Appendix V.Population Biology: Red Knot Final Presentation

8/7/2019 Appendix V. Population Biology: Red Knot Final Presentation

http://slidepdf.com/reader/full/appendix-v-population-biology-red-knot-final-presentation 1/37

Marie Cook



Taxonomy

Kingdom: Animalia Phylum: Vertebrata

Class: Aves

Order: Scolopacidae Family: Charadriiformes

Genus: Calidris

Species: canutus Subspecies: islandica , rufa , roselaari,

rogersi, piersmai, and canutus



Genus Calidris

Commonly referred to as “waders” or “peeps” Small to medium-sized shorebirds with long wings and relatively short bills

Found locally in large mixed flocks alongcoastal estuaries, feeding via plucking, probing,and plowing

Arctic breeders that undergo long-hopmigrations

Members include Sandpipers, Dunlins, andStints



Calidris canutus: Brief Description Largest member of Calidris with stocky body Comparatively short bill, short legs About the size of an

American Robin Dull grey non-breeding

and bright red breeding

plumages Breed monogamously by

season in high arcticclimates and winter intropical or subtropicalclimates

Make one of the longestannual migrations,utilizing stopovers between jumps

Six subspecies recognized, varying geographically, and morphologically in terms of plumage, and wing and bill lengths.

Global population ≈ 1,050,000 birds



Calidris canutus Subspecies



Subspecies (cont’d)

North American subspecies C. c. rufa shows

lowest estimated population size.



Differences Among Subspecies Divergence

Last common ancestor can be traced to about 20,000 years before present.

This was about the time of the end of the last Ice Age. As ice retreated, populations dispersed throughout new

suitable habitats.

North American subspecies, rufa and roselaari diverged

about 1,200 years ago. Differences in Morphology

Wing and bill length

Brightness and patterns of plumage



Migration Strategy Fly thousands of miles without rest = long hop

migrant

Travel in species-specific f locks due to differences inspeed, altitude, and flock configuration preferences

among shorebirds Fly in wind tunnels to decrease energy costs of flight.

Decrease in digestive organ size for increased space forfat reserves

Increase flight muscle mass to endure long-distancemigration

Departure times, ranges, routes, and stopovers vary among subspecies

Non-breeding juveniles may not migrate to Arctic.



Metabolism During Migration

Products of lipid and protein metabolism are associated withflight. Highest in birds just arriving at

stopover Intermediate in refueling birds Lowest in inactive birds

Energy required during long-distancemigratory flight is largely acquired fromfat.

Supplemented by protein metabolism

Found to be mostly proportional tointensity of activity Provides compounds for citric acid cycle Explains why so many birds arrive at stopovers with largely

decreased flight muscles Organ reduction serves as evidence for protein use.



Tissue and Organ Plasticity Brain seems to be only homeostatic organ Large changes seen mainly in digestive organs

Negative relationship suggested between fat storage andreduction of size in kidneys, liver, and intestine

Organs aren’t used during migration Lessens maintenance cost

Lowers basal metabolic rate

Releases protein to be metabolized

Allows protection from breakdown of more crucial organs

Gizzard sizes are also reduced. HSC eggs are easily digested, allowing maintenance of

reduced gizzard during refueling.

Lean muscle mass increases while staging



Reasons for Northward Migration Reduced Competition and Predation

The harsh environment of the high arcticis conducive to less organisms, includingparasites.

Cryptic plumage and widely dispersed

large nest territories make knots harderfor predators to find.

Increased Resources During the short arctic summer, the sun

shines all or most of the day long,

creating a superabundance of plants andinsects. This nutrition is crucial for courtship,

reproduction, and nest success. Knots time their migration on the

availability of resources.



Predation at High Latitudes Nest predation negatively

proportional to latitude

Reduced predationcompensates for risks that

increase with latitude: Migration

High mortality

Poor weather conditions

At right, percent decrease of predation on artificial nests with latitude (McKinnon2010).



C. c. rufa Population decline

1980s = 100,000-150,000 knots

2006 = 17,200 knots

Four wintering ranges Mainly Florida, but also Georgia, and

South Carolina

Texas

Northern Brazil

Tierra del Fuego (TDF) Staging sites

Northward

Argentina

Venezuela

Delaware Bay

Southward James and Hudson Bays

Massachusetts, Connecticut, Rhode Island

Brazil

Breeding range

Central Canadian Arctic from

Southampton Island to Victoria Island



Distribution of C. c. rufa



Breeding Range Arrive in Arctic tundra in June to claim nesting

sites, depart in mid-July to early August Live territorially on slopes and cliffs that are within

easy access to wetlands Territory area 1.5 km2

Show high site fidelity Thrive on grasses and

their seeds until insectsemerge upon snowmelt

Predators include ArcticFox, Snowy Owls, and a

variety of Jaegers, whichprey upon eggs and chicks.

Nest success ≈ 75% (conservative)



Reproduction

Reach sexual maturity aroundage 2 Males usually arrive first to claim

nesting territory. Males build up to 5 scrapes out of

vegetation

Males perform displays includingsong f lights during courtship.

Female is fertilized via cloacal kiss

from male. One brood laid per year Clutch size = 3 or 4 eggs Incubation by males and females for

around 22 days; females first to leave Chicks born precocial; fledge after 18

days



Limiting Factors of Recruitment Density-dependent:

Food, foraging success

Suitable nest sites

Predation

At right, % juveniles vs.index of winteringpopulation numbers A = before 1969

B = 1969-1995

(Boyd & Piersma 2001) Density-independent:

Weather conditions inbreeding grounds

Stochastic events



Predation of Chicks Largely by Arctic fox

Affected by predatory/prey cycles of Arctic fox and

lemmings Lemmings on 3-4 year cycle

When lemming population islow, chicks are alternate prey.

Predation of lemmings releasespressure on knot population.

Eggs and chicks predated increasepredator population.



Prevention of Nest Predation Adult plumage, nests, and egg coloration are cryptic. Males protect territory with ground and aerial displays. Shift in chemistry of preen wax

Monoester waxes are easily detected by olfactory hunters. Maintained in ranges withoutmammalian predators

Upon breeding, compositionswitches to diester. Less concentrated Harder to detect olfactorily Shift is energetically costly

At right (Reneerkens, et al . 2005),detection success of sniffing dog Solid line = monoester wax Dashed line = diester wax



Coastal Range: Wintering and Staging

Arrive in wintering sites in October and depart in late January and early February

Live gregariously in coastal wetlands

Found in mixed flocks of shorebirds like dowitchers, plovers,turnstones, and other sandpipers.

Forage by pecking and probing soft substrate for marine invertebrateslike bivalves, crustaceans, and small snails

Predators and competitors include Peregrine Falcons, harriers, GreatBlack-Backed Gulls, and other birds of prey.



Foraging Probe upper 3cm of moist

sandy substrate

Herbst corpuscles Pressure sensory organs in

bill Allow detection of buried

prey and stones

Uses water molecules in

pores of sand to sensechanges in pressure aroundobject

Electron microscope imagesat right; bottom image x100



Foraging (Cont’d) Efficiency affected by: Tides – foraging area only

available at low tide Prey density – positive

relationship Predation – negative

relationship Disturbance – presence of

humans, dogs, gulls, etc. Ideal

Timed with prey availability Increased energy storage

Non-free

Travel from foraging to roostingsites is energetically costly Seem to choose foraging sites

based on closeness to saferoosting sites

At left, observations match

most closely to predicted modelfor ideal, non-free foragers



Delaware Bay Stopover

Second largest stopover in the world, utilized by 425,000 to1,000,000 migratory shorebirds

Last stopover before over 9,000mile migration to reachbreeding grounds

Knots begin to arrive in early May and depart for breedinggrounds in late May and early June.

Shorebirds depend on horseshoe

crab eggs to refuel. Delaware Bay is a prime spawning

area for Horseshoe Crabs. Knots need to about double body

mass from 90-120g – 180-220g toensure survival and breeding success.

Refueling success depends on arrivaltime and prey availability.



Harvesting increased in the 1990s by almost 10 times Eel and conch bait LAL medical testing to detect bacterial endotoxins Responsible for 90% decrease in egg availability

From 1992 to 1997, the reported harvest of crabs increased by 20

times from about 100,000 to more than 2 million. By 2004, harvest still exceeded production. Recovery will be slow since HSCs don’t mature until about age 10. Importance of eggs to knots

Easily digested when digestive

organs are reduced High in fat and protein Stopover at Delaware Bay is

synchronized to HSC spawning. Overharvesting has significantly

contributed to C. c. rufa decline.

Horseshoe Crabs (Limulus polyphemus)



Importance of Delaware Bay Utilized by 80% of North American Knot population

No suitable stopovers between DE Bay and breedinggrounds in Arctic

When eggs were overabundant, late-arriving knots couldstill reach a healthy departure weight.

In recent years, shortage of eggs slows weight gain in latebirds, reducing survival.

Declines in wintering numbers from staging populationssuggest high mortality during migration due to poorbody condition upon departure from DE Bay.

Poor health in part limits reproductive success.



Foraging on Delaware Bay

Knots show a Type II functional response to prey density.



Cross-species Comparison

Semipalmated Sandpipers,Sanderlings (left)

Use Delaware Bay as a crucialstopover

Show population declines

Implications of importance of Delaware Bay to shorebirds whostage there during migration.

Hudsonian Godwits (right) Share wintering grounds with

C. c. rufa in TDF

Do not stop at Delaware Bay

Show stable populationdemographics



Life Table: 1995-1998 survival rates

(Baker, et al., 2004)



Life Table: 5% decline in 1995-1998 rates




Life Table: 1998-2001 survival rates




Demography Models

Adult Survival = 85% Juvenile Survival = ½ adultNest success = 75% (3/4 eggs)

Best Case: 1995-1998

Compromised Adult Survival





Demography Models (cont’d)

Pending Extinction: 1999-2000





Comparison of Demography Models (Baker et al. 2004)

95% ConfidenceInterval

95% ConfidenceInterval

Annual adultsurvival = 85%

Annual adultsurvival = 56%



Threats to Red Knot Population Before 1955, hunting accounted for majority of predation. Habitat Destruction

Dredging Coastal Development Oil pollution

Shortage of Resources Harvesting of HSCs in DE Bay

Harsh arctic winters yield food late Disturbance

Research efforts Beach use Dogs

Climate Change

Short term: advantageous because of lengthened Arctic summer Long term: disadvantageous because of decrease in tundra habitat needed for

breeding. Small population size

Since large numbers, and sometimes entire populations, winter and stage together,they are especially vulnerable to stochastic events.

Decreased genetic variability can lead to the accumulation of detrimental traits.



Conservation Status

NJ – Listed as threatened in 1999 US – Not listed Canada – Listed as endangered in 2007

Western Hemisphere Shorebird Reserve Network Protect habitat in Argentina, Brazil,

Peru, Suriname, Mexico, U.S., and Canada. Manage about 81 million hectares of habitat

Management of HSCs in DE Bay 2008 harvest moratoriums

Female crabs in Delaware All crabs in New Jersey All harvesting is prohibited during spawning (May 1-June 7)

Shorebird Steward Program Volunteers educate the public about how their use of the beach could disturb

important shorebird habitats. Beginning in 2003, beaches in DE Bay used by migratory bird populations have

been closed to the pubic during staging. Since C. c. rufa is threatened in NJ, conservation officers can cite beachgoers for

disturbance and trespassing.



Literature Cited

2006. Magnificent Shorebird Migration. Prince William Network.http://migration.pwnet.org/pdf/Magnificent_Shorebird_Migration.pdf

Baker, Allen J, et al. 2004. Rapid population decline in red knots: fitness consequences of decreased refuelingrates and late arrival in Delaware Bay. Royal Society. 271, 875–882

Battley, Phil, et al. 2000. Empirical evidence for differential organ reductions during trans-oceanic bird flight.The Royal Society. 276: 191-195.

Boyd, Hugh, Theunis Piersma. 2001. Changing balance between survival and recruitment explains population

trends in red knots Calidris canutus islandica wintering in Britain, 1969-1995. ARDEA. 89: 301-317. Brown, S., et al. 2000. National Shorebird Conservation Assessment: Shorebird Conservation Status,

Conservation Units, Population Estimates, Population Targets, and Species Prioritization. Manomet Center forConservation Sciences. http://www.Manomet.org/USSCP/files.htm

Buehler Deborah M., A. J. Baker. 2005. Population Divergence Times and Historical Demography in Red Knotsand Dunlins. Condor . 107: 497-513.

Cornell Lab of Ornithology. 2009. All About Birds. Cornell University.

http://www.allaboutbirds.org/guide/Red_Knot/lifehistory Gilg, Olivier, Nigel Yoccoz. 2010. Explaining Bird Migration. Science. 327:276-8.

Gillings, S, et al . 2007. Shorebird predation of horseshoe crab eggs in Delaware Bay: species contrasts andavailability constraints. Journal of Animal Ecology. 76: 503–514.

Greenberg, Russel. 2005. Birds of Two Worlds. Johns Hopkins University Press. Baltimore. 263-5.

Harrington, Brian . 2001. The Birds of North America. Cornell Lab of Ornithology.http://bna.birds.cornell.edu/bna/species/563/articles/introduction

Hernandez, Daniel. Ornithology Lecture. Spring 2010.

http://www.manomet.org/USSCP/files.htm

http://www.allaboutbirds.org/guide/Red_Knot/lifehistory

http://bna.birds.cornell.edu/bna/species/563/articles/introduction

http://bna.birds.cornell.edu/bna/species/563/articles/introduction

http://www.allaboutbirds.org/guide/Red_Knot/lifehistory

http://www.manomet.org/USSCP/files.htm



Literature Cited Landys, Meta, et al . 2005. Metabolic profile of long-distance flight and stopover in a shorebird. The

Royal Society. 272: 295-301. McKinnon, L., et al . 2010. Lower Predation Rates for Migratory Birds at High Latitudes. Science.

327:326-7.

Morrison, Guy, R.K. Ross, L. Niles. 2004. Declines in Wintering Populations of Red Knots in SouthernSouth America. Condor . 106: 60-70.

Niles, Lawrence et al. 2008. Status of the Red Knot (Calidris Canutus) in the Western Hemisphere.

Studies in Avain Biology. 36:1-185. Niles, Lawrence et al. 2009. Effects of Horseshoe Crab Harvest in Delaware Bay on Red Knots: Are

Harvest Restrictions Working? Bioscience. 59: 153-164.

Piersma, Theunis et al. 1998. A new pressure sensory mechanism for prey detection in birds: the useof principles of seabed dynamics? The Royal Society. 265: 1377-1383.

Reneerkens, Jeroen, et al. 2005. Switch to diester preen waxes may reduce avian nest predation by mammalian predators using olfactory cues. The Journal of Experimental Biology. 208: 4199-4202.

Sibley, David. 2001. Bird Life and Behavior. Andrew Stewart. New York. 15-50, 273-287.

Shorebird Phenomenon. Manomet Center for Conservation Sciences.http://www.shorebirdworld.org/template.php?g=5&c=4

Van Gils, Jan et al. 2005. Reinterpretation of gizzard sizes of red knots world-wide emphasizesoverriding importance of prey quality at migratory stopover sites. The Royal Society. 272: 2609-2618.

Van Gils, Jan et al. 2006. Foraging in a tidally structured environment by red knots (Calidris canutus):

Id l b t t f E l 8 8

Documents

Appendix V.Population Biology: Red Knot Final Presentation