REPRODUCTIVE BEHAVIOR AND COMMUNICATION IN BLUE-THROATED HUMMINGBIRDS

Abstract

Previous studies of Blue-throated Hummingbirds (Lampornis clemenciae) showed that males have elaborate songs and females also sing. Here we report complex territorial systems, sexual behavior, and communicatory repertoires of both sexes. Males typically defended territories along streams throughout the reproductive season. Time budgets revealed that males allocated more time to vocalizing in territorial advertisement than in more energetically costly activities such as chases. Both observations and playback experiments indicated that two vocalizations have different roles in territorial advertisement. Strings of chips served in long distance territorial advertisement, while the lower amplitude song, more prevalent early in the season, attracted females and also repelled males from the immediate area. Agonistic interactions included long chases, some with vocalizations. During close range encounters an array of postures and sounds occurred. Females defended territories against other females during a brief period preceding egg laying. Sexual interactions were unusually intricate, consisting of a series of activities in which the female played an active role. She delivered loud calls advertising sexual readiness and performed aerial displays. Males competed with other males for access to females. We observed four presumed copulations, all preceded by a song fragment from the male. The vocal repertoire included at least 16 different sounds, all with different functions, an unusually large number for a nonoscine. Male songs were the most complex sounds. Behaviors that differed from many other hummingbirds that have been studied included strong reliance on vocal signals, lack of male aerial displays, and female advertisement of sexual readiness. These attributes may be linked to reduced sexual dichromatism and related to the species' preference for wooded riparian habitats.