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Behav Ecol Soc 56(1)

Subject: Behav Ecol Soc 56(1)
From: Jerome SUEUR <>
Date: Thu, 22 Apr 2004 13:39:51 -0700
<tt>Sharon A. Gill, Spencer G. Sealy, 2004</tt><br>
 <tt>Functional reference in an alarm signal given during nest defence: seet 
 calls of yellow warblers denote brood-parasitic brown-headed cowbirds</tt><br>
 <tt>Behavioral Ecology and Sociobiology,56(1): 71-80.</tt><br>
 <tt>Abstract  Field observations and model-presentation experiments have shown 
 that yellow warblers (Dendroica petechia) produce seet calls preferentially 
 in response to brood-parasitic brown-headed cowbirds (Molothrus ater). In 
 this study, we investigated whether seet calls are functionally referential 
 alarm calls denoting cowbirds by determining whether female warblers 
 responded appropriately to seet calls in the absence of a cowbird, whether 
 alarm calling by warblers varied with response urgency, and how warblers in 
 a population allopatric with cowbirds responded to cowbird and avian 
 predator models and seet playbacks. As a control, we presented chip calls, 
 which are elicited by nest predators as well as by non-threatening 
 intruders, but are not strongly associated with cowbirds. Yellow warblers 
 responded differently to playbacks of seet than chip calls. To seet 
 playbacks, almost 60% of females gave seet calls and rushed to sit in their 
 nests, responses typically elicited by cowbirds, whereas these responses 
 were given infrequently in response to chip calls. Yellow warblers seet 
 called equally in situations that simulated low, medium and high risk of 
 parasitism, which suggests that these calls did not vary with response 
 urgency. In a population allopatric with cowbirds, seet calls were rarely 
 produced in response to cowbird or avian nest predator models and never to 
 seet playbacks. These results suggest that seet calls are functionally 
 referential signals denoting cowbirds and that cowbird parasitism was a 
 strong selective pressure in the evolution of functional referentiality in 
 the seet call of yellow warblers.</tt><br>

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