Sexual selection and tail streamers in the barn swallow: appropriate tests of the function of size-dimorphic long tails

Abstract

In their recent forum paper, Thomas and Rowe (1997) question our tail manipulation experiments used to test sexual selection theory (Cuervo et al., 1996; de Lope and Møller, 1993; Møller, 1988, 1989, 1992b, 1994b; Møller and de Lope, 1994; Saino and Møller, 1996; Saino et al., 1997a, b). In summary, Thomas and Rowe claim that manipulations shortening and elongating the outermost tail feathers of barn swallows Hirundo rustica (see Møller, 1988, for a description of methods) are based on faulty logic and therefore cannot test the function of long tails. Several of their statements are unclear, incorrect, or need clarification for understanding the significance of tail manipulation experiments, and we will discuss these statements here. Thomas and Rowe repeat what has already been stated by Evans and Thomas (1997). We have responded to that paper elsewhere (Møller et al., 1998), and here we concentrate on the aerodynamic issues.