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 extrapair 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 would achieve higher success via within and extrapair fertilizations. The “female preference” model predicts that: 4) pairing success and 5) per-capita extrapair fertilizations would increase with cluster size. We found that earlier-arriving males executed higher leaps and longer songs, but there was no relationship between these traits and male position within clusters. We also found that earlier-arriving males were more likely to obtain extrapair fertilizations. However, we found little evidence that cluster size related to overall or per-capita breeding success. Considered together, our data provide partial validation of the hotshot model of hidden leks and expand on prior findings in this species by showing that females benefit by choosing males leaping higher and settling earlier in clusters.