Meeting Abstract
Intrasexual competition is an important selective force that can favor the evolution of honest signals of fighting ability or dominance. Competition for breeding and non-breeding resources occurs in both sexes, but research in this area focuses predominantly on males. However, females in many taxa possess ornaments or armaments that could mediate the outcome of female competitive interactions. Plumage coloration is one such ornament and in males the size and/or reflectance of plumage areas is associated with the outcome of male competitive interactions. We examined the relationship between blue and white structural coloration and aggression in female tree swallows (Tachycineta bicolor). We assessed aggression by placing a caged second-year (SY) female tree swallow 2 m from the nest box of a focal female and quantified the focal female’s response. We predicted that females with brighter white and brighter and bluer plumage would respond more strongly to the intruder. Contrary to our prediction, we found no relationship between blue coloration and aggressiveness towards the intruder. Rather, females with dull white breast coloration responded more strongly to the intruder whereas females with bright white breasts spent more time perched on their nest box. These results indicate that plumage color in female tree swallows may not be a honest signal of aggressiveness. Rather, dull white females may be more motivated to defend their nest site or may perceive a SY female intruder as a greater threat than females with bright white breasts.
