Modeling productivity for American oystercatchers (haematopus palliatus) and Wilson's plovers (charadrius wilsonia) in a highly dynamic environment
Sterling, Abby Vaughan
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Nest site selection is an important component of breeding ecology for all birds, but beach-nesting shorebirds, which use a restricted and specific habitat, face multiple, significant challenges. I examined how habitat features and nest-site selection influenced several aspects of overall productivity for American Oystercatchers (Haematopus palliatus) and Wilson’s Plovers (Charadrius wilsonia), two species of conservation concern that nest on the Georgia coast. First, I used a multi-scale modeling approach to determine habitat features that best predicted nest site selection and daily survival of nests for both species. The results pointed to a potential mismatch between habitat cues used for nest site selection and those that are predictive of daily nest survival, which could indicate that these sites are acting as an ecological trap and have significant conservation implications. Additionally, I found that nest site selection and nest success were not predicted by the same habitat features for both species, and found that models were better at predicting nest success for Wilson’s Plovers than for American Oystercatchers. With these results in mind, I used competing risks models to look at how the dual threats of predation and overwash were influenced by habitat features, and how these threats influenced nest survival of Wilson’s Plovers. I found that predation risk was high, but not well predicted by habitat features and while tidal overwash risk was variable by year, it was better predicted by habitat features, such as elevation and community type. Finally, I estimated fledging success for Wilson’s Plover chicks, and investigated how environmental variables influenced survival. The survival estimates for chicks were low compared to other published estimates, and I found that environmental factors could be influencing nest success and chick survival differently. The results from this study suggest that active conservation efforts focused on multi-species management during both the nesting and fledging stages are necessary for protecting these shorebird species to ensure their viability on the Georgia coast.