Linking Thresholds in Avian Body Condition and Habitat Usage to Short and Long Term Climatic Events

Abstract

I conducted a series of studies focused on the central theme of avian response to disturbance. As climate change and altered disturbance regimes continue to affect ecological communities, thoroughly understanding the manifestation of these effects at different scales is critical to future conservation planning. In my first chapter, I investigated avian habitat relationships in a mesquite-huisache shrubland ecosystem within the Coastal Prairie ecoregion. By using a point count sampling array in conjunction with vegetation transects I found that huisache and Old World bluestems, two invasive plant species in the region, had surprisingly little effect on avian occupancy and diversity at a local scale. I also documented annual variation in occupancy and density which yielded insights to avian resilience and recovery in the years following a major hurricane. In my second chapter, I turned to investigating the effects of short-term weather on individual avian body condition of three songbird species at a local scale in coastal Texas. Despite an abundance of literature discussing the long-term effects of climate change on birds, the effects of short-term weather are less studied. I found that both short-term precipitation and temperature can affect avian body condition and that some species exhibit a threshold effect. Finally, in my third chapter I use a large existing dataset to investigate the wider effects of precipitation and temperature on avian body condition at a regional scale across five southeastern US states. I again found that threshold effects to these weather variables were common across species, and surprisingly that guilds were generally ineffective predictors of species-level responses. These findings can have further implications for individual fitness and overall population dynamics. Together, these chapters highlight several key factors that can affect birds in light of continued climate change and demonstrate that avian responses to short-term weather may be difficult to predict across species.