Meeting Abstract
When producing a signal, a sender faces environmental challenges that affect transmission and may prevent the intended receiver from detecting the signal. Therefore, animals produce signals that are adapted to habitat conditions, facilitating intraspecific communication. We assessed signal transmission of high-frequency vocalizations (8-15 kHz) from three species of Andean hummingbirds. Adelomyia melanogenys and Boissonneaua flavescens, which live in the cloud forest, produce simple high-frequency calls. In high-altitude grasslands, Oreotrochilus chimborazo produces longer, more complex high-frequency vocalizations. Playback recordings were collected at 1, 5, 10, 20, and 40 m from the speaker to measure signal attenuation and spectral degradation. Compared to O. chimborazo, calls of B. flavescens and A. melanogenys showed the highest sound levels at 1 m in both habitats, although slightly higher in the cloud forest than in the grasslands. O. chimborazo vocalizations were better transmitted at 1 m in their native grassland than in the cloud forest. This shows that each high-frequency vocalization transmits better in its habitat, at least at 1 m. At 5 m, vocalizations of all three species underwent substantial attenuation in both habitats, and they had comparable sound levels. At 20 m, amplitude in all calls was almost indistinguishable from background noise. At this distance, however, spectral fidelity was higher in the grasslands than in the cloud forest for vocalizations of the three species, confirming that high frequencies degrade less in open habitats. Altogether, these results suggest that high-frequency vocalizations in these hummingbirds may be employed in short-range communication rather than in long-distance signaling.
