European barn swallows use melanin pigments to color their feathers brown

The barn swallow (Hirundo rustica) has figured largely in studies of sexual selection and exaggerated traits (Møller, 1994, 2001). In addition to the elongate tail streamers that confer a series of reproductive advantages to individuals in European populations, these birds develop a brown patch of feathers on the face and throat that has also been the focus of several empirical tests of honest advertisement theory (e.g. Camplani et al., 1999, Saino et al., 1999). Researchers studying this trait have assumed that these feathers contain carotenoids, and several conclusions have been drawn about the physiological and sexual functions of carotenoids in relation to this color ornament (Camplani et al., 1999, Saino et al., 1999). However, to date there is no biochemical evidence in the primary literature supporting the idea that brown feathers in barn swallows contain carotenoids. Here, we demonstrate that barn swallows from Europe (Hirundo rustica rustica) do not deposit carotenoids into brown feathers, but instead color this plumage with melanins.