abstracts of oral and poster presentations - Pacific Seabird Group

WHY SEABIRD COLONIES FORM RELUCTANTLY BUT GROW RAPIDLY
Dean Kildaw 1 (ffdsk@uaf.edu), C. Loren Buck 1 , and David B. Irons 2 ; 1 School of Fisheries and Ocean Sciences,
University of Alaska, Fairbanks, AK USA; 2 USFWS, Migratory Bird Management, Anchorage, AK USA
Observations from the few empirical and theoretical studies that have addressed patterns of formation
and growth of seabird colonies are paradoxical: prospective breeders are highly attracted to newly-formed
colonies, yet they will compete for nest sites within established colonies and face the prospect of deferred
breeding, rather than pioneer unoccupied habitat and form a new colony. The "information barrier" hypothesis
of Forbes and Kiaser explains the attraction of established colonies by suggesting that conspecifics represent a
valuable information resource concerning habitat suitability that mitigates costs of joining a colony. We
investigated the formation and growth of Black-legged Kittiwake (Rissa tridactyla) colonies using productivity
and population data from 14 colonies that formed during the late 1980s within Chiniak Bay, on Kodiak Island,
Alaska. New colonies formed during a period of poor productivity and population declines within established
colonies. They exhibited greater productivity than established colonies and displayed extremely rapid growth
fueled by mass immigration for at least a decade. We propose that the information advantage is just one of
many factors that contribute to the "Allee effect" (inverse density dependence) in young seabird colonies. We
further suggest that timing of formation and rapid growth observed for new colonies in Chiniak Bay is best
explained by merging Fretwell's classic "ideal despotic" and "Allee" habitat suitability models.
DIET OF AMERICAN WHITE PELICANS WINTERING IN LOUISIANA AND MISSISSIPPI
D. Tommy King (Tommy.King@aphis.usda.gov), J. Brent Harrel, James F. Glahn, and Scott C. Barras;
USDA/WS National Wildlife Research Center, Mississippi State University, Mississippi State, MS USA
The number of American White Pelicans (Pelecanus erythrorhynchos) wintering in the aquaculture
production areas of the southeastern United States has increased dramatically. No published studies have
reported on the diet of American White Pelicans wintering in this area. We collected 198 pelicans from loafing
sites during winter and spring (1998–1999) at four locations in Mississippi and four in Louisiana. Mississippi
collection sites were near aquaculture facilities (AQMS), and the Mississippi River and an oxbow lake adjacent
to the river (RVMS). Louisiana collection sites were near aquaculture facilities (AQLA) and marsh habitat of
coastal Louisiana (COLA). We identified, measured, and weighed all prey items found in pelican digestive
tracts. Teleost otoliths were retained for fish prey identification to help determine species composition. Otoliths
were identified to family and genus, when possible. The percent of otoliths by family group from stomachs of
pelicans (N = 134) collected near (1) AQMS was 87.6% catfish, 8.5% shad, 4.0% other; (2) RVMS was 29.7%
catfish, 58.6% shad, 6.3% sunfish, 5.4% other; (3) AQLA was 0.5% catfish, 63.3% shad, 27.6% sunfish, 8.3%
other; (4) COLA was 7.4% shad, 12.8% sunfish, 19.8% mullet, 13.9% other, and 46.1% unknown. We found
that American White Pelicans in Louisiana and Mississippi feed on native and aquaculture species typically
occurring near their loafing sites.
NEW INSIGHTS INTO THE MOLT MIGRATION OF FEMALE KING EIDERS FROM STABLE CARBON-
AND NITROGEN-ISOTOPE ANALYSES
Michael Knoche* (ftmjk1@uaf.edu); U.S.G.S. Alaska Cooperative Fish and Wildlife Research Unit,
Department of Biology and Wildlife, University of Alaska, Fairbanks, AK USA
Female King Eiders are expected to demonstrate diverse patterns of wing molt relative to males because
timing and location of molt are closely linked to breeding. We examined the stable carbon and nitrogen isotope
values of primary feathers from female King Eiders during breeding on Alaska’s North Slope and spring and
molt migrations at Pt. Barrow, Alaska, in 2003. Additionally, we collected primary feathers from females
implanted with satellite transmitters in 2003 and 2004. We found heavy stable carbon and nitrogen isotope
values of primary feathers from 94% of the females, demonstrating that protein sources were derived from
mixed aquatic and marine systems. However, 6% of females had significantly lower nitrogen-isotope values
from feathers (n = 96, P < 0.0001) that coincided with the lightest stable carbon-isotope values in the carbon
isotope range and were thought to indicate terrestrial molt in this group. We found no relationship between
known geographic location of wing molt and stable isotope values of feathers from transmittered females. We
concluded that we can infer relative proportions of female King Eiders molting in isotopically distinct regions