TEMPORAL PATTERNS IN FALL MIGRANT COMMUNITIES IN YUCATAN, MEXICO

We quantified temporal turnover in the composition of fall migrant landbird communities along the northern coast of the Yucatan Peninsula using Detrended Correspondence Analysis. The presence of winter residents of many migrant species at the site prevented turnover from being complete. However, early and late season transient communities shared few, if any, species in common. Point-count surveys showed greater compositional change than net surveys that included winter residents. The rate of species turnover was generally slow until the middle of the season, when it reached a maximum, and decreased again toward the end of the season as species composition began to converge on that characteristic of the winter community. Within-season patterns of species turnover were similar between net- and point-count surveys and were consistent across years. Species that winter farther south arrived at the site significantly earlier than those wintering at more northern latitudes; however, there was no association with breeding latitude. Additionally, insectivores arrived significantly earlier than omnivores and granivores. The amount of turnover among foliage-gleaning insectivores was less than that for all species in the community, which is inconsistent with the hypothesis that competition during migration has played a role in shaping temporal patterns in species co-occurrence and turnover. For species that co-occur in time during migration, spatial segregation at various scales, as well as differences in foraging behavior and diet, may act to reduce competition at stopover sites