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Anti-predator Responses of the Black-tailed Gull (Larus crassirostris) Flock to Mobbing and Mew Call PlaybacksKeywords: Avian communication , Black-tailed gull , Larus crassirostris , Mobbing call Abstract: We studied the functional roles of two types of calls, mew calls and mobbing calls, of the blacktailedgull (Larus crassirostris) by examining responses of mixed flocks of gulls to the playback calls. Playbackexperiments were conducted on four days between 11 May and 5 June 2007 at 16 sites in Sinjindo-ri andDowhang-ri, Taean-gun, Chungnam province and Imjado, Sinan-gun, Jeonnam province, South Korea. Weexamined the anti-predator responses of the gulls to the playback trials. We found that gull flocks initiallyresponded to mew call playbacks by mobbing in less than half of playback trials (6/14) while all trials involvingplaybacks of the mobbing call and control (group mobbing) call evoked mobbing. When trials in which noresponse was recorded were excluded, we found that the gulls’ responses to mobbing and group mobbing callplaybacks was more intense than their response to mew call playbacks, in that gulls mobbed longer, more gullsresponded, and gulls took flight after a shorter time interval. However, the intensity of the gulls’ response didnot differ in mobbing call and group mobbing call playbacks. The results of this study suggest that themixed-species flocks of gulls discriminate between the mew calls and the mobbing calls.
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