Signature Versus Perceptual Adaptations for Individual Vocal Recognition in Swallows

Abstract

Abstract Field experiments have shown that parents in the colonially-nesting cliff swallow (Hirundo pyrrhonota) discriminate between their offspring and unrelated young whereas parents in the closely-related but noncolonial barn swallow (H. rustica) do not, and that discrimination is based on the chick begging call. In a laboratory experiment, we trained three cliff swallows, two barn swallows and a European starling (Sturnus vulgaris) to discriminate among chick begging calls of the two swallow species. All birds discriminated more easily among the calls of different cliff swallows than among the calls of different barn swallows, suggesting that cliff swallow calls are more individually distinctive, and may be adapted for a signature function. Moreover, cliff swallows discriminated among both cliff swallow and barn swallow calls faster than did the other birds, which is consistent with a perceptual adaptation for conspecific calls that incidentally facilitates the discrimination of similarly-structured heterospecific calls.