Vocal distinctiveness between two populations of Giant Antshrike (Batara cinerea)

Variation in the mating signals emitted by birds may have a significant impact on species evolution. If vocal divergence is related to isolation between populations, the species may be undergoing to a process of speciation. Vocal variation in Suboscine birds like Giant Antshrike may be associated with selective adaptation, since it cannot be attributed to learning deviation in this group. Environmental conditions may be determinant on the selection of vocal features because sound transmission is enhanced under certain conditions of temperature, humidity and vegetal cover. Therefore, we examined vocalizations of Giant Antshike and searched for possible acoustic variations between two disjunct populations (Andean and Atlantic), correlating the differences to environmental structure. We measured temporal and spectral features form 80 individuals. Univariate and multivariate analysis displayed differences between both populations. Andean individuals produce vocalizations with more syllables, higher trill rate and pace, and higher values of frequencies, but with short syllable length. Environment exerts significant effects on acoustic structure, since it is related to temperature variation, precipitation, latitude and elevation, but not to vegetal cover. Since the vegetal structure of environment do not have influence on the pattern of variation, we argue that vocal distinctiveness between populations arise from habitat divergence, which influences morphology of individuals. Therefore, vocal variation seems to be a by-product of morphological adaptation to different conditions of habitat.