CONSPICUOUS COLORATION IN MALE BIRDS IS FAVORED BY PREDATION IN SOME SPECIES AND DISFAVOURED IN OTHERS

Conspicuous plumage in male birds may evolve through competition between males and choice of bright males by females. Male brightness might be constrained by increased risk of predation or other mortality agents. Alternatively, bright male birds may signal to predators that they are unprofitable as prey. These hypotheses, which have been difficult to test, were examined in a field experiment where stuffed chaffinches Fringilla coelebs and pied flycatchers Ficedula hypoleuca were exposed to sparrowhawks Accipiter nisus on spring migration in Denmark. The hawks attacked the colourful male chaffinches more often than the cryptic female chaffinches. In the flycatcher, however, hawks attacked the cryptic females more often than the conspicuous males. Risk of predation is therefore likely to influence the evolution of male coloration. It may, however, select against conspicuous plumage in some species, but favour it in others.