HIDDEN LEKS: SEXUAL SELECTION AND THE CLUSTERING OF AVIAN TERRITORIES

The discovery that socially monogamous birds copulate outside the pair-bond compels us to view mating and parental care relationships separately. The operation of sexual selection via extra-pair copulation suggests that the mating behaviors of monogamous species are more similar to those of promiscuous spe- cies than previously thought. Males in many promiscuous species aggregate in display arenas called leks, which form in response to females seeking copulation. This chapter reviews and synthesizes evidence that the mating systems of mo- nogamous birds that pursue extra-pair copulations resemble those of promiscuous species. Razorbills (Alca torda) demonstrate that males in a monogamous species form leks for extra-pair copulation. Results from studies of Purple Martins (Prog- ne subis) indicate that lek mechanisms may contribute to colony formation. These studies, combined with other evidence, suggest that the lek models can operate in many more contexts than those in which they were originally proposed. The "hidden lek" hypothesis predicts that the same mechanisms that form leks in promiscuous species can also explain certain aggregations of territories of mo- nogamous species.