Hidden leks in a migratory songbird: mating advantages for earlier and more attractive males

In some socially monogamous birds, territories sometimes occur in aggregations. The “hidden lek” hypothesis suggests that territorial aggregations might be explained by males establishing territories near successful males (“hotshot” model), or by females preferring to mate in large clusters (“female preference” model). In both scenarios, clusters would provide more opportunities for finding mates and achieving extra-pair copulations. Our study tests predictions of these two models in the blue-black grassquit (Volatinia jacarina). Males of this species migrate to their breeding grounds, establish territories within clusters and initiate courtship displays. These displays consist of vertical leaps synchronized with vocalizations, or only the latter, without leaps. The “hotshot” model predicts that: 1) earlier-arriving males would establish territories more centrally within clusters; 2) earlier or centrally positioned males would produce more elaborate displays; and 3) these same males wou...