AUTHORS: Theodore J. Zenzal Jr., U.S. Geological Survey; Jaclyn A. Smolinsky, Cherokee Nation System Solutions; Lori A. Randall, U.S. Geological Survey; Amanda Y. Crandall, Cherokee Nation System Solutions; R. Randy Wilson, U.S. Fish and Wildlife Service; Jeffrey J. Buler, University of Delaware
ABSTRACT: Texas and Louisiana comprise a large and diverse landscape that supports billions of landbirds each migration season as they stopover to rest and refuel. The stopover habitats used by migrants are often in areas experiencing human population growth and are impacted by natural disturbances and climate change. Over the next several decades, climate change impacts (e.g., sea-level rise, extreme weather events, changes in temperature and precipitation) are expected to intensify, which may lead to habitat loss and, subsequently, loss of birds. Consequently, natural resource managers need information on how climate change indicators, such as sea-level rise and land cover change, influence stopover distributions in order to identify areas of conservation priority. We investigated predicted landbird response to climate change using historical weather surveillance radar (WSR) data and historical as well as predicted environmental variables. Our predictor variables included distance from the Gulf of Mexico and future estimates of temperature, precipitation, and several land cover variables. We used forecasted predictor variables for three future years (2030, 2060, and 2080) under two representative concentration pathways (RCP; 4.5 and 8.5). Using training data sampled from 15 WSRs across Texas and Louisiana from 13 years, we predicted estimated bird density using boosted regression tree models during spring and autumn migration for our response variable. For autumn, regardless of RCP and year, the highest estimated density of migrants was in the western Texas panhandle and the lowest density was within the Lower Rio Grande Valley. During spring migration, regardless of RCP and year, the highest densities of migrants are predicted to be in the Trans-Pecos Mountains and within the Lower Rio Grande Valley, whereas the lowest densities appear to be in the Texas panhandle as well as extreme eastern Louisiana and western extents of Texas.
