Meeting Abstract
Hearing is often tuned to acoustic features in conspecific vocalizations. For example, in birds, most vocalizations are in a frequency range between 1- 6 kHz, with some reaching 9 kHz. The frequency sensitivity of most birds also falls within this range, considerably lower than that of many species of mammals. Here, however, we describe vocalizations from an Andean hummingbird that are well above the maximum frequency reported for other birds. The Ecuadorian Hillstar (Oreotrochilus chimborazo) is a hummingbird living in high-altitude ecosystems in the northern Andes. We recorded four individuals from different populations, finding in all of them high frequency vocalizations. The fundamental frequencies ranged across individuals from 10.72 ± 0.45 kHz (mean ± SEM) to 16.60 ± 0.64 kHz, and harmonics exceeded 28 kHz. The complexity of the vocalizations was reminiscent of song in other species of birds; they were tonal, rich in frequency modulations, and had a duration of 1.13 ± 0.13 sec, which is longer than that of regular calls in hillstars. We also observed that these vocalizations are stereotyped within individuals, although variations between individuals occur. Among the hillstars, only males seem to produce these vocalizations, typically while sitting atop perches as if overseeing their territories. Though other studies have reported high frequency vocalizations in birds, these were either transient or harmonics of much lower fundamental frequencies. Given the complexity of these vocalizations and the context in which they are produced, it is likely that they function as songs.
