RESUMEN
In many tropical animals, male and female breeding partners combine their songs to produce vocal duets [1-5]. Duets are often so highly coordinated that human listeners mistake them for the songs of a single animal [6]. Behavioral ecologists rank duets among the most complex vocal performances in the animal kingdom [7, 8]. Despite much research, the evolutionary significance of duets remains elusive [9], in part because many duetting animals live in tropical habitats where dense vegetation makes behavioral observation difficult or impossible. Here, we evaluate the duetting behavior of rufous-and-white wrens (Thryothorus rufalbus) in the humid forests of Costa Rica. We employ two innovative technical approaches to study duetting behavior: an eight-microphone acoustic location system capable of triangulating animals' positions on the basis of recordings of their vocalizations [10] and dual-speaker playback capable of simulating duets in a spatially realistic manner [11]. Our analyses provide the first detailed spatial information on duetting in both a natural context and during confrontations with rivals. We demonstrate that birds perform duets across highly variable distances, that birds approach their partner after performing duets, and that duets of rivals induce aggressive, sex-specific responses. We conclude that duets serve distinct functions in aggressive and nonaggressive contexts.
Asunto(s)
Pájaros Cantores/fisiología , Vocalización Animal , Estimulación Acústica , Acústica , Animales , Costa Rica , Ecosistema , Femenino , Masculino , ApareamientoRESUMEN
A field test was conducted on the accuracy of an eight-microphone acoustic location system designed to triangulate the position of duetting rufous-and-white wrens (Thryothorus rufalbus) in Costa Rica's humid evergreen forest. Eight microphones were set up in the breeding territories of 20 pairs of wrens, with an average intermicrophone distance of 75.2+/-2.6 m. The array of microphones was used to record antiphonal duets broadcast through stereo loudspeakers. The positions of the loudspeakers were then estimated by evaluating the delay with which the eight microphones recorded the broadcast sounds. Position estimates were compared to coordinates surveyed with a global-positioning system (GPS). The acoustic location system estimated the position of loudspeakers with an error of 2.82+/-0.26 m and calculated the distance between the "male" and "female" loudspeakers with an error of 2.12+/-0.42 m. Given the large range of distances between duetting birds, this relatively low level of error demonstrates that the acoustic location system is a useful tool for studying avian duets. Location error was influenced partly by the difficulties inherent in collecting high accuracy GPS coordinates of microphone positions underneath a lush tropical canopy and partly by the complicating influence of irregular topography and thick vegetation on sound transmission.