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Citation. McKinney, F.; Cheng, K. M.; Bruggers, D. J. 1984. Sperm competition in apparently monogamous birds. Pages 523-545 in R. L. Smith, editor. Sperm Competition and the Evoloution of Animal Mating Systems. Academic Press, New York. [1421 CC]
Introduction. Students of avian mating systems generally agree that most bird species are monogamous. Usually the generalization is made either to contrast birds with mammals, in which pair-bonding is rare, or to emphasize that the spectacular avian examples of polygyny, polyandry, and promiscuity really are exceptional phenomena in birds (e.g., Lack 1968, Selander 1972, Emlen and Oring 1977). Monogamy is a "prolonged association and essentially exclusive mating relationship between one male and one female" (Wittenberger and Tilson 1980). Although this definition states that mates normally copulate only with one another, the literature contains many reports of extrapair copulations in monogamous birds (Table I). Such incidents have usually been regarded as exceptions to the species-typical pattern of behavior, and until very recently the possibility that they can result in the fertilization of eggs has not been seriously considered. The purpose of this paper is to review the evidence relating to this possibility and to evaluate the potential for sperm competition (as defined by Parker 1970) in species generally considered to be monogamous.
Keywords. monogamy, extrapair copulations, sperm competition