of the NY Harbor 2010 Harbor Herons and Waterbirds Susan Elbin New York City Audubon Liz Craig New York City Audubon and Cornell University Cormorants Year 2005 2006 2007 2008 2009 ID: 796791
Download The PPT/PDF document "Double-crested Cormorants" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Double-crested Cormorants
of the NY Harbor2010 Harbor Herons and Waterbirds …
Susan Elbin , New York City Audubon
Liz Craig, New York City Audubon and Cornell University
Slide2Cormorants
Slide3Year
2005200620072008
2009
2010
Nests
906
1175
1046138412181411Islands667778Banded0198240225255201
Double-crested Cormorant
Birds Banded in the NY Harbor
Slide4Slide5Slide6Slide7Gulls in Jamaica Bay
2010 Update
Dr. Brian E. Washburn
USDA, APHIS, Wildlife Services,
National Wildlife Research Center
419-625-0242
brian.e.washburn@aphis.usda.gov
Slide8Slide9Research Objective
Estimate the size of gull nesting populations in the Jamaica Bay Unit of Gateway NRA
Slide10Jamaica 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
Slide11Count 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
Slide12Count 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
Slide13JFKIA
HERG
Slide14JFKIA
GBBG
Slide15JFKIA
LAGU
Slide16Research Objective
Estimate the population of laughing gull nests in Jamaica Bay
Slide17Aerial Photography Approach
Slide18No estimate
Number of LAGU Nests
No estimate
Slide19Joco 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
Slide20Slide21Diet of Double-crested Cormorants in NY Harbor, 2010 update
Colin Grubel, CUNY Graduate Center & Queens CollegeJohn Waldman, Queens College
Slide22Colony comparisons
South Brother4 collection trips83 items identified15 sp. fish, 1 crustaceanMost common sp: Hogchokers (24%) & goldfish (22%)
Swinburne
2 collection trips
72 items identified
18 sp. fish, 1 crustacean
Most common sp: spotted hakes (29%)
Slide23Conclusions
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
Slide24Investigations into the Factors Affecting Pellet Production
Slide25Introduction
Diet studies are an important part of managementBoli & pellets most common methods of diet assessmentBoli (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
Slide26Feeding Trials
Prey spininessOtolith morphologyPrey 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
Slide27Prey Spininess
Hypothesized that spines present on some species of fish may irritate the gutWould speed up pellet productionLess 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–spiny95% of fish identified in pellets were spiny, 5% were non-spiny
Slide28Otolith Morphologies
Compact otolithsCroakerScadPinfishgoldfishFragile otolithsThreadfin 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*
Slide29Conclusions
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 unknownProcess may be different in wild birdsOtolith shape can affect the likelyhood of surviving to be ejected and identified in a pelletOtolith size may also be important but more research needed