Impacts of Temperature on Least Terns

The Least Tern (Sternula antillarum) is a threatened species in Florida that nests along select beaches along the Gulf Coast. In recent decades, due to habitat loss and degradation, they have begun nesting on gravel rooftops as well. Heat is a known stressor to these birds during the nesting season, with hotter temperatures known to cause higher rates of egg failure and chick mortality, and even colony abandonment in certain scenarios. In this study, we aimed to determine how heat impacts the behavior of nesting Least Terns on rooftops and beaches along the Central Gulf Coast Region of Florida. We hypothesized that rooftop Least Tern colonies would demonstrate higher rates of heat stress. We used HOBO Data loggers to record surface temperatures at beach and nest colonies in Pinellas, Pasco, and Sarasota Counties. In addition, we used solar-powered infrared-triggered cameras to record behaviors of adult Least Terns incubating eggs, such as their posture, orientation, and presence. We did not find any significant differences in heat stress behaviors between rooftop and beach colonies. However, across all colonies, we found that higher temperatures were associated with higher rates of nest presence, as well as higher rates of shading behaviors. In addition, rooftop temperatures had significantly higher daily maximum temperatures than beach locations. This summer was the hottest on record for several weather stations in Florida, and with temperatures continuing to trend upwards across the globe due to climate change it becomes imperative to determine the impacts these temperatures will have on imperiled seabirds.