John L. Bower
Bioacoustics Research Program, Cornell Laboratory of Ornithology

Abstract

I used new array recording and analysis techniques to document the acoustic interactions of multiple Song Sparrows, Melospiza melodia, before and after territorial encounters. I conducted a calibration experiment that demonstrated that these acoustic techniques could be used to accurately estimate the locations of free ranging birds, confirming that these techniques can be useful tools in animal communication studies. Song Sparrows from the migratory population I studied used three strategies to gain a territory. Early in the breeding season, males settled undefended land (establishment strategy) or challenged an established male for possession of his territory (replacement strategy). Later, males defended a small area and then expanded the area by usurping portions of nearby territories (expansion strategy). Late in the season, males either used a replacement or expansion strategy. The intensity and duration of territorial conflicts differed depending on the intruding male's strategy. Males involved in territorial conflict did not appear to use song-type matching to direct song at each other during pre-encounter singing, possibly because in this migratory population Song Sparrows do not share enough songs to make song-type matching an effective means of communicating. Males who challenged for territories did not overlap the songs of defending males during pre-encounter singing. Defending males appeared to avoid overlapping the songs of challengers, possibly in an attempt to de-escalate the conflict. Males sang at high song rates prior to initiating encounters. Males who defended territories sang at lower, more variable song rates. Although pre-encounter song rates were not correlated with male fighting ability, it is possible that some other song feature exhibited during high song rate singing is correlated with fighting ability. Unpaired neighbors to the birds involved in encounters sang at higher pre-encounter song rates than unpaired non-neighbors. Birds who won encounters were the only neighborhood birds to significantly increase their song rates after an encounter ended. These findings are consistent with the hypothesis that a winner's post-encounter song rate may constitute a victory display.

Reprinted with permission:

John Lawrence Bower, 2000. Acoustic Interactions During Naturally Occurring Territorial Conflict in a Song Sparrow Neighborhood. Ph.D. thesis, Cornell University.