EFFECTS OF COLONIALITY ON GULL PREDATION ON COMMON TERN (STERNA-HIRUNDO) CHICKS

Authors
Citation
Ph. Becker, EFFECTS OF COLONIALITY ON GULL PREDATION ON COMMON TERN (STERNA-HIRUNDO) CHICKS, Colonial waterbirds, 18(1), 1995, pp. 11-22
Citations number
NO
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Ecology,Ornithology
Journal title
ISSN journal
0738-6028
Volume
18
Issue
1
Year of publication
1995
Pages
11 - 22
Database
ISI
SICI code
0738-6028(1995)18:1<11:EOCOGP>2.0.ZU;2-3
Abstract
On the Wadden Sea island of Mellum, I studied the relationship of colo niality (nearest neighbor distance during clutch initiation, nest dens ity, centrality) with chick loss through. predators and with breeding success in Common Terns from 1980 to 1982. One hundred fifty pairs wer e breeding adjacent to a Herring Gull colony (10,000 pairs). Nest dens ity decreased over the years. Fledging success varied between 0-19%, b ecause annual losses to predators, mainly Herring Gulls, were between 44-94% of the chicks. More than 50% of the chicks taken were less than or equal to 5 d old; up to this age they were found in 92% of cases l ess than or equal to 5 m away from the nest. For clutches initiated la ter in the season, nearest neighbor distance increased, nest density a nd centrality decreased. Except in 1982, significant positive correlat ions were found between the percentage of broods suffering chick losse s by predators and laying date and nearest neighbor distance; negative correlations were found with nest density and centrality. In 1980, ne st density was more crucial for chick survival than centrality, and th e total breeding success was also positively correlated with nest dens ity and centrality. In all years, the age of chicks at predation corre lated positively with nest density. The results are discussed with res pect to adaptive functions of coloniality such as predator swamping an d anti-predator behavior, which was more effective in colony-areas of high density. Coloniality was advantageous only for early, dense and c entral breeders, but not for the whole colony.