Factors limiting the distributions of trailing-edge populations in the Southern Appalachian Mountains

The ranges of many species are shifting toward higher latitudes because of climate change, affecting the viability of many trailing-edge populations. Forecasting the dynamics of these populations requires information about the factors limiting their distributions. To understand the roles of abiotic and biotic factors in limiting trailing-edge populations of bird species in the southern Appalachian Mountains, I collected three years of point count data and conducted two manipulative experiments. One manipulation used simulated territory intrusions to understand the role of interference competition between a cool-adapted species (Cardellina canadensis) and warm-adapted species (Setophaga citrina). The other used playback to assess the role of socially-mediated Allee effects in limiting the distribution of C. canadensis. My results indicate that trailing-edge populations of cool-adapted species are more strongly affected abiotic factors than by competition with warm-adapted species. In addition, I found no evidence that socially-mediated Allee effects limit the distributions of trailing-edge populations.