Meeting Abstract

55.5  Jan. 6  How hummingbirds choose their fights: the role of iridescent coloration in aggressive interactions. MEADOWS, M. G.*; MCGRAW, K. J.; Arizona State University, Tempe melissa.meadows@asu.edu

Pigmentary feather color in birds has been widely studied as an honest signal of individual quality that can used by conspecifics in mate choice and other social interactions. However, the signaling role of structural color, including iridescence, is less well-known, particularly in intrasexual competitions. In birds, this type of status signaling has only been studied twice (in blue tits and collared flycatchers), and has never been studied in a species with iridescent structural colors. Here, we examine the use of iridescent gorget color and size as potential signals in aggressive interactions in male Anna�s hummingbirds (Calypte anna). Two separate experiments were conducted in which individual birds were placed in an arena with the choice to feed near 1) a more colorful male or a less colorful male and 2) a male with a larger gorget or a male with a smaller gorget. To separate signaling based on gorget color/ size from behavior, we used freeze-dried hummingbird mounts as stimuli rather than live animals. We predicted that if color and/ or size are used to honestly signal aggressive ability by competing males, the birds would choose to feed near the mounts displaying smaller or drabber gorgets. This would maximize the likelihood of winning and being able to feed while minimizing the energetic cost of the fight. Results will be discussed.