Meeting Abstract
Species’ vocalizations are often tuned to the acoustic features of their habitats to facilitate effective communication. We investigated the relationship between spectral characteristics of calls and habitat noise in some species of Andean hummingbirds which produce high-frequency vocalizations and live in cloud forest and high-altitude grasslands. We tested the hypothesis that high-frequency vocalizations represent adaptations to avoid signal masking generated by ambient noise. The Buff-tailed coronet (Boissonneaua flavescens), Speckled hummingbird (Adelomyia melanogenys), and Violet-tailed sylph (Aglaiocercus coelestis) live in the cloud forest and produce vocalizations with high frequencies (FF=9.046 kHz, FF=10.716 kHz, and FF=11.935 kHz, respectively), compared to other hummingbirds. Environmental noise there occurs in a frequency range between 3-9 kHz in which most other birds sing, and another range from 12.5-15 kHz generated mostly by insects. This suggests that these cloud-forest hummingbirds vocalize at high frequencies to benefit from a ‘noise-free’ window in their environmental acoustics. Meanwhile, the Ecuadorian Hillstar (Oreotrochilus chimborazo) lives in high-altitude grasslands and produces a song with even higher frequencies (FF=14.189 kHz); in this habitat, however, the ambient noise, typically generated by wind, occurs largely below 5 kHz. Our findings suggest that avoidance of signal masking may contribute to the presence of high-frequency vocalizations in the cloud-forest hummingbird species, while other factors may account for the occurrence of the very high-frequency song in the Hillstar.
