Opposing mechanisms drive diversity patterns of core and occasional bird species

This talk was presented at the 2011 Ecological Society of America annual meeting on 8/12/2011. It describes research on environmental drivers of avian species richness across the United States from surveys conducted by the North American Breeding Bird Survey. We divided communities into core species, those that were observed to occur consistently through time, and transient (or 'occasional') species, those that were only observed infrequently, and showed that different environmental factors were correlated with richness in each of these two groups. We concluded that different mechanisms determine the number of core and transient species in ecological communities.