Quiet flight, the leading edge comb, and their ecological correlates in owls (Strigiformes)

Abstract

Abstract Owls have evolved sensitive hearing facilitated by a facial disc, and flight that is quieted in part by a leading-edge comb on their wing. This comb is a series of modified barbs, or serrations, which project up from the outermost primary feathers on the leading edge of the wing. Here we explore the evolution of comb and facial disc morphology. We measured leading-edge comb morphology on museum skins of 147 owl species, and facial disc morphology from photos, as well as ecological traits, on 66 species. The first principal component of comb morphology loaded on serration length, which varied between 0 and ~6 mm long in the species we sampled. Comb size (PC1) was correlated with relative facial disc size, suggesting that owls with good hearing also tend to have quiet flight. Two non-exclusive hypotheses for why quiet flight evolved are for stealth, allowing the owl to approach prey undetected; or to reduce self-masking, enabling the owl to hear prey better midflight. We examined whether ecological variables (prey type, active period and habitat) suggest whether stealth or self-masking better explain the evolution of comb size. Phylogenetic analyses suggested support for both the stealth and the self-masking hypotheses for the evolution of quiet flight.