SONG CLUSTERING BY MEADOWLARKS: IS IT RELATED TO REPERTOIRE SIZE?

Abstract

AbstractSome birds with song repertoires sequentially associate (or cluster) songs of different types. That is, certain song types may occur together repeatedly, even on different days. We determined whether clustering of meadowlark songs correlated with repertoire size. We also tested whether clustered songs reflect either their structural similarities, or dissimilarities. Our data were obtained from recordings of free-living individuals of two meadowlark species, eastern, Sturnella magna , and western, S. neglecta . Eastern meadowlarks have approximately 10 times more song types per bird than do westerns. Therefore, if clustering is related to repertoire size, we predicted that there should be (1) proportionately more song clusters in eastern meadowlarks than in westerns, and (2) a similar correlation across individual birds within a species, especially so in easterns, which have a broader range of repertoire sizes. All 14 easterns examined showed clusters whereas only 5 of 11 westerns did so, and the easterns had proportionately more per bird. Many of the same clusters occurred in different recordings of individual easterns. In easterns, the extent of clustering as measured by a PCA analysis correlated strongly with estimated repertoire size. Clustered songs were neither more similar in structure, nor less so, than randomly-paired songs.