Double-crested Cormorants of the NY Harbor

2010 Harbor Herons and Waterbirds …

Susan Elbin , New York City AudubonLiz Craig, New York City Audubon and Cornell University

Cormorants

Year 2005 2006 2007 2008 2009 2010Nests 906 1175 1046 1384 1218 1411

Islands

6 6 7 7 7 8

Banded

0 198 240 225 255 201

Double-crested Cormorant Birds Banded in the NY Harbor

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

2008

2010

0400800

120016002000

Gulls in Jamaica Bay 2010 Update

Dr. Brian E. Washburn

USDA, APHIS, Wildlife Services, National Wildlife Research Center

419-625-0242brian.e.washburn@aphis.usda.gov

Research Objective

Estimate the size of gull nesting populations in the Jamaica Bay Unit of Gateway NRA

Jamaica Bay Nest Count for 2010

20 islands & marshes

May 27 to June 8, 2010

Multi-agency effort

Count of adult gulls & count of gull nests

Count of Adult Gulls Marsh HERG GBBG

Canarsie Pol 730 49

Subway Island 245 13

Elder’s Point East 60 2

Little Egg Marsh 95 120

Broad Creek Marsh 30 0

Duck Point Marsh 6 0

TOTAL 1,166 184

Count of Gull Nests Marsh HERG GBBG

Canarsie Pol 126 7

Subway Island 69 1

Elder’s Point East 49 2

Little Egg Marsh 95 120

Broad Creek Marsh 30 0

Duck Point Marsh 6 0

TOTAL 375 130

JFKIAHERG

JFKIAGBBG

JFKIALAGU

Research Objective

Estimate the population of laughing gull nests in Jamaica Bay

Aerial Photography Approach

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

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2003

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2005

2006

2007

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2009

2010

E. Joco IslandSilver HoleE. H. MeadowJoco

No

estim

ate

Num

ber o

f LA

GU

Nes

ts

No

estim

ate

Joco Marsh

East High

Meadow

Silver Hole

East Joco

Island

Total Colony

2007 1,322 8 13 3 1,346

2008 1,237 13 21 9 1,280

2010 2,672 117 0 53 2,932

Diet of Double-crested Cormorants in NY Harbor,

2010 update

Colin Grubel, CUNY Graduate Center & Queens College

John Waldman, Queens College

Colony comparisons

South Brother 4 collection trips 83 items

identified 15 sp. fish, 1

crustacean Most common

sp: Hogchokers (24%) & goldfish (22%)

Swinburne 2 collection trips 72 items

identified 18 sp. fish, 1

crustacean Most common

sp: spotted hakes (29%)

Conclusions Swinburne results from trips close

together Can’t be easily extrapolated to rest of

season No new species found Rarity of formerly popular species (scup,

black seabass) and unusual popularity of hakes may be due to

South Brother surveyed more thoroughly than previous years 1 new species (white sucker) Bluegills, Lepomis macrochirus, and

Pumpkinseeds, Lepomis gibbosus, usually common, not found

Investigations into the Factors

Affecting Pellet Production

Introduction Diet studies are an important part of

management Boli & pellets most common methods of

diet assessment Boli (regurgitated, partially digested food

items) Pellets (made up of bones, scales, otoliths

and other indigestible items, contained in a mucous coat and regurgitated by the birds)

Otoliths are akin to ear bones of fish – highly species specific

Species not represented equally between pellets and boli

Good evidence of biases but no evidence as to exactly what is causing them

Feeding Trials Prey spininess Otolith

morphology Prey size

• Two enclosures, housing 3 birds• Floors lined with Astroturf to prevent sand

accumulation• Colored glass beads inserted into fish being fed out -

help quantify the time each pellet has taken to form

Prey Spininess Hypothesized that spines present on

some species of fish may irritate the gut Would speed up pellet production Less time in gut would mean more

otoliths surviving in pellet

Previous fieldwork indicated spininess as a possible factor affecting pellet production 52% of fish identified in bolus samples

were spiny, 48% were non–spiny 95% of fish identified in pellets were spiny,

5% were non-spiny

Otolith Morphologies Compact

otoliths Croaker

Scad

Pinfish

goldfish Fragile otoliths

Threadfin herring

False pilchard

Otoliths by size Croaker (avg length

10.12µ) Scad (6.94µ) Pinfish (3.7µ) Large threadfin

(3.57µ) Small threadfin &

false pilchard (2.53µ)

Goldfish*

Conclusions The timing of pellet production

may be affected my spininess of prey species but results inconclusive

Length of captivity appears to play a part as well, reason unknown Process may be different in wild

birds Otolith shape can affect the

likelyhood of surviving to be ejected and identified in a pellet

Otolith size may also be important but more research needed