Intra and inter-specific vocal variation in three species of Grosbeaks (Passeriformes: Cardinalini) and its relationship with body mass.

NATALIA C. GARCÍA; ANA S. BARREIRA; CECILIA KOPUCHIAN; PABLO L. TUBARO

Vancouver

Congreso; V North American Ornithological Conference; 2012

The negative relationship between song frequencies and body size, first described in birds by Wallschläger in 1980, is well supported by several studies considering a large number of species, but contradicting results were obtained at the intraspecific level. Variation in temporal song traits, on the other side, has been related to the effect of the habitat acoustics on song communication. However, the rate at which notes are produced, particularly in songs that include trilled sequences, could also be related to morphological traits that usually correlate with body size, such as bill size. Here, we compared the vocalizations of Cyanoloxia glaucocaerulea, Cyanocompsa brissonii and Cyanocompsa cyanoides. Cyanoloxia glaucocaerulea and Cyanocompsa brissonii are sister species, and Cyanocompsa cyanoides is the sister species of this clade. Both Cyanocompsa species are divided into several subspecies, so they provide a good model to describe the variation in song traits in relation to body mass in closely related groups. We analyzed the songs of C. glaucocaerulea, all subspecies of C. cyanoides and four out of five subspecies of C. brissonii using the program Raven version 1.3. We measured frequency and time-related variables, and we collected weight data from specimens stored at different museums and also from bibliography. We evaluated the correlation between each song variable and the mean weight of each group. We found significant differences between and within species in both frequency and time-related variables, as well as in body mass. When comparing all the groups together we found that emphasized frequency shows a clear negative correlation with body mass. Note rate and internote interval length also significantly correlated with body mass, the heavier species having lower note rate and longer internote intervals. Even though the differences are small, our results suggest that the negative correlation between frequency and body size stands when comparing closely related groups, at least for the emphasized frequency. The correlation of note rate and internote interval length with body mass that we found suggests that body size could also influence the temporal structure of song, even in birds that do not use trills.