Document: PAI-3-53-9

Patterns of song variation in different seasons in the bronzed cowbird support different evolutionary hypotheses.

WARREN, P.*

University of Texas at Austin, Austin, TX 78712, USA ¹

Abstract:
Many species of migratory birds continue to sing after the breeding season is over and even on their wintering grounds. Little is known about the function of song during the non-breeding season, but some species have been known to respond to playbacks of songs heard in the winter. However, no systematic study of variation in responses to different wintering songs has been conducted. I studied large scale patterns of song variation in the Bronzed Cowbird (Molothrus aeneus). I discovered differing patterns of song dialect variation in the breeding season versus the wintering season. These differing patterns also support different hypotheses for the origin and evolution of song dialects. I also tested the responses of breeding male Bronzed Cowbirds to four song dialects recorded on wintering grounds in the Mexico and the United States. The birds appeared to respond most strongly to a song dialect which might only be heard on their wintering grounds. Despite its status as an invasive brood parasite, few studies have examined the behavior of the Bronzed Cowbird. The wintering behavior of this species suggests possibilities for controlling this potentially destructive species.

Keywords: cowbirds, seasonal differences, song variation

This abstract is being presented at: 12:00 PM in session:
Oral Session #3: Avian Ecology.