MALE WING-PATCH ASYMMETRY AND AGGRESSIVE RESPONSE TO INTRUDERS IN THE COMMON CHAFFINCH (FRINGILLA COELEBS)

Abstract

Recent studies reveal that asymmetries of bilateral characteristics may reflect poor condition, serving as an honest indicator of mate quality. We asked whether bilateral asymmetry might also influence behavior during aggressive intrasexual contests. In the Common Chaffinch (Fringilla coelebs), bilateral, white wing patches (epaulettes) are used during aggressive interactions. We recorded responses of males to model intruders placed on territories of focal males, to determine whether their response to asymmetry varied with wing-patch size. When epaulettes were large, models with asymmetric patches elicited more rapid, directed aggression from the territory owners than did models with symmetric patches. We observed no such difference when model intruders had small epaulettes. If asymmetry of epaulettes in chaffinch males indicates poor condition, our results suggest higher costs of aggressive signaling for individuals in poor than good condition.