cormorants on Crown lands (and waters) or to destroy, take, or possess their nests or eggs without authorization from the Minister of Natural Resources. In specific circumstances, OMNR may undertake management and monitoring programs involving the harassment and/or killing of cormorants on Crown lands for the purpose of deterring or preventing the birds from causing significant negative ecological damage to habitats or other species (e.g., Presqu’ile Provincial Park). 7.3 PRIVATE LAND The FWCA has specific provisions which enable private landowners to protect their property from cormorants. Under Subsection 31(1) an individual who believes on reasonable grounds that cormorants are damaging or are about to damage their property may harass, capture or kill the cormorants on their property. More than the mere presence of cormorants is required for the protection of property provisions to apply. The onus is on the private landowner to provide proof of “reasonable grounds” under Subsection 31(1) of the FWCA. The destruction of trees and vegetation on private property or depredation of fish from a privately owned aquaculture facility may constitute reasonable grounds to harass, capture or kill cormorants. Under Subsection 7(1) of the FWCA, a person may not destroy, take or possess the nest or eggs of cormorants on either Crown or private land without authorization from the Minister of Natural Resources.


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Under Subsection 31(2) of the FWCA, the Minister of Natural Resources may authorize a landowner to use an agent on their behalf to harass, capture or kill cormorants on their privately owned land. Section 31 of the FWCA requires that there be no unnecessary suffering to the birds and that control measures be limited to the number of birds that is necessary to protect the property. Dispatch of adult nesting cormorants could deprive hatchlings of sustenance and shelter and cause suffering. Private landowners who choose to exercise their rights to protect private property should only do so at a time and in a manner that will not cause unnecessary suffering. It is the responsibility of the private landowner to ensure that they follow all relevant legal requirements when taking actions under the protection of property provision of the FWCA. For more information, private landowners should contact their local MNR office. 8.0 CORMORANT MANAGEMENT IN OTHER JURISDICTIONS Natural resource management agencies in Canada and the United States were contacted in 2005 to gather information on the status of cormorants, management actions undertaken, and their effectiveness. 8.1 CANADIAN PROVINCES Provincial natural resource agencies are responsible for managing double-crested cormorants in Canada. As discussed in section 7.0 Ontario Legislation and Current Provincial Policy, the federal Migratory Bird Convention Act does not include double-crested cormorants on its species list, and therefore they are only granted protection under provincial legislation. All Canadian provinces provide some level of protection to cormorants under their provincial wildlife legislation. Seven provinces (AL, SK, MB, ON, QC, PEI, NB) reported that cormorant populations were increasing, while only two provinces (NS, NFLD) reported populations as stable. All provinces surveyed indicated that cormorants have been causing conflicts in their province, with the exception of Newfoundland. No Canadian provinces are currently engaged in any large-scale provincial cormorant management or control programs; however there are some on-going regional research programs. The majority of provinces provide specific provisions or permits under their provincial wildlife legislation that permit the taking or harassment of cormorants for the protection of private property or resources (e.g., aquaculture facilities, fish stocking programs, etc.), except in Newfoundland where there are associated conservation concerns with great cormorants (Phalacrocorax carbo). Site-specific controls have had


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variable effectiveness depending on the extent of the local control actions. All provinces reported that site-specific controls have not reduced province-wide cormorant numbers. In New Brunswick, double-crested cormorants can be hunted during the periods prescribed as open season for waterfowl under their provincial Migratory Bird Regulations. In 1996, New Brunswick added double-crested cormorants to their provincial varmint license to give private landowners more flexibility in dealing with increasing cormorant-related conflicts (primarily related to aquaculture activities). Double-crested cormorants can be hunted province-wide under the varmint license from March 1st to Sept 20th, excluding coastal waters in order to prevent persecution to breeding colonies. Very few cormorants have been taken during waterfowl hunts or under the varmint license, and as a result, these management actions have led to no overall impact on the cormorant population in New Brunswick. In 1992, Prince Edward Island included double-crested cormorants in the first two weeks of the waterfowl hunting season to alleviate concerns surrounding cormorant conflicts in the province. The hunting season did not have an impact on the double-crested cormorant population over four years of monitoring, but appeared to have a negative impact on great cormorant populations because it was difficult to discriminate between the two species. As a result, Prince Edward Island removed the double-crested cormorant from the waterfowl hunt in 1997. From 1989 to 1994, Quebec undertook a cormorant management program in the St. Lawrence estuary to reduce the breeding population from approximately 17,000 nests to 10,000 nests (Bedard et al. 1995). The control program involved oiling eggs on ground nesting colonies and culling adults. The program was implemented to help protect the biodiversity of island vegetation in the area; therefore nesting colonies on islands with no vegetation were left alone. During the 5 year program approximately 8,000 cormorants were culled and 26,000 nests were oiled. Overall, the control program reduced the cormorant population and was effective in reducing vegetation damage in the area. However, since 1994 cormorants on the St. Lawrence estuary have rebounded. Quebec has suggested that a similar control program may be required on a continuous basis to be effective in the long-term. Quebec is currently conducting population monitoring and research on the Lake Saint-Pierre portion of the St. Lawrence River as part of a research program on cormorant impacts on local fisheries, particularly on yellow perch. Quebec has been oiling eggs in 50% of the nests (i.e., approximately 450 nests in 2005) at a major colony on Lake Saint-Pierre since 2002 to determine the effectiveness of egg oiling and its impacts on local fish populations. Manitoba is currently not engaged in any provincial cormorant research or monitoring program. Manitoba had a cormorant control program in the 1940s, which was discontinued in 1954 (McLeod and Bondar 1953, Hatch 1995, OMNR 1997). Past population surveys have suggested that Lake Winnipegosis contains the largest breeding population of cormorants in Manitoba (Koonz and Rakowski 1985, OMNR 1997).


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Cormorant and fisheries-related conflicts remain a concern among stakeholders in Manitoba. Saskatchewan is currently conducting research on various cormorant-related topics through the University of Regina and the Canadian Cooperative Wildlife Health Centre. Research topics include diet analysis, disease monitoring, impacts on fisheries, habitat use, natal philopatry, and nesting interactions with other colonial birds. In 2003, Alberta initiated a 5-year cormorant management project in the Lac La Biche area as part of a provincial fish recovery initiative under their Fisheries Amendment Act. The cormorant management project has been studying the impact of cormorants on Alberta’s environment, including their possible influence on sport and commercial fisheries. Approximately 2,900 nests were oiled in 2003 and up to 75% of cormorant eggs were oiled in selected colonies in the Lac La Biche area. Approximately 4,500 nests were oiled in 2005 as part of the cormorant management project. Alberta also initiated a culling program for the first time in the Lac La Biche area in 2005, where approximately 1,000 cormorants were taken. 8.2 UNITED STATES OF AMERICA Background The U.S. Fish and Wildlife Service (USFWS) is responsible for managing migratory birds in the United States under the Migratory Bird Treaty Act (MBTA). Cormorants are listed as a migratory bird under a 1972 amendment to the convention between the United States and Mexico. As such, the double-crested cormorant is federally protected under the MBTA in the United States, and the take of cormorants is prohibited except as authorized by the regulations of the MBTA. The Migratory Birds Convention Act between the United States and Canada does not list double-crested cormorants as a migratory bird. Although cormorants are protected under the Migratory Bird Treaty Act, lethal means of control are permitted by the USFWS in order to allow for the alleviation of conflicts between cormorants and other resources, such as aquaculture stock, property, or natural resources. Depredation permits are generally issued to an agency (e.g., USDA APHIS Wildlife Services) or to a private individual (e.g., aquaculture operator). . Increasing cormorant populations have caused biological and socio-economic resource conflicts in the United States, and as a result, the USFWS completed a federal Environmental Impact Statement (EIS) in 2003 to address the impacts caused by population and range expansion of cormorants. After public consultation and review, the USFWS approved recommendations in the EIS for two standing Depredation Orders. The first allowed State fish and wildlife agencies, Native American tribes, and the Wildlife Services program of the U.S. Department of Agriculture Animal and Plant Health Inspection Service (USDA-APHIS) to take cormorants without a permit in order to


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protect public resources. The second authorized aquaculture producers and USDA-APHIS-Wildlife Services to take cormorants to protect aquaculture. The EIS examined numerous management alternatives for addressing conflicts with cormorants, from no action to regional population control, but ultimately determined that a standing Depredation Order would be the most effective option in enhancing the ability of resource agencies to deal with immediate, localized cormorant damages by giving them more management flexibility. In December 2003, the USFWS implemented the Depredation Orders, both of which expire on April 30, 2009. The two types of depredation orders are as follows:

1) Public Resource Depredation Order The purpose of the Public Resource Depredation Order was to reduce the occurrence and/or minimize the risk of adverse impacts to public resources (i.e., fish, wildlife, plants and their habitats). Under this order, designated agencies are not required to obtain a permit/approval from the USFWS to implement cormorant control measures (i.e., oil eggs, remove nests, kill or harass cormorants) to prevent depredations of public resources such as, fish, wildlife, plants, or their habitats. However, the USFWS must approve any control activity that will kill >10% of the breeding colony. This Public Resource Depredation Order was granted to 24 States, including AL, AR, FL, GA, IA, IL, IN, KS, KY, LA, MI, MN, MO, MS, NC, NY, OH, OK, SC, TN, TX, VT, WI, and WV. The remaining States still require a permit from the USFWS under this order. The Public Resource Depredation Order does not authorize the taking of cormorants by the general public and does not authorize any state/federal agency or aboriginal tribe to conduct regional cormorant population reduction efforts. Approximately 2,300 cormorants were taken under the Public Resource Depredation Order in its first year of activity (i.e., 2004) (USFWS unpublished summary).

2) Aquaculture Depredation Order

The purpose of the Aquaculture Depredation Order is to reduce depredation of aquaculture stock at freshwater commercial aquaculture facilities and State/Federal fish hatcheries. This order applies to both private and government aquaculture facilities. Under this order, no permit is required by designated agencies to kill cormorants on facility property or at roosting sites (with landowner permission). The Aquaculture Depredation Order was granted to 13 States including AL, AR, FL, GA, KY, LA, MN, MS, NC, OK, SC, TN, and TX. The remaining States require a permit from the USFWS under this order. In 2004, approximately 23,400 cormorants were taken under the Aquaculture Depredation Order (primarily in the southern United States) (USFWS unpublished summary).

The USFWS predicted that <160,000 cormorants will be taken under these orders during its operation. General conditions apply to both types of Depredation Orders, such as


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annual reporting to the USFWS of the number of cormorants taken and a requirement that non-lethal controls be used when they are considered effective, practicable, and not harmful to other nesting birds. Private landowners may obtain permits to take cormorants from the USFWS if they are causing damage to private resources or property. In 2004, the USFWS reported that five out of 24 eligible states utilized the Public Resource Depredation Order (PRDO) in the United States, including Arkansas, Georgia, Michigan, New York, and Vermont. Approximately 2,300 cormorants were taken and 16,000 cormorant nests were oiled or removed under the PRDO in 2004 (first year of PRDO implementation) (USFWS unpublished summary). Although efforts to date have been focused on a local scale, the USFWS has said that a broader and more coordinated approach will likely need to be considered over the long-term in order to address growing cormorant populations. If supported by biological evidence and appropriate monitoring resources, the USFWS has suggested that it may authorize a management approach that focuses on setting and achieving regional population goals in the future. The development of a U.S. wide cormorant management plan would occur at that time; however until then the USFWS will focus on mitigating and alleviating localized damage. U.S. Cormorant Management in 2005 The OMNR jurisdictional scan of the United States cormorant-related activities yielded 22 responses from the Mississippi and Atlantic flyways. Seventeen states (MN, WI, MI, OH, AL, AR, KY, MS, IA, IN, PA, VT, CT, NJ, MD, FL, TX) reported that cormorant populations are increasing, while only 5 states (NC, RI, ME, WV, NY via management) reported that populations were stable. Sixteen states (MN, WI, MI, OH, AL, AR, KY, MS, IA, PA, NY, VT, ME, CT, FL, TX) indicated that cormorants are causing conflicts in their state. In 2005, seven out of 24 eligible states utilized the Public Resource Depredation Order (PDRO) in the United States, including Alabama, Arkansas, Michigan, Minnesota, New York, Texas, and Vermont. Approximately 11,700 cormorants were taken and 17,300 cormorant nests were oiled or removed under the PRDO in 2005 (USFWS unpublished summary). The majority of this management activity occurred in the four Great Lakes region states, with approximately 8,000 cormorants taken and 17,300 cormorant nests oiled or removed (USFWS unpublished summary) (Figure 8.1). New York and Michigan have the most intensive management programs, which combine nest removal or egg oiling with taking adult cormorants at various locations. These programs have been reported to be the most effective in reducing cormorant numbers and their associated impacts on fisheries, vegetation, and other wildlife (Farquhar et al. 2003, USFWS 2003). Ohio will be initiating cormorant management activities under the PRDO for the first time in 2006.


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Figure 8.1 Map of the Great Lakes region jurisdictional boundaries and United States cormorant management activities under the Public Resource Depredation Order in 2005. 9.0 RESEARCH AND INFORMATION NEEDS There will always be gaps in our knowledge of double-crested cormorant biology, behaviour, and population dynamics in a changing environment. Cormorant impacts on various resources in a variety of ecological settings will continue to evolve in the face of conflicts with human socio-economic values. As such, various research and information needs have been put forward in the scientific literature and in symposium summaries over the last 10 years (Erwin 1995, Nisbet 1995, Carss 1997, Hatch and Weseloh 1999, Weseloh and Lewis 1999, Wires et al. 2001). The OMNR should continue working with other groups, agencies and jurisdictions to conduct monitoring and research on cormorant populations and their effects on fisheries, vegetation, and other species. This information is essential in determining if management action is necessary, and if so, the type and scale of management action that is both appropriate and effective.

Issued Public Resource Depredation Order(s) in 2005

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Status on the Great Lakes Cormorant colony and nest counts are critical in monitoring population trends over time (as discussed in section 4.1 Great Lakes and section 6.6 Great Lakes Monitoring). The OMNR has managed or participated in the following, and should continue to do so in the future:

▪ conduct annual cormorant nest counts on Georgian Bay, the North Channel, and the main body of Lake Huron,

▪ participate in the annual cooperative cormorant population census on Lake Ontario, Lake Erie, and the St. Lawrence River involving the Canadian Wildlife Service and U.S. State Fish and Wildlife agencies and support/participate in special initiatives to census Great Lakes-wide cormorant nesting,

▪ support and participate in the decadal Great Lakes Bi-national Colonial Waterbird Inventory with the Canadian Wildlife Service and the U.S. Fish and Wildlife Service.

Status on Inland Lakes There is a need to better assess the status of cormorant nesting on Ontario’s inland lakes. As described in Section 4.2 Inland Lakes, much of this information is anecdotal and does not allow for evaluation of population trends. As such, there is a need to:

▪ establish an annual inland lake cormorant nest monitoring network to obtain more complete and consistent information on the status of cormorant nesting populations on inland lakes across Ontario,

▪ consider maintaining an inventory of islands without nesting, but where cormorants roost during the post-breeding season, as these sites may suggest future nesting areas,

▪ consider maintaining an inventory of lakes without nesting to make tracking of newly established colonies easier,

▪ consider developing a habitat suitability model for specific inland regions to help focus inland lake monitoring efforts.

Biology and Management Much cormorant research has been conducted since the provincial “Review of the Population Status and Management of Double-crested Cormorants in Ontario” was completed in 1997. However, there are still a number of biology and management knowledge gaps that need to be addressed, including:

▪ greater demographic information (i.e., age specific survival/mortality, age at first breeding, reproductive output, and colony movements) for use in modeling to help predict population responses to management activities and environmental variables,


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▪ better data on productivity, survivorship, intercolony movements, and the source-sink dynamics of cormorants nesting on the Great Lakes and inland lakes in Ontario,

▪ information on migration patterns, routes, movements, and winter distribution of Great Lakes cormorants. This would involve banding and satellite telemetry on a continental scale.

▪ collaborative continental or flyway-wide cormorant surveys to document broad-scale changes in North American breeding populations,

▪ population genetics (i.e., genetic diversity, gene flow, etc.) data on cormorant populations in the Great Lakes,

▪ studies to determine metabolic rates and daily energy expenditure by cormorants,

▪ studies to determine how cormorant population processes respond to changes in population density as a result of management activities,

▪ studies to determine the effectiveness of management activities (i.e., nest removal, egg oiling, culling) at various scales,

▪ studies to determine if management activities push cormorants into other previously unoccupied areas. This would involve banding and tracking bird movements,

▪ studies to develop new non-lethal methods of population control that minimize conflicts.

The International Association of Fish and Wildlife Agencies (IAFWA) Bird Conservation Committee proposed expanding the flyway system in 2005 (IAFWA 2005). The IAFWA recommended the formation of non-game migratory bird technical sections under the existing Flyway Councils to serve as a forum for addressing non-game bird management issues at the regional and national scales (IAFWA 2005). The OMNR believes this would be an important step in addressing some key information and collaboration needs with respect to cormorant management. Fisheries Several important studies have been conducted since the “Review of the Population Status and Management of Double-crested Cormorants in Ontario” was completed in 1997 that have shed light on cormorant impacts on fisheries (as discussed in section 5.1 Impacts on Fish). Recent fisheries and ornithological research has shown that the interactions between cormorants and fish are complex and dynamic in the Great Lakes basin, and impacts can vary greatly. Despite a wealth of research to date, many unknowns remain. Additional research could address some of the following:

▪ the relative effects of cormorants, other environmental factors, and humans on fish populations at varying scales,

▪ studies to examine the mechanisms within fish populations that may buffer the effects of cormorant predation, including further investigations of whether different fish life-stages or species complexes are differentially affected by


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cormorants and whether mortality from cormorant depredation is compensatory, etc.,

▪ assessments of cormorant-caused fish mortality in relation to other mortality factors at varying scales of analysis,

▪ more detailed bioenergetics studies on the Great Lakes and inland lakes to fully understand the dynamics between fisheries and cormorants, including Great Lake specific daily fish consumption rates during breeding and non-breeding periods,

▪ food habits and diet composition of cormorants in western Lake Erie and Lake Huron,

▪ modelling of lake ecosystems to evaluate the consequences of different management scenarios.

Vegetation, Habitat and other Species Cormorant-related impacts on vegetation, habitats, and other species has received more attention in the scientific literature in recent years. Some of these impacts have been summarized in section 5.2 Impacts on Vegetation and section 5.3 Impacts on other Species. Although some impacts have been clearly documented, further research is still needed to fill knowledge gaps, including:

▪ more documentation on the effects of cormorants on vegetation, especially listed species and species at risk,

▪ better information on how cormorant nesting activities may be acting singly and in concert to adversely affect tree health,

▪ further studies to quantify the impacts of cormorants on other waterbirds, particularly during nesting periods,

▪ impacts of cormorant nesting colonies on other terrestrial species, especially listed species and species at risk,

▪ recovery of woody vegetation once cormorant impacts have been reduced, ▪ habitat suitability modeling to predict potential cormorant nesting sites, ▪ the influence of different tree species and substrate type on the rate of tree

decline and mortality at nesting locations.

Socio-economics The human dimensions of cormorant-related conflicts are difficult to assess and have rarely been addressed in the past. It would be beneficial from a management perspective to quantify economic and social impacts in Ontario. Socio-economic analyses may point to possible management solutions through education and outreach in some areas. Socio-economic analyses can be completed at various scales, provided the data and information are specific to the scale of desired analysis. Ideally, a socio-economic analysis would be carried out to assess the socio-economic impact on local citizens that live, cottage, rent, operate a business, etc, in close proximity to a cormorant nesting area.


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Conducting a few small studies of this nature would provide significant insight into the impacts that citizens are experiencing and would provide information to use in valuation studies. In order to complete a social and economic analysis of cormorant impacts in Ontario, information needs include (some of this information may be available through various sources):

▪ cormorant populations (i.e., number of immature, mature, nesting pairs, density), ▪ estimates of fish consumption by the cormorant population, ▪ cormorant migration routes and nesting/foraging/wintering ranges, ▪ movement patterns and range of cormorants in Ontario, ▪ number and location of aquaculture facilities and their level of fish production, ▪ trends and history of recreational boating trips in the area, ▪ trends and history of charter boats trips in the area, ▪ trends and history of angler expenditures in the area, ▪ the number of cottagers, homeowners, camps, motel/hotel facilities in the area, ▪ visitation rates and expenditures for visitors in the area.


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10.0 REFERENCES Aderman, A. R. and E. P. Hill. 1995. Locations and numbers of double-crested cormorants using winter roosts in the delta region of Mississippi. Colonial Waterbirds. 18 (Special Publication 1): 143-151. Alvo, R., Blomme, C., and D.V. Weseloh. 2002. Double-crested cormorants, Phalacrocorax auritus, at inland lakes north of Lake Huron, Ontario. Canadian Field-Naturalist. 116(3): 359-365. Anderson, D. W. and F. Hamerstrom. 1967. The recent status of Wisconsin cormorants. Passenger Pigeon. 29: 3-15. Armstrong, E. R. 1984. Status and trends of the double-crested cormorant population on Lake Abitibi, Ontario. Ontario Ministry of Natural Resources. Unpublished Report. Cochrane, Ontario. Baillie, J. L. 1947. The double-crested cormorant nesting in Ontario. Canadian Field-Naturalist. 61: 119-126. Bédard, J. 1988. Gestion des populations de cormorans à aigrettes dans l’estuaire du Saint-Laurent: resultants de l’étude-pilote et recommandations d’intervention. Rapport soumis à Canards Illimités (Canada). Sauvagîles Ltée., Ste-Foy, Québec, Canada. Bédard, J., Nadeau, A., and M. Lepage. 1995. Double-crested cormorant culling in the St. Lawrence River Estuary. Colonial Waterbirds. 18 (Special Publication 1): 78-85. Belyea, G. Y., Maruca, S. L., Diana, J. S., Schneeberger, P. J., Scott, S. J., Clark, R. D. Jr., Ludwig, J. P., and C. L. Summer. 1999. Impact of double-crested cormorant predation on the yellow perch population of the Les Cheneaux Islands of Michigan. In Symposium on Double-crested Cormorants: Population status and management issues in the Midwest (Tobin, M. E., ed.). United States Department of Agriculture, Animal and Plant Health Inspection Service. Technical Bulletin 1879. Pg. 47-59. December 9, 1997. BirdLife International. 2000. Canadian Important Bird Database. Important Bird Area (IBA) designation for Tommy Thompson Park. Bird Studies Canada and Nature Canada. BirdLife International. 2005. Important Bird Areas of Canada. Canadian Important Bird Area Database. Bird Studies Canada and Nature Canada. Birt, V. L., Birt, T. P., Goulet, D., Cairns, D. K., and W. A. Montevecchi. 1987. Ashmole’s halo: direct evidence for prey depletion by a seabird. Mar. Ecol. Prog. Ser. 40: 205-208. Bishop, R. C. 1987. Economic values defined. In Valuing Wildlife: economic and social perspectives. (Decker, D. J. and G. R. Goff, eds.). Pg. 24-33. Westview Press, Boulder, CO. 424 p. Blackwell, B. F., Krohn, W. B., Dube, N. R., and A. J. Godin. 1997. Spring prey use by double-crested cormorants on the Penobscot River, Maine. Colonial Waterbirds. 20: 77-86.


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Blackwell, B. F., Stapanian, M. A., and D. V. Weseloh. 2002. Dynamics of the double-crested cormorant population on Lake Ontario. Wildlife Society Bulletin. 30(2): 345-353. Blokpoel, H. 1977. Gulls and terns nesting in northern Lake Ontario and the upper St. Lawrence River. Canadian Wildlife Service Progress Note 75. 12 p. Blokpoel, H. and G. D. Tessier. 1996. Atlas of colonial waterbirds nesting on the Canadian Great Lakes. Part 3. Cormorants, gulls and island-nesting terns on the lower Great Lakes system in 1990. Technical Report Series No. 225. Canadian Wildlife Service, Ontario Region. Nepean, Ontario. 74 p. Blokpoel, H., and G. D. Tessier. 1997. Atlas of colonial waterbirds nesting on the Canadian Great Lakes, 1989-1991. Part 2. Cormorants, gulls and island-nesting terns on Lake Huron in 1989. Technical Report Series No. 259. Canadian Wildlife Service, Ontario Region. Nepean, Ontario. 154 p. Blokpoel, H. and G. D. Tessier. 1998. Atlas of colonial waterbirds nesting on the Canadian Great Lakes, 1989-1991. Technical Report Series No. 272. Canadian Wildlife Service, Ontario Region. Nepean, Ontario. 36 p. Britto, D. T. and H. J. Kronzucker. 2002. NH4+ toxicity in higher plants: a critical review. Journal of Plant Physiology. 159: 567-584. Brugger, K. E. 1993. Digestibility of three fish species by double-crested cormorants. Condor. 95: 25-32. Brugger, K. E. 1995. Double-crested cormorants and fisheries in Florida. Colonial Waterbirds. 18 (Special Publication 1): 110-117. Brunson, M. W. 1991. Status of fish farming in the Mississippi. For Fish Farmers. Mississippi Cooperative Extension Service, Mississippi State University, Mississippi State, Mississippi. Bur, M. T., Tinnirello, S. L., Lovell, C. D., and J. T. Tyson. 1999. Diet of the double-crested cormorant in western Lake Erie. In Symposium on Double-crested Cormorants: Population status and management issues in the Midwest (Tobin, M. E., ed.). United States Department of Agriculture, Animal and Plant Health Inspection Service. Technical Bulletin 1879. Pg. 73-86. December 9, 1997. Burnett, J. A. D., Ringler, N. H., Lantry, B. F., and J. H. Johnson. 2002. Double-crested cormorant predation on yellow perch in the eastern basin of Lake Ontario. Journal of Great Lakes Research. 28(2): 202-211. Cadman, M. D., Eagles, P. F. J., and F. M. Helleiner. 1987. Atlas of the Breeding Birds of Ontario. Federation of Ontario Naturalists and the Long Point Bird Observatory. University of Waterloo Press. Pg. 44-45. Waterloo, Ontario. Canadian Cooperative Wildlife Health Centre (CCWHC). 2005. Department of Pathobiology, Ontario Veterinary College, University of Guelph. Guelph, Ontario. Unpublished material.


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Carr, L. W. and S. Koh. 2001. Preliminary assessment of vegetation damage by the common cormorant, northwest forest, High Bluff Island, Presqu’ile Provincial Park. TerraSystems Research. 25 p. Carss, D. N. 1997. Technique for assessing cormorant diet and food intake: towards a consensus view. Supplemento alle Ricerche di Biologia della Selvaggina. 26: 197-230. Chapdelaine, G. and J. Bédard. 1995. Recent changes in the abundance and distribution of double-crested cormorants in the St. Lawrence River, Estuary and Gulf, Québec. 1978–1990. Colonial Waterbirds. 18(Special Publication 1): 70–77. Christie, W. J. 1974. Changes in the fish species composition of the Great Lakes. Journal of the Fisheries Research Board of Canada. 31: 827-854. Christie, W. J., Scott, K. A., Sly, P. G. and R. H. Strus. 1987. Recent changes in the aquatic food web of eastern Lake Ontario. Canadian Journal of Fisheries and Aquatics Sciences. 44 (Supplement 2): 37-52. Clavijo, A., Robinson, Y., and J. Lopez. 2001. Isolation of Newcastle disease virus and Salmonella typhimurium from the brain of double-crested cormorants (Phalacrocorax auritus). Avian Diseases. 45(1): 245-50. Collis, K., Roby, D. D., Craig, D. P., Adamany, S., Adkins, J. Y., and D. E. Lyons. 2002. Colony size and diet composition of piscivorous waterbirds on the Lower Columbia River: Implications for losses of juvenile predation to avian predators. Transactions of the American Fisheries Society. 131: 537-550. Committee on the Status of Endangered Wildlife in Canada (COSEWIC). 1992. Canadian species at risk. Ottawa, Ontario, Canada. Conover, M. 2002. Resolving Human-Wildlife Conflicts: The Science of Wildlife Damage Management. CRC Press LLC: Boca Raton, Florida. 418 p. Core, E. L. 1948. The flora of the Lake Erie Islands. Ohio State University, Franz Theadore Stone Laboratory. Contributions No. 9. Craven, S. R. and E. Lev. 1987. Double-crested cormorants in the Apostle Islands, Wisconsin, USA: population trends, food habits, and fishery depredations. Colonial Waterbirds. 10: 64-71. Crins, W.J, and M.J. Oldham. 2000. Survey of possible double-crested cormorant (Phalacrocorax auritus) impacts on rare plant occurrences on East Sister and Middle Islands, Lake Erie. DRAFT. 7 p. Crowder, L.B. 1986. Ecological and morphological shifts in Lake Michigan fishes: glimpses of the ghost of competition past. Environmental Biology of Fishes. 16: 147-157. Cummings, M. V. 1987. The feeding energetics of the double-crested cormorant in Biscayne Bay, Florida. Ph.D Thesis. University of Miami, Coral Gables, Florida.


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Cuthbert, F. J., McKearnan, J., and A. R. Joshi. 2001. Distribution and abundance of colonial waterbirds in the U.S. Great Lakes: 1997 – 1999. Unpublished report to the U.S. Fish and Wildlife Service. Fort Snelling, Minnesota. Cuthbert, F. J., Wires, L. R., and J. E. McKearnan. 2002. Potential impacts of nesting double-crested cormorants on great blue herons and black-crowned night-herons in the U.S. Great Lakes region. Journal of Great Lakes Research. 28: 145–154. del Hoyo, J., Elliott, A., and J. Sargatal (eds.). 1992. Handbook of the Birds of the World. Vol. 1. Lynx Edicions, Barcelona. Derby, C. E. and J. R. Lovvorn. 1997. Predation of fish by cormorants and pelicans in cold-water river: a field and modeling study. Canadian Journal of Fisheries and Aquatic Science. 54: 1480-1493. DiMaio, J., Pekarik, C. and D. V. Weseloh. 1999. Contaminant levels in herring gull eggs from Lake Erie and the Detroit and Niagara Rivers: change-point regression analysis, 1974 to 1996. In State of Lake Erie – Past, Present and Future. (Munawar, M., Edsall, T. and I. F. Munawar, eds.). Pg. 399-416. Ecovision World Monograph Series, Backhuys Publishers. Leiden, The Netherlands. Dolbeer, R. A. 1990. Double-crested cormorant population status in North America, 1970 – 1989. Denver Wildlife Research Center. Bird Section Research Report. No. 451. Denver, Colorado. Dorr, B., King, D. T., Tobin, M. E., Harrel, J. B. and P. L. Smith. 2004. Double-crested cormorant movements in relation to aquaculture in eastern Mississippi and western Alabama. Waterbirds. 27(2): 147-154. Duffy, D. C. 1995. Why is the double-crested cormorant a problem? Insights from cormorant ecology and human sociology. Colonial Waterbirds. 18 (Special Publication 1): 25-32. Dunn, E. H. 1975. Caloric intake of nesting double-crested cormorants. Auk. 92: 553-565. Dusi, R. T. 1978. Stability of heron colonies in swamp and upland sites. Proceedings of Colonial Waterbirds. 2: 38-40. Eckert, T. H. 1999. Population trends among yellow perch in the eastern basin of Lake Ontario, 1976-98. Section 10:1-25. In Final Report: to Assess the Impact of Double-crested Cormorant Predation on Smallmouth Bass and other fishes of the Eastern Basin of Lake Ontario. NYSDEC Special Report. February 1, 1999. NYSDEC and USGS. 141 p. Edwards, P. A. and T. J. Stewart. 2002. Cormorants in the vicinity of Presqu’ile Provincial Park and the Bay of Qunite. In Lake Ontario Fish Communities and Fisheries: 2001 Annual Report of the Lake Ontario Management Unit. Ontario Ministry of Natural Resources. Picton, Ontario. Ellis, J. C., Farina, J. M. and J. D. Witman. 2006. Nutrient transfer from sea to land: the case of gulls and cormorants in the Gulf of Maine. Journal of Animal Ecology. 75: 565-574.


________________________________________________________________________


Erwin, R. M. 1995. The ecology of cormorants: some research needs and recommendations. Colonial Waterbirds. 18 (Special Publication 1): 240-246. Ewins, P. J. 1994. Aquatic birds in recovering ecosystems – management conflicts. Journal of Great Lakes Research. 20: 597-598. Ewins, P. J., D. V. Weseloh, and P. Mineau. 1992. Geographical distribution of contaminants and productivity measures of herring gulls in the Great Lakes: Lake Huron 1980. Journal of Great Lakes Research. 18(2): 316-330. Fargo, W. G. and J. Van Tyne. 1927. Fall bird notes from the eastern shore of Lake Superior. Canadian Field-Naturalist. 41: 7-9. Farquhar, J. F., Chipman, R. B., Crenshaw, W. J., Slate, D., and J. H. Coleman. 2003. Management of breeding and fall migrating double-crested cormorants in New York and Vermont – eight years of lessons learned. Proceeding of the 10th Wildlife Damage Management Conference. (Fagerstone, K. A. and G. W. Witmer, eds.). Pg. 79 – 86. Glahn, J. F. and K. E. Brugger. 1995. The impact of Double-crested Cormorants on the Mississippi Delta catfish industry: a bioenergetics model. Colonial Waterbirds. 18 (Special Publication 1): 168-175. Glahn, J. F. and A. R. Stickley. 1995. Wintering double-crested cormorants in the delta region of the Mississippi: population levels and their impact on the catfish industry. Colonial Waterbirds. 18 (Special Publication 1): 137-142. Glahn, J. F., and B. S. Dorr. 2002. Captive double-crested cormorant Phalacrocorax auritus predation on channel catfish Ictalurus punctatus fingerlings and its influence on single-batch cropping production. Journal of the World Aquaculture Society. 33: 85-93. Glahn, J. F. and D. T. King. 2004. Bird Depredation. In Biology and culture of channel catfish. (C. S. Tucker and J. A. Hargreaves, eds.). Developments in Aquaculture and Fisheries Science - 34. Elsevier. Amsterdam, The Netherlands. 676p. Glahn, J. F., Dixson, P. J., Littauer, G. A. and R. B. McCoy. 1995. Food habits of double-crested cormorants wintering in the Delta region of Mississippi. Colonial Waterbirds. 18 (Special Publication 1): 158-167. Glahn, J. F., May, A., Bruce, K. and D. Reinhold. 1996. Censusing double-crested cormorants (Phalacrocorax auritus) at their wintering roosts in the delta region of the Mississippi. Colonial Waterbirds. 19: 73-81. Glahn, J. F., Harrel, J. B. and C. Vyles. 1998. The diet of wintering double-crested cormorants feeding at lakes in the southeastern United States. Colonial Waterbirds. 21(3): 446-452. Glahn, J. F., Tobin, M. E., and J. B. Harrel. 1999. Possible effects of catfish exploitation on over-winter body condition of double-crested cormorants. In Symposium on Double-crested Cormorants: Population status and management issues in the Midwest (Tobin, M. E., ed.). United States Department of Agriculture, Animal and Plant Health Inspection Service. Technical Bulletin 1879. Pg. 107-114. December 9, 1997.


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Glanville, E. V. 1992. Co-operative fishing by double-crested cormorants, Phalacrocorax auritus. Canadian Field-Naturalist. 106: 522-523. Glaser, L.C., Barker, I.K., Weseloh, D.V., Ludwig, J., Windingstad, R.M., Key, D.W., and T.K. Bollinger. 1999. The 1992 epizootic of Newcastle disease in double-crested cormorants in North America. Journal of Wildlife Disease. 35(2): 319-330. Godfrey, W. E. 1986. The birds of Canada, rev. ed. National Museum of Canada. Ottawa, Ontario. Goodwin, C. E. and R. C. Rosche. 1972. Ontario-Western New York Region. American Birds. 26: 54-62. Grieco, F. 1999. Nest-site limitations and colony development in tree-nesting great cormorants. Waterbirds. 22: 417-423. Hartmann, W. L. 1988. Historical changes in the major fish resources of the Great Lakes. In Toxic contaminants and ecosystem health: a Great Lakes focus (Evans, M. S., ed.). Pg. 103-131. J. Wiley and Sons, New York. Hatch, J. J. 1995. Changing populations of double-crested cormorants. Colonial Waterbirds. 18 (Special Publications 1): 8-24. Hatch J. J. and D. V. Weseloh. 1999. Double-crested cormorant (Phalacrocorax auritus). In: The Birds of North America. No. 441 (Poole, A. and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA. 35 p. Havelka, T. and D. V. C. Weseloh. In Press. Continued growth and expansion of the double-crested cormorant (Phalacrocorax auritus) population on Lake Ontario, 1982-2002. Canadian Field-Naturalist. In Press. Haynes, R. J. and K. M. Goh. 1978. Ammonium and nitrate nutrition of plants. Biological Reviews. 53: 465–510. Hebert, C. E. and H. A. Morrison. 2003. Consumption of fish and other prey items by Lake Erie waterbirds. Journal of Great Lakes Research. 29(2): 213-227. Hebert, C. E., Duffe, J., Weseloh, D. V, Senese E. M., and G. D. Haffner. 2005. Unique island habitats may be threatened by double-crested cormorants. Journal of Wildlife Management. 69: 68-76. Hobara, S., Osono, T., Koba, K., Tokuchi, N., Fujiwara, S., and K. Kameda. 2001. Forest floor quality and N transformations in a temperate forest affected by avian-derived N deposition. Water, Air, and Soil Pollution. 130: 679-684. Hobson, K. A., Knapton, R. W., and W. Lysack. 1989. Population, diet, and reproductive success of double-crested cormorants breeding on Lake Winnipegosis, Manitoba, in 1987. Colonial Waterbirds. 12: 191-197.


________________________________________________________________________


Hogg, E. H. and J. K. Morton. 1983. The effects of nesting gulls on the vegetation and soil of islands in the Great Lakes. Canadian Journal of Botany. 61: 3240-3254. International Association of Fish and Wildlife Agencies. 2005. Proposal for an expanded flyway system. Non-game Migratory Bird Consultation Working Group. Bird Conservation Committee. 38 p. Ishida, A. 1996. Changes of soil properties in the colonies of the common cormorant, Phalacrocorax carbo. Journal of Forest Research. 1: 31-35. Ishida, A. 1997. Seed germination and seedling survival in a colony of the double-crested cormorant, Phalacrocorax auritus. Ecological Research. 12: 249-256. Jarvie, S., Blokpoel, H., and T. Chipperfield. 1999. A geographic information system to monitor nest distributions of double-crested cormorants and black-crowned night-herons at shared colony sites near Toronto, Canada. In Symposium on Double-crested Cormorants: Population status and management issues in the Midwest (Tobin, M. E., ed.). United States Department of Agriculture, Animal and Plant Health Inspection Service. Technical Bulletin 1879. Pg. 121-129. December 9, 1997. Johnsgard, P. A. 1993. Cormorants, darters, and pelicans of the world. Smithsonian Institute Press, Washington, D.C. xiv + 445 pp. Johnson, J.H., Ross, R.M., and D.R. Smith. 1997. Evidence of secondary consumption of invertebrate prey by double-crested cormorants. Colonial Waterbirds. 20: 547-551. Johnson, J.H., Ross, R. M., and C.M. Adams. 1999. Diet composition and fish consumption of double-crested cormorants in eastern Lake Ontario, 1998. Special Report. New York State Department of Environmental Conservation. Johnson, J. H., Ross, R. M., and R. D. McCullough. 2002. Little Galloo Island, Lake Ontario: a review of nine years of double-crested cormorant diet and fish consumption information. Journal of Great Lakes Research. 28(2): 182-192. Johnson, J. H., Klindt, R. M., Edmonds, B., and A. Bendig. 2003. Diet composition and fish consumption of double-crested cormorants from three St. Lawrence River colonies in 2002. New York State Department of Environmental Conservation Annual Report 2002, Section 17. Bureau of Fisheries Lake Ontario Unit and St. Lawrence River Unit to the Great Lakes Fishery Commission’s Lake Ontario Committee. Johnson, J. H., Klindt, R. M., Edmonds, B., and A. Bendig. 2004. Diet composition and fish consumption of double-crested cormorants from three St. Lawrence River colonies in 2003. New York State Department of Environmental Conservation Annual Report 2003, Section 17. Bureau of Fisheries Lake Ontario Unit and St. Lawrence River Unit to the Great Lakes Fishery Commission’s Lake Ontario Committee. Jones, M. L., Koonce, J. F., and R. O’Gorman. 1993. Sustainability of hatchery-dependent salmonid fisheries in Lake Ontario: the conflict between predator demand and prey supply. Transactions of the American Fisheries Society. 122: 1022-1028.


________________________________________________________________________


Kameda, K., Koba, K., Yoshimizu, C., Fujiwara, S., Hobara, S., Koyama, L., Tokuchi, N., and Takayanagi, A. 2000. Nutrient flux from aquatic to terrestrial ecosystem mediated by the great cormorant. Sylvia. 36 (Supplement): 54-55. Kamstra, J.M., M.J. Oldham, and P.A. Woodliffe. 1995. A life history inventory and evaluation of six natural areas in the Erie islands, Essex County, Ontario: Fish Point Provincial Nature Reserve, Lighthouse Point Provincial Nature Reserve, Stone Road Complex, Middle Point, East Sister Island Provincial Nature Reserve and Middle Island. Aylmer District, Ontario Ministry of Natural Resources, Aylmer, Ontario. Karwowski, K. 1994. Food study of the double-crested cormorant, Little Galloo Island, Lake Ontario, New York, 1992. Unpublished Admin. Report. U.S. Fish & Wildlife Service. Cortland, New York. 22 p. Kaufman, L. 1992. Catastrophic change in species-rich freshwater ecosystems. BioScience. 42: 846-858. Keith, A. J. 1966. Reproduction in a population of herring gulls (Larus argentatus) contaminated by DDT. Journal of Applied Ecology. 3: 57-70. King, D. T., Glahn, J. F. and K. J. Andrews. 1995. Daily activity budgets and movements of winter roosting double-crested cormorants determined by biotelemetry in the delta region of Mississippi. Colonial Waterbirds. 18 (Special Publication 1): 152-157. Klimkiewicz, M. K. and A. G. Futcher. 1989. Longevity records of North American birds. Journal of Field Ornithology. 60 (Supplement 1): 469-494. Koh, S. 2005. The effects of double-crested cormorants (Phalacrocorax auritus) on the forest habitats of East Sister Island, Lake Erie Canada: An assessment of damage and the construction of a preliminary carrying capacity model. TerraSystems Research. 29 p. Koh, S. and L.W. Carr. 2003. Follow-up assessment of tree damage: effect of double-crested cormorants on the western forest, High Bluff Island, Presqu’ile Provincial Park. TerraSystems Research. 27 p. Koh, S. and K. Hogsden. 2006. 2000-2004 assessment of forest damage: effects of double-crested cormorants on the western and eastern woodlots, High Bluff Island, Presqu’ile Provincial Park. TerraSystems Research. DRAFT. 32 p. Koonce, J. F. 1995. Aquatic community health of the Great Lakes. 1994 State of the Lakes Ecosystem Conference (SOLEC). Background paper, EPA 905-R-95-012. Burlington, Ontario: Environment Canada; and Chicago, Illinois: United States Environmental Protection Agency. Koonz, W. H. and P. W. Rakowski. 1985. Status of colonial waterbirds nesting in southern Manitoba. Canadian Field-Naturalist. 99(1): 19-29. Korfanty, C., Miyasaki, W. G., and J. L. Harcus. 1999. Review of the population status and management of double-crested cormorants in Ontario. In Symposium on Double-crested Cormorants: Population status and management issues in the Midwest (Tobin, M. E., ed.). United


________________________________________________________________________


States Department of Agriculture, Animal and Plant Health Inspection Service. Technical Bulletin 1879. Pg. 131-145. December 9, 1997. Krastina, E. E. and A. S. Loseva. 1975. The effect of the type of nitrogen nutrition on water uptake by plants and the concentration and ratio of cations in various organs. Isvestiva Timiryazevskoi Sel skokhozyaistvennoi Akademii. 5: 13-21. Kuiken, T., Frandsen, D., and A. Clavijo. 1998. Newcastle disease in cormorants. Canadian Veterinary Journal. 39(5): 299. Kuiken, T., Wobeser, G., Leighton, F.A., Haines, D.M., Chelack, B., Bogdan, J., Hassard, L., Heckert, R.A., and J. Riva. 1999. Pathology of Newcastle disease in double-crested cormorants from Saskatchewan, with comparison of diagnostic methods. Journal of Wildlife Disease. 35(1): 8-23. LaForest, S. M. 1993. Birds of Presqu'ile Provincial Park. The Friends of Presqu'ile Provincial Park. Brighton, Ontario. Lantry, B. F., Eckert, T. H., Schneider, C. P., and J. R. Chrisman. 2002. The relationship between the abundance of smallmouth bass and double-crested cormorants in the eastern basin of Lake Ontario. Journal of Great Lakes Research. 28(2): 193-201. Lemmon, C. R., Bugbee, G., and G. R. Stephens. 1994. Tree damage by nesting double-crested cormorants in Connecticut. Connecticut Warbler. 14: 27–30. Lewis, H. F. 1929. The natural history of the double-crested cormorant Phalacrocorax auritus (Leson). Ru-Mi-Lou Books. Ottawa, Ontario. Ligeza, S., Misztal, M., and P. Ciesielczuk. 2000. Nitrogen, phosphorus, and potassium compounds as the main factor of chemical soil degradation on the areas of cormorants’ and herons’ colonies. Zeszyty problemowe postepow nauk rolniczych. 472: 473–479. Ludwig, J. P. and C. S. Tomoff. 1966. Reproductive success and insecticide residues in Lake Michigan herring gulls. Jack Pine Warbler. 44: 77-85. Ludwig, J. P. 1984. Decline, resurgence and population dynamics of Michigan and Great Lakes double-crested cormorants. Jack-Pine Warbler. 62: 90-102. Ludwig, J. P., Hull, C.N., Ludwig, M.E., and H. J. Auman. 1989. Food habits and feeding ecology of nesting double-crested cormorants in the Upper Great lakes, 1986-1989. Jack-Pine Warbler. 67: 117-129. Madenjian, C. P. and S. W. Gabrey. 1995. Waterbird predation on fish in western Lake Erie: a bioenergetics model application. Condor. 97: 141-153. Mandrak, N. and E. J. Crossman. 2003. Fishes of Algonquin Park. The Friends of Algonquin Park. Ontario Parks. 40 p. McIntyre, J. D. 1955. First Record of a Double-crested Cormorant in Algonquin Park. Ontario Field Biologist. 9: 25.


________________________________________________________________________


McLeod, J. A. and G. F. Bondar. 1953. A brief study of the double-crested cormorant on Lake Winnipegosis. Canadian Field-Naturalist. 67: 1-11. Meister, A. L. and F. J. Gramlich. 1967. Cormorant predation on tagged Atlantic salmon smolts. Maine Atlantic Sea-Run Salmon Commission. Unpublished report. University of Maine, Orono. 36 p. Mills, E. L., Leach, J. H., Carlton, J. T., and C. L., Secor. 1993. Exotic species in the Great Lakes: a history of biotic crises and anthropogenic introductions. Journal of Great Lakes Research. 19(1): 1-54. Mills, E. L., Casselman, J. M., Dermott, R., Fitzsimons, J. D., Gal, G., Holeck, K. T., Hoyle, J. A., Johannsson, O. E., Lantry, B. F., Makarewicz, J. C., Millard, E. S., Munawar, I. F., Munawar, M., O’Gorman, R., Owens, R. W., Rudstam, L. G., Schaner, T., and T. J. Stewart. 2005. A synthesis of ecological and fish community changes in Lake Ontario, 1970-2000. Great Lakes Fishery Commission. Technical Report 67. Mineau, P. and R. Markel. 1979. The 1979 spring bird migration and other vertebrates at Middle Island, Lake Erie. Ontario Field Biologist. 35: 13-21. Moore, D. J., Blokpoel, H., Lampman, K. P., and D. V. Weseloh. 1995. Status, ecology and management of colonial waterbirds nesting in Hamilton Harbour, Lake Ontario, 1988 – 1994. Technical Report Series No. 213. Canadian Wildlife Service, Ontario Region, Burlington, Ontario. Moore, D. J., Weseloh, D. V. C., and R. Boos. 2005. The management of double-crested cormorants (Phalacrocorax auritis) and its effects on great blue heron (Ardea herodias) and great egrets (Ardea albus) at High Bluff Island (Lake Ontario) in 2005. DRAFT. Unpublished Report. Montevecchi, W. A. and J. F. Piatt. 1987. Dehydration of seabird prey during transport to the colony: effects of wet weight energy densities. Canadian Journal of Zoology. 65: 2822-2924. Montevecchi, W. A., Cairns, D. K. and V. L. Birt. 1988. Migration of post-molt Atlantic Salmon, Salmo salar, off northeastern Newfoundland, as inferred by tag recoveries in a seabird colony. Canadian Journal of Fisheries and Aquatic Sciences. 45: 568-571. Neuman J., Pearl, D. L., Ewins, P. J., Black, R., Weseloh, D. V., Pike, M., and K. Karwowski. 1997. Spatial and temporal variations in the diet of Double-crested cormorants (Phalacrocorax auritus) breeding on the lower Great Lakes in the early 1990s. Canadian Journal of Fisheries and Aquatic Science. 54: 1569-1584. Nisbet, I. C. T. 1995. Biology, conservation and management of the double-crested cormorant: symposium summary and overview. Colonial Waterbirds. 18 (Special Publication 1): 247-252. Omand, D. N. 1947. The cormorant in Ontario. Sylva. 3: 18-23. Ontario Breeding Bird Atlas (OBBA). 2005. Ontario Breeding Bird Atlas Database Updates. National Data Center. Bird Studies Canada. Port Rowan, Ontario.


________________________________________________________________________


Ontario Ministry of Natural Resources (OMNR). 1992. Ontario Provincial Parks: Planning and Management Policies. 1992 Update. Ontario Parks. Queens Printer for Ontario. Ontario Ministry of Natural Resources (OMNR). 1997. Review of the population status and management of double-crested cormorants in Ontario. Fish and Wildlife Branch. Wildlife Section. Peterborough, Ontario. 31 p. Ontario Ministry of Natural Resources (OMNR). 1998. Algonquin Park Management Plan. Algonquin Provincial Park. Ontario Parks. Queens Printer for Ontario. Ontario Ministry of Natural Resources (OMNR). 2000. Presqu’ile Provincial Park Management Plan. Ontario Parks. 36 p. Ontario Ministry of Natural Resources (OMNR). 2002. Presqu’ile Provincial Park management strategy for double-crested cormorants. Ontario Parks. 19 p. Ontario Ministry of Natural Resources (OMNR). 2003. East Sister Island Provincial Nature Reserve, Park Management Plan, Terms of Reference. Ontario Parks - Park Management Planning Process. Ontario Parks. 10 p. Ontario Ministry of Natural Resources (OMNR). 2004(a). Annual report on the management of double-crested cormorants at Presqu’ile Provincial Park for 2004. Ontario Parks. 25 p. Ontario Ministry of Natural Resources (OMNR). 2004(b). Amendment of the management strategy for double-crested cormorants at Presqu’ile Provincial Park. Ontario Parks. 26 p. Ontario Ministry of Natural Resources (OMNR). 2005(a). Fact Sheet – Double-crested Cormorants in Ontario. Fish and Wildlife Branch. Peterborough, Ontario. Ontario Ministry of Natural Resources (OMNR). 2005(b). Annual report on the management of double-crested cormorants at Presqu’ile Provincial Park for 2005. Ontario Parks. DRAFT. Ontario Ministry of Natural Resources (OMNR). 2005(c). Algonquin Park Museum Bird Database. Algonquin Provincial Park Visitor Centre. Ontario Parks. Ontario Ministry of Natural Resources (OMNR). 2005(d). Our Sustainable Future. Ministry of Natural Resources Strategic Directions. Ontario Ministry of Natural Resources. Queens Printer for Ontario. Ontario Ministry of Natural Resources (OMNR). 2005(e). Ontario’s Biodiversity Strategy – protecting what sustains us. Ontario Ministry of Natural Resources. Queens Printer of Ontario. Palmer, R. S., ed. 1962. Handbook of North American birds. Volume 1. Yale University Press. New Haven, Connecticut. Peck, G. K. and R. D. James. 1983. Breeding birds of Ontario: Nidiology and Distribution. Volume 1: Nonpasserines. Royal Ontario Museum. Life Sciences Miscellaneous. Publications. Toronto.


________________________________________________________________________


Pekarik, C., Weseloh, D. V., Barett, G. C., Simon, M., Bishop, C. A. and K. E. Pettit. 1998. An atlas of contaminants in eggs of colonial fish-eating birds of the Great Lakes (1993-1997). Accounts by location: Volume I, Technical Report No. 321, 245 p. and accounts by chemical: Volume II, Technical Report No. 322, 214 p. Canadian Wildlife Service. Ontario Region. Burlington, Ontario. Pettit, K. E., Bishop, C. A., Weseloh, D. V., and R. J. Norstrom. 1994. An atlas of contaminants in eggs of colonial fish-eating birds of the Great Lakes (1989-1992). Accounts by location: Volume I, Technical Report No. 193, 319 pp. and accounts by chemical: Volume II, Technical Report No. 194, 300 p. Canadian Wildlife Service. Burlington, Ontario. Postupalsky, S. 1978. Toxic chemicals and cormorant populations in the Great Lakes. Canadian Wildlife Service, Wildlife Toxicology Division, Manuscript Report No. 40, Ottawa, Ontario. Price, I. M. and D. V. Weseloh. 1986. Increased numbers and productivity of double-crested cormorants, Phalacrocorax auritus, on Lake Ontario. Canadian Field-Naturalist. 100(4): 474-482. Quinn, N. W. S., Korver, R., Hicks, F., Monroe, B., and R. Hawkins. 1994. An empirical model of lentic brook trout. North American Journal of Fisheries Management. 14: 692-709. Quinn, J. S., Morris, R. D., Blokpoel, H., Weseloh, D. V., and P. J. Ewins. 1996. Design and management of bird nesting habitat: tactics for conserving colonial waterbird biodiversity on artificial islands in Hamilton Harbour, Ontario. Canadian Journal of Fisheries and Aquatic Sciences. 53 (Supplement 1): 43-57. Rail, J. and G. Chapdelaine. 1998. Food of double-crested cormorants, Phalacrocorax auritus, in the Gulf and Estuary of the St. Lawrence River, Quebec, Canada. Canadian Journal of Zoology. 76: 635-643. Ratcliff, B. 2004. Breeding History and Diet Composition of Double-crested Cormorant (Phalacrocorax auritus) Colonies on Black Bay and Thunder Bay, Lake Superior in 2003. Upper Great Lakes Management Unit – Lake Superior. Ontario Ministry of Natural Resources. Thunder Bay, ON. 11 p. Ricciardi, A. 2001. Facilitative interactions among aquatic invaders: is an “invasional meltdown” occurring in the Great Lakes? Canadian Journal of Fisheries and Aquatic Sciences. 58: 2513-2525. Richards, J.M. 1989. The status of colonial waterbirds on Gull and High Bluff Islands, Presqu’ile Provincial Park in 1989. Unpublished Report. 2 p. + map. Ridgway, M. S. 2005. Increase and recent decline of double-crested cormorants in coastal areas of Lake Huron: implications for fish biomass consumption. International Association for Great Lakes Research. 48th Annual Conference. May 23-27, 2005. University of Michigan. Ann Arbour, Michigan. Ridgway, M. S., Milne, S. M., Middel, T., and J. M. Casselman. 2006. Double-crested cormorant and coastal fish monitoring and assessment in the North Channel and Georgian Bay,


________________________________________________________________________


Lake Huron. Aquatic Research and Development Section, Ontario Ministry of Natural Resources. Peterborough, Ontario. 67 p. + appendices. Rippey, E., Rippey, J. J., and J. N. Dunlop. 2002. Increasing numbers of pied cormorants breeding on the islands off Perth, Western Australia and the consequences for the vegetation. Corella. 26: 61–64. Roney, K. 1979. Preliminary results on the food consumed by nesting double-crested cormorants at Cypress Lake, Saskatchewan. Proceedings of the Colonial Waterbird Group Conference. 3: 257-258 (Abstract only). Ross, R. M., and J. H. Johnson. 1994. Feeding ecology of double-crested cormorants in eastern Lake Ontario. Paper presented at joint annual meeting of the New York chapters of The Wildlife Society and the American Fisheries Society. January 26-28. Owego, New York. Ross, R. M. and J. H. Johnson. 1995. Seasonal and annual changes in the diet of double-crested cormorants: implications for Lake Ontario’s fishery. Great Lakes Research Review. 2:1-9. Ross, R. M. and J. H. Johnson. 1999. Fish losses to double-crested cormorant predation in eastern Lake Ontario, 1992-97. In Symposium on Double-crested Cormorants: Population status and management issues in the Midwest (Tobin, M. E., ed.). United States Department of Agriculture, Animal and Plant Health Inspection Service. Technical Bulletin 1879. Pg. 61-72. December 9, 1997. Rowe, R. 2003. The double-crested cormorant population of Lake Nipissing: a case study. Ontario Ministry of Natural Resources. North Bay District Resource Report. 4 p. Rudstam, L. G., Van De Valk, A. J., Adams, C. M., Coleman, J. T. H., Forney, J. L., and M. E. Richmond. 2004. Cormorant predation and the population dynamics of walleye and yellow perch in Oneida Lake. Ecological Applications. 14(1): 149-163. Ryckman, D. P., Weseloh, D. V., Hamr, P., Fox, G. A., Collins, B., Ewins, P. J., and R. J. Norstrom. 1998. Spatial and temporal trends in organochlorine contamination and bill deformities in double-crested cormorants (Phalacrocorax auritus) from the Canadian Great Lakes. Environmental Monitoring and Assessment. 53: 169-195. Sandilands, A. P. 2005. The Birds of Ontario: Habitat Requirements, Limiting Factors and Status. University of British Columbia Press. Vancouver, British Columbia. Schaeffer, J. S., O'Brien, T. P., Warner, D. M., and E. F. Roseman. 2006. Status and trends of pelagic prey fish in Lake Huron, 2005: results from a lake-wide acoustic survey. United States Geological Survey Report, Great Lakes Technical Meeting, Windsor Ontario. Scharf, W. C. and G. W. Shugart. 1998. Distribution and abundance of gull, tern and cormorant nesting colonies of the U.S. Great Lakes, 1989 and 1990. (Bowerman, W. W. and A. S. Roe, eds.). Publication No. 1, Gale Gleason Environemntal Instititute, Lake Superior State University Press, Sault Ste. Marie, Michigan.


________________________________________________________________________


Schneider, C. P., Schiavone, A., and McCullough, R. D. 1996. The impact of double-crested cormorant predation on smallmouth bass stocks in the eastern basin of Lake Ontario. New York Department of Environmental Conservation Lake Ontario Annual Report. Schneider, C. P., Schiavone, A., Jr., Eckert, T. H., McCullough, R. D., Lantry, B. F., Einhouse, D. W., Chrisman, J. R., Adams, C. M., Johnson, J. H., and R. M. Ross. 1998. Double-crested cormorant predation on smallmouth bass and other warm water fishes of the eastern basin of Lake Ontario: overview and summary. New York Department of Environmental Conservation Special Report. December 15, 1998. Schramm, H. L., French, B., and M. Ednoff. 1984. Depredation of channel catfish by Florida double-crested cormorants. Progressive Fish-Culturalist. 46: 41-43. Shieldcastle, M. C. and L. M. Martin. 1999. Colonial waterbird nesting on West Sister Island Wildlife Refuge and the arrival of double-crested cormorants. In Symposium on Double-crested Cormorants: Population status and management issues in the Midwest (Tobin, M. E., ed.). United States Department of Agriculture, Animal and Plant Health Inspection Service. Technical Bulletin 1879. Pg. 115-120. December 9, 1997. Shutt, J. L., Weseloh, D. V., Pekarik, C. and J. Robinson. 2005. Type E botulism-related mortality in colonial waterbirds in eastern Lake Ontario: implications for the health of waterbird populations. International Association for Great Lakes Research. 48th Annual Conference. May 23-27, 2005. University of Michigan. Ann Arbour, Michigan. Simmonds, R. L., Zale, A. V., and D. M. Leslie. 2000. Modeled effects of double-crested cormorant predation on simulated reservoir sport and forage fish populations in Oklahoma. North American Journal of Fisheries Management. 20: 180-191. Somers, C. M., Lozer, M. N. and J. S. Quinn. In Review. Double-crested cormorants (Phalacrocorax auritus) reduce reproductive success in herring gulls (Larus argentatus) at a shared nesting site. Waterbirds. In Review. Stapanian, M. A., Bur, M. T., Tyson, J. T., Seamans, T. W., and B. F. Blackwell. 2002. Foraging locations of double-crested cormorants on western Lake Erie: characteristics and spatial associations with prey fish densities. Journal of Great Lakes Research. 28(2): 155-171. Stenzel, L. E., H. R. Carter, R. D. Henderson, S. D. Emslie, and J. D. Rauzon. 1995. Breeding success of Double-crested Cormorants in the San Francisco Bay area, California. Colonial Waterbirds. 18 (Special Publication 1): 216-224. Stickley, A. R., Jr., Warrick, G. L., and J. F. Glahn. 1992. Impact of double-crested cormorant populations on channel catfish farms. Journal of the World Aquaculture Society. 23: 192-198. Tanner, J. 1994. The falcon: a narrative of the captivity and adventures of John Tanner during thirty years residence among the Indians in the interior of North America. Penguin Books, New York. 62 p. Toronto and Region Conservation Authority (TRCA). 1989. Tommy Thompson Park Master Plan and Environmental Assessment. MTRCA.


________________________________________________________________________


Toronto and Region Conservation Authority (TRCA). 1992. Tommy Thompson Park Master Plan and Environment Assessment Addendum. MTRCA. Townsend, C. W. and A. C. Bent. 1910. Additional notes on birds of Labrador. Auk. 27: 1-18. Tracey, A.G., MacDonald, I. D., and T.J. Beechey. 1971. East Sister Island, Essex County, Ontario: a natural science inventory report. Parks Branch, Ontario Department of Lands and Forests, Toronto. Trapp, J. L., Lewis, S. J., and D. M. Pence. 1999. Double-crested cormorant impacts on sport fish: Literature review, Agency survey and strategies. In Symposium on Double-crested Cormorants: Population status and management issues in the Midwest (Tobin, M. E., ed.). United States Department of Agriculture, Animal and Plant Health Inspection Service. Technical Bulletin 1879. Pg. 87-98. December 9, 1997. United States Fish and Wildlife Service (USFWS). 2003. Final Environmental Impact Statement – Double-crested Cormorant Management in the United States. Department of the Interior, U.S. Fish and Wildlife Service and Department of Agriculture, Animal and Plant Health Inspection Service. Washington, D.C. Van der Veen, H. E. 1973. Some aspects of the breeding biology and demography of the Double-crested Cormorants (Phalacrocorax auritus) of Mandarte Island. Ph.D. Thesis, Zoologisch Laboratorium der Rijksuniversiteit te Groningen, Groningen. Van De Valk, A. J., Rudstam, L. G., Brooking, T., and A. Beitler. 1999. Walleye stock assessment and population projections for Oneida Lake, 1998-2001. New York Federal Aid Study VII, Job 103. FA-5-R. Van De Valk, A. J., Adams, C. M., Rudstam, L. G., Forney, J. L., Brooking, T. E., Gerken, M. A., Young, B. P., and J. T. Hooper. 2002. Comparison of angler and cormorant harvest of walleye and yellow perch in Oneida Lake, New York. Transactions of the American Fisheries Society. 131: 27-39. Vascotto, K. 2004. Long-Term Changes in Dickson Lake and Proposal for Further Investigations. Ontario Ministry of Natural Resources. Algonquin Park Fisheries Assessment Unit. Unpublished report. Vermeer, K. and L. Rankin. 1984. Population trends in nesting double-crested cormorants and pelagic cormorants in British Columbia. Murrelet. 65: 1-9. Weseloh, D.V.C. 1996. History and continued growth of the double-crested cormorant populations on the Great Lakes in the mid-1990s. Bird Trends. 5:23-25. Weseloh, D. V. and R. T. Brown. 1971. Plant distribution within a heron rookery. American Midland Naturalist. 86: 57-64. Weseloh, D. V. and J. Casselman. 1992. Calculated fish consumption by double-crested cormorants in eastern Lake Ontario. Colonial Waterbird Society Bulletin. 16(2): 63-64 (Abstract only).


________________________________________________________________________


Weseloh, D. V. and J. M. Casselman. 1994. Fish consumption by double-crested cormorants on Lake Ontario. Unpublished manuscript. 16 p. Weseloh, D. V. C., and P. J. Ewins. 1994. Characteristics of a rapidly increasing colony of double-crested cormorants (Phalacrocorax auritus) in Lake Ontario: population size, reproductive parameters, and band recoveries. J. Great Lakes Res. 20(2): 443-456. Weseloh, D.V. and B. Collier. 1995. The rise of the Double-crested Cormorant on the Great Lakes: Winning the war against contaminants. Great Lakes Fact Sheet. Canadian Wildlife Service, Environment Canada and Long Point Observatory. Environment Canada. Weseloh, D. V. C. and S. J. Lewis. 1999. Information needs for the double-crested cormorant in Midwestern North America, as identified by an audience survey. In Symposium on Double-crested Cormorants: Population status and management issues in the Midwest (Tobin, M. E., ed.). United States Department of Agriculture, Animal and Plant Health Inspection Service. Technical Bulletin 1879. Pg. 157-158. December 9, 1997. Weseloh, D.V. and C. Pekarik. 1999. Declining contaminant levels in herring gull eggs from Toronto Harbour, Lake Ontario, 1974-1998. Great Lakes Research Review. 4(2): 23-27. Weseloh, D.V.C. and J. L. Shutt. 2005. A brief history and current status of Double-crested Cormorant colonies on Lake Ontario, 2003 – 2004. Unpublished manuscript, Canadian Wildlife Service, Downsview, Ontario. Weseloh, D. V., Teeple, S. M., and M. Gilbertson. 1983. Double-crested cormorants of the Great Lakes: egg-laying parameters, reproductive failure, and contaminant residues in eggs, Lake Huron, 1972-1973. Canadian Journal of Zoology. 61: 427-436. Weseloh, D.V., Ewins, P.J., Struger, J., Mineau, P., Bishop, C.A., Postupalsky, S., and J.P. Ludwig. 1995. Double-crested cormorants of the Great Lakes: Changes in population size, breeding distribution and reproductive output between 1913 and 1991. Colonial Waterbirds. 18 (Special Publication 1): 48-59. Weseloh, D. V., Hamr, P., Bishop, C.A., and R. J. Norstrom. 1995(b). Organochlorine contaminant levels in waterbird species from Hamilton Harbour, Lake Ontario: An IJC Area of Concern. Journal of Great Lakes Research. 21(1): 121-137. Weseloh, D.V.C., Cuthbert, F., Wires, L., Pekarik, C., Havelka, T., Farquhar, J., and M. Shieldcastle. 2000. Population estimates of breeding double-crested cormorants on the Great Lakes, 2000. Abstracts. Cormorant Symposium 31 October 2000 (The Waterbird Society 24th Annual Meeting). Plymouth, Massachusetts. Weseloh, D.V.C., Pekarik, C., Havelka, T., Barrett, G., and J. Reid. 2002. Population trends and colony locations of double-crested cormorants in the Canadian Great Lakes and immediately adjacent areas, 1990-2000: A Manager’s Guide. Journal of Great Lakes Research. 28: 125-144. Weseloh, D. V., Pekarik, C., Joos, R., Farquhar, J. F., Shutt, J. L., Havelka, T., Mazzocchi, I., Barrett, G., McCollough, R., Miller, R. L. and A. Mathers. 2003. Monitoring Lake Ontario’s waterbirds: contaminants in herring gull eggs and population changes in the lake’s nearly 1,000,000 colonial waterbirds. In State of Lake Ontario – Past, Present and Future. Munawar, M.


________________________________________________________________________


(ed.). pp.597-631. Ecovision World Monograph Series. 2003 Aquatic Ecosystem Health and Management Society. Backhuys Publishers. Leiden, The Netherlands. Weseloh, D. V., Pekarik, C. and T. Havelka. 2005. The Status of Black-crowned Night-Heron Colonies on the Great Lakes vis a vis Encroachment by Nesting Double-crested Cormorants. International Association for Great Lakes Research. 48th Annual Conference. May 23-27, 2005. University of Michigan. Ann Arbour, Michigan. Weseloh, D. V. C., Havelka, T., Cuthbert, F. and Hanisch, S. 2006. The 2005 Great Lakes-wide census of nesting double-crested cormorants. Draft Report of Results. January 13, 2006. Unpublished Manuscript. Canadian Wildlife Service. Downsview, Ontario. Weseloh, D. V. C., Havelka, T. and C. Pekarik. In Press. Double-crested cormorants on the Lower Great Lakes: a 2004 update on nest numbers and management actions. Bird Trends. In Press. Wetmore, A. 1927. The amount of food consumed by cormorants. Condor. 29: 273-274. White, D.J. and M.J. Oldham. 2000. COSEWIC Status Report Update on Kentucky Coffee-Tree (Gymnocladus dioicus). Committee on the Status of Endangered Wildlife in Canada. Pg. 1-8. Wiese, F. K., Parrish, J. K. and C. W. Thompson. 2005. Adaptive management of predator-prey linkages: piscivorous birds and endangered salmon in the Columbia River. Abstract Only. 32nd Annual Meeting of the Pacific Seabird Group. 27th Annual Meeting of the Waterbird Society. Portland, Oregon. January 19-22, 2005. Wires, L. R. and F. J. Cuthbert. 2006. Historic populations of the double-crested cormorant (Phalacrocorax auritus): implications for conservation and management in the 21st century. Waterbirds. 29(1): 9-37. Wires, L.R., Cuthbert, F.J., Trexel, D.R. and A.R. Joshi. 2001. Status of the double-crested cormorant (Phalocrocoras auritus) in North America. Final Report to the U.S. Fish and Wildlife Service. Wywialowski, A. P. 1999. Wildlife-caused losses for producers of channel catfish (Italurus punctatus) in 1996. Journal of the World Aquaculture Society. 30: 461-472. Yabsley, M.J., Gottdenker, N.L., and J.R. Fischer. 2002. Description of a new Eimeria sp. and associated lesions in the kidneys of double-crested cormorants (Phalocrocorax auritus). Journal of Parasitology. 88(6): 1230-1233.

Documents

Review of the Status and Management of Double-crested ...bays or inlets to enhance foraging success (Glanville 1992). The diet of cormorants has been studied extensively in North America