double-crested cormorants of the ny harbor 2010 harbor herons and waterbirds … susan elbin, new...
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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 2010
Nests 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
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Gulls in Jamaica Bay 2010 Update
Dr. Brian E. Washburn
USDA, APHIS, Wildlife Services, National Wildlife Research Center
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
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E. Joco Island
Silver Hole
E. H. Meadow
JocoN
o es
tim
ate
Nu
mb
er o
f L
AG
U N
ests
No
esti
mat
e
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