Using eBird to assess the impact of urban land development on Least Tern (Sternula antillarum) breeding occupancy in the Southeastern United States

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Juliemar Cuevas-Hernandez, Ryan Buron and Christina Romagosa, Wildlife Ecology and Conservation, University of Florida, Gainesville, FL, Juliemar Cuevas-Hernandez, DDCSP Collaborative, Juliemar Cuevas-Hernandez, ESA SEEDS Program, Raymond R. Carthy, Florida Cooperative Fish and Wildlife Research Unit, U.S. Geological Survey, Gainesville, FL

Background/Question/Methods
The Florida coastal population continues to grow due to its tourist attractions, recreational activities, accessibility to ports, and other sources of economic gain, resulting in increased pressure on coastal ecosystems. Human presence can alter coastal species’ habitats and behavior and introduce new threats to their survivorship. Species responses to these disturbances vary and are best evaluated independently to produce effective species-specific management practices. Previous studies have shown that Least Terns (Sternula antillarum) have dramatically shifted their nesting sites from beaches to rooftops of nearby buildings as a response to increased disturbances to natural nesting areas. The goal of this study was to explore the effects of urbanization on nesting Least Terns in Florida. This study used citizen science data from the eBird database to obtain Least Tern observations on the coast of Florida. A single-season occupancy model was used to model Least Tern occupancy during June and July for 2019. Habitat covariates for the study area such as urban land area, elevation, and water and detection covariates such as survey start time, number of surveyors, and duration of the survey were included in the model.
Results/Conclusions
Preliminary results show that Least Terns are negatively correlated with urban areas during the breeding season. Previous studies have shown that Least terns use rooftops to nest, but they are partial to areas with fewer human disturbances. Additionally, Least Terns prefer nesting in areas of higher elevations with proximity to water. Understanding how human presence and activities are affecting Least Terns will help produce effective management procedures to increase populations of this State Threatened bird. Utilizing citizen science data to answer ecological questions requires careful attention to potential spatial and temporal biases but proves to be an advantageous tool for large scale studies that otherwise might be too complex to conduct.