Relationships of song structure to phylogenetic history, habitat, and morphology in the vireos, greenlets, and allies (Passeriformes: Vireonidae)

Acoustic signals show immense variation among passerines, and several
hypotheses have been proposed to explain this diversity. In this study, we
tested, for the first time, the relationships of song structure to
phylogeny, habitat type, and morphology in the vireos and allies
(Vireonidae). Every measure of song structure considered in this study had
moderate and significant phylogenetic signal. Furthermore, two
song-constraining morphological traits, bill shape and body mass, also
exhibited significant phylogenetic signal. Song length showed the largest
within-clade similarity; longer songs were highly conserved in part of the
greenlet (Hylophilus) clade, whereas shorter songs characterized the
remaining seven genera. We found no differences in song structure among
vireonids living in different habitat types. However, vireonids with
shorter, stouter bills and larger bodies sang songs with lower minimum and
maximum peak frequency, compared with species with longer, thinner bills
and smaller bodies. We conclude that Vireonidae song evolution is driven
partially by phylogenetically conserved morphological traits. Our findings
support the phylogenetic signal and morphological constraints hypotheses
explaining structural diversity in avian acoustic signals.