A Sexually Selected Paradox in the Pied Flycatcher: Attractive Males Are Cuckolded

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Evidence exists from several bird species that females prefer colorful mates (e.g. Hill 1990, Swtre et al. 1994, Sundberg 1995). Because female preferences may be manifested in social mate choice and in extrapair mate choice, one might expect colorful males to have an increased success in obtaining social mates and in achieving intrapair and extrapair fertilizations. There is empirical support for some species that colorful males do better in social and extrapair mate choice (e.g. Sundberg and Dixon 1996) and are cuckolded less frequently (e.g. Burley et al. 1996). In other species, colorful males are favored in social mate choice but are cuckolded to the same extent as are less colorful males (e.g. Hill et al. 1994). Differences among species in this respect may be related to the actual types and strength of costs and benefits relevant to females in the two contexts. In this paper, we examine the relationship between male plumage color and cuckoldry in the Pied Flycatcher (Ficedula hypoleuca). The extensive variation in plumage color of male Pied Flycatchers has generated much research and debate (see Lundberg and Alatalo 1992). Recent studies of our population in Oslo, Norway, have yielded evidence that females have a social mating preference for males with black as opposed to brown plumage (Setre et al. 1994). Black males are better food providers for nestlings than are brown males (STtre et al. 1995). Females, therefore, seem to obtain direct reproductive benefits by choosing black males as social mates. Thus, the evolution of black plumage in males is consistent with the good-parent process of sexual selection (Hoelzer 1989). Variation in male plumage color may be maintained by social and reproductive benefits to inferior males of acquiring a brown plumage (Slagsvold and STetre 1991, Sxetre and Slagsvold 1996).