The Avoidance-Image Hypothesis and Color Polymorphism in Buteo hawks

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Abstract
The avoidance-image hypothesis proposes that conspicuous, dark-phased raptors invade populations consisting exclusively of light-phased individuals because prey previously attacked by light individuals more strongly avoid light than dark individuals in subsequent attacks (Rohwer 1983). We extend this hypothesis to predict (1) that migratory species of Buteo are more likely to be color polymorphic than resident species, (2) that, among polymorphic species of Buteo, migrants should occur in more than two morphs and residents in just two, and (3) that pairing preferences should be disassortative in dimorphic species. Without information on the genetic control of color variation in highly polymorphic species, pairing preferences cannot be predicted. Comparative data support predictions (1) and (2); few data relevant to prediction (3) exist. The striking color dimorphism and random pairing of the colonial-breeding Falco eleonorae is argued not to violate predictions of the avoidance-image hypothesis.

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