Dissecting the roles of body size and beak morphology on song evolution in the "blue" cardinalids (Passeriformes: Cardinalidae)

TUBARO, PABLO L.; GARCÍA, NATALIA C.

AUK

AMER ORNITHOLOGISTS UNION

Año: 2018 vol. 135 p. 262 - 275

0004-8038

Certain vocal signals can be difficult or challenging to produce due to constraints on vocal mechanics. In the case of bird song, both body size and beak morphology have been shown to constrain spectral and temporal song parameters. Therefore, variation within a clade in both morphological traits could exert an important effect in vocal evolution and diversity. However, given the allometric relationships between body and beak size, it is not always easy to separate the effects they may have. Additionally, different habitats impose different sources of sound attenuation and degradation, and bird song seems to be adapted to minimize the sound degradation specific to their habitat. Here, we analyze vocal variation in relation to both body size and beak morphology in 13 out of 14 species in the ?blue? clade of Cardinalidae family, controlling for habitat characteristics. On the one hand, we found the predicted negative correlation of body size with song frequencies, but no effect on temporal variables. On the other hand, we found no relationship between different beak dimensions (corrected by body size) and song frequencies, but we found that beak length correlated negatively with note rate and a positively with the duration of the interval between notes. Similar results have been found previously, but mostly in species with trilled songs, where notes are equal and produced at a constant rate. Our results show that different morphological variables, even if strongly correlated, can exert differential constrains in a complex behavioral trait such as song. A better understanding of the relevance of these proximate factors in shaping vocal evolution is fundamental to understand the causes of avian vocal diversity.