abstracts of oral and poster presentations - Pacific Seabird Group

(e.g., marine vs. freshwater) from stable carbon and nitrogen isotope analyses. Evidence for terrestrial molt in
female King Eiders was previously unsubstantiated.
RESTORATION OF REGIONAL TERN POPULATIONS: A MODEL FROM THE GULF OF MAINE
Stephen W. Kress (skress@audubon.org) and C. Scott Hall; Seabird Restoration Program, National Audubon
Society, Ithaca, NY USA
Populations of Common, Arctic, and Roseate terns in the Gulf of Maine were in decline during much of
the 20th Century and reached historic lows by 1977. Prior to 1984, few sites were actively managed for terns.
The restoration of one historic tern colony at Eastern Egg Rock proved that the combination of predator and
vegetation management and social attraction was an effective method for establishing new colonies. However,
the benefits of restoring a single colony proved to be limited over time due to the potential for catastrophic
events, especially predation by Herring and Great Black-backed gulls, Great-Horned Owls, Black-crowned
Night-Herons, and mink that occasionally impact nesting success. In 1984, seabird biologists from throughout
the Gulf of Maine adopted multiple-site management as the preferred method for attaining regional population
growth. Since 1984, ten historic tern colonies have been restored, and four additional sites are actively managed
for terns. In 2004, although Common, Arctic, and Roseate terns nested at a minimum of 47 sites, 98% of Arctic
Terns, 88% of Common Terns, and 93% of Roseate Terns nested at managed sites. Despite continued predator
problems, tern numbers remain stable or continue to increase within the region, as terns can move to alternate
sites to avoid predation. This twenty-year-old program demonstrates the benefits of a regional approach to tern
management.
SUPERNORMAL CLUTCHES (SNCs) IN RELATION TO INTRA-SPECIFIC NEST PARASITISM IN
BLACK-TAILED GULLS
Young-Soo Kwon (yskwon@khu.ac.kr), Who-Seung Lee, and Jeong-Chil Yoo; Korea Institute of Ornithology,
Kyung-Hee University, Seoul SOUTH KOREA
A supernormal clutch (SNC) refers to a nest with an unusually large clutch. This term has been applied
mostly to seabirds that typically lay three-egg clutches. We examined Black-tailed Gull (Larus crassirostris)
nests with abnormally large numbers of eggs during the 1997 and 2000–2002 breeding seasons at Hong-do
Island, South Korea. SNCs were found in 20 (2.49%) of 802 nests examined during 3 breeding seasons: 3 in
1997, 3 in 2000, and 14 in 2002 at Hong-do Island. Many studies suggest that occurrence of SNCs usually
results from female pairings or polygynous associations in Laridae. However, female–female pairing and
polygynous associations were not observed in Black-tailed Gulls nesting at Hong-do Island. We suggest that
adults rolled dropped strange eggs into their nests. The dropped strange eggs may be parasitized ones. If host
gulls find eggs laid by other gulls near the nest, they are likely to roll it into their nests. SNCs observed in
Black-tailed Gull nests appeared to be a type of intra-specific nest parasitism. We compared the reproductive
success of parasitized with non-parasitized clutches. In addition, we compared detected parasitic with nonparasitic
eggs within a clutch. Hatching efficiency of parasite eggs was lower than that of host eggs in a
parasitized nest. Fledging success and hatching success was highest in c/2; c/4 and c/5 had the lowest success.
Results imply that productivity of parasitized nests were lower than success of non-parasitized nests. If parasitic
nests increase, the breeding population may decrease.
EFFECT OF DATE OF BREEDING ON BREEDING SUCCESS IN BLACK-TAILED GULLS: MEANING
OF ARRIVAL BEHAVIOUR (COLONIAL MOBBING) [Poster]
Young-Soo Kwon (yskwon@khu.ac.kr), Who-Seung Lee, and Jeong-Chil Yoo; Korea Institute of Ornithology,
Kyung-Hee University, Seoul SOUTH KOREA
In this study, we investigated the nest timing and breeding success of Black-tailed Gulls (Larus
crassirostris) in relation to initial arrival behaviour (colonial mobbing) after early return on their breeding
ground. Investigations of initial arrival behaviour of Black-tailed Gulls were carried out from 7 April to 13
April in 2003. Black-tailed Gulls that arrived at the breeding ground did not remain on their territory. Instead,
they fed to accumulate energy for breeding. As the egg-laying period approached, they gradually increased time
spent on the territory. During the breeding season, time spent at the nest was highest on 22 April, when adults