Tactics and Counter-Tactics of Sexually Selected Infanticide in Tree Swallows

Abstract

Infanticide, the killing of dependent, conspecific young, has only recently been recognized as an adaptive behaviour which can be moulded by natural selection through some advantage which accrues to the infanticidal individual (Trivers 1972, Hrdy 1979). Sexually selected infanticide, in which reproductively mature individuals kill offspring of another individual in order to gain a breeding opportunity, is relatively common in mammals, but apparently rare in birds (Rohwer 1986). Mock (1984) suggests the paucity of sexually selected infanticide in birds is due to the prevalence of monogamy in this taxon. However, even monogamous species can face severe competition for breeding opportunities and hence strong sexual selection (Crook and Shields 1985, Robertson and Stutchbury 1988). Recent studies (e.g. Goldstein et al. 1986, Møller 1988a, Emlen et al. 1989) reveal that sexually selected infanticide may be more common in birds than previously realized, and infanticide and its threat may be an important factor in the evolution of both male and female reproductive strategies (Freed 1987, Møller 1988a).