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Individual differences in nest defense in the colonial breeding Black-tailed Gulls

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Title: Individual differences in nest defense in the colonial breeding Black-tailed Gulls
Authors: Kazama, Kentaro Browse this author
Watanuki, Yutaka Browse this author →KAKEN DB
Keywords: Aggressiveness
Black-tailed Gull
Group living
Nest defense
Issue Date: Aug-2010
Publisher: Springer Berlin / Heidelberg
Journal Title: Behavioral Ecology and Sociobiology
Volume: 64
Issue: 8
Start Page: 1239
End Page: 1246
Publisher DOI: 10.1007/s00265-010-0938-8
Abstract: Often in colonial seabirds, all colony members are believed to defend against nest predators and experience equal nest predation risk. However, the variation of defense behavior among members and its reproductive consequences are largely unknown. We investigated 1) individual variation in the nest defense of breeding Black-tailed Gulls Larus crassirostris against a natural egg predator, the Jungle Crow Corvus macrorhynchos and 2) how this behavioral variation affects an individual's own nest predation risk and that of their neighbors. Results were compared between two years where crow attack levels were manipulated to average 5 and 22 times normal rates ("low" and "high" predation risk years, respectively) by the placement of varying numbers of artificial nests containing unguarded eggs at the perimeter of the gull colony. In both years, 23-38% of parents, mostly males, showed "aggressive" defense behavior (strikes or chases) against crows and decoys. Other "non-aggressive" gulls showed no defense. In the year of low predation risk, intrusion rates by crows (landing within 0.5 m of an individual gull's nest) were similar for aggressive and non-aggressive gulls. In the year of high predation risk, however, the rates of intrusion for aggressive gulls (4%) and for non-aggressive gulls with an aggressive neighbor (37%) were significantly lower than for non-aggressive gulls without an aggressive neighbor (76%). These results indicate that aggressive individuals reduce nest predation risk for themselves and conspecific neighbors in a colonially breeding species.
Rights: The original publication is available at
Type: article (author version)
Appears in Collections:水産科学院・水産科学研究院 (Graduate School of Fisheries Sciences / Faculty of Fisheries Sciences) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 風間 健太郎

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