Phylogenetic and ecological effects on interspecific variation in structurally simple avian vocalizations

Flight calls are structurally simple avian vocalizations largely associated with sustained migratory flight. We used a multilocus phylogeny of 47 North American wood warblers (Aves: Parulidae) to quantify the extent of phylogenetic signal in flight-call spectrographic characteristics and to remove phylogenetic effects when testing for associations among flight-call attributes, behavioural characters related to migration strategies and ecological habitat variables. We also employed a quantile regression and null model approach to compare a matrix of interspecific phylogenetic divergence with indices of the corresponding acoustic differences derived from spectrographic measurements of flight calls. Nearly half of the measurements of flight-call properties exhibited significant associations with phylogeny. Controlling for phylogenetic effects, high-frequency flight calls were associated with species occupying taller and more open forest canopies. Ecological properties associated with migratory and winter distributions did not correlate with flight-call characteristics. Differences among the evolutionary histories of structural vs. signal properties of flightcalls suggest that phylogenetic and ecological effects are present. The evolution of flight-call syllable structure may involve selection for species recognition, whereas adaptation to the acoustic environment likely has influenced evolution of their spectral and temporal properties. More generally, the historical contribution to variation in behavioural characters is a long-standing source of debate; these results suggest that substantial phylogenetic effects may be present even in vocal traits that may be highly labile. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 155–173.