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When animals choose habitats and territories in which to live or reproduce, their preferences can be affected by two sets of factors: habitat quality and conspecifics. There is general agreement among theoreticians and empiricists that animals should prefer to settle in habitats with high ‘‘intrinsic quality,’’for example, in areas that offer high resource densities, protection from predators and parasites, or other features that enhance growth, survivorship, or offspring production (Fretwell and Lucas 1970; Rosenzweig 1985, 1991; Ens et al. 1992; Schieck and Hannon 1993; Yosef and Grubb 1994; Sutherland 1996). There is much less agreement, however, in either the theoretical or the empirical literature with respect to the effects of conspecifics on habitat selection (review in Stamps 1994).

One large and influential body of theory holds that, because conspecifics are competitors, individual fitness should monotonically …