Intraspecific and interspecific vocal variation in three Neotropical cardinalids (Passeriformes:Fringillidae) and its relationship with body mass

Abstract

The negative relationship between song frequencies and body weight found by Wallschläger in 1980 is well supported by several studies considering a large number of bird species. However, the results obtained when comparing closely related species or at the intra-specific level were contradicting. The present study compares the vocalizations of four closely related species of Neotropical cardinalids, considering their subspecies: Cyanoloxia glaucocaerulea, Cyanocompsa parellina, Cyanocompsa brissonii and Cyanocompsa cyanoides. These species and subspecies differ significantly in their body mass and provide the opportunity to test the hypothesis that heavier groups produce songs with lower frequencies in closely related lineages. We found that emphasized frequency shows a negative correlation with body weight. These results provide support to Wallschläger´s hypothesis both at the intra- and inter-specific levels in members of the Cyanoloxia-Cyanocompsa clade. Note length, note rate and internote interval length also correlated with body mass, the heavier species having longer notes produced at a lower rate and separated by longer intervals. This correlation of temporal variables with body mass suggests that body size could also influence the temporal structure of song.