A test of sensory bias for long tails in the house finch

Abstract

The sensory bias model of sexual selection proposes that female preferences for certain male traits result from biases in the female sensory system that existed prior to the evolution of the preferred trait. Phylogenetic tests of the sensory bias hypothesis have provided evidence for pre-existing bias in several species, but the hypothesis has not been tested relative to elongated tail feathers, a widespread sexually selected trait in birds. Elongated tails occur sporadically across avian taxa, including cardueline finches (family Fringillidae), suggesting that long tails evolved independently in many lineages. To determine whether a female preference for longer tails predated the evolution of long tails in cardueline finches, we tested female preferences for artificially lengthened tail feathers in male house finches,Carpodacus mexicanus. The house finch is a cardueline finch species with a tail that does not appear to be elongated or sexually selected. In mate choice experiments, females did not demonstrate a preference for lengthened tails over controls. This negative result fails to support the hypothesis that elongation of tail feathers resulted from exploitation of a widespread sensory bias.