Habitat selection of an endangered marsh bird varies by tidal stage and captive or wild origin

A thorough understanding of habitat selection is vital for making informed management decisions for recovery efforts of endangered species. The light-footed Ridgway's rail (Rallus obsoletus levipes) is a federally endangered species that relies on tidal marshes, but little is known about how tides influence microhabitat selection. We used solar-powered GPS transmitters to compare habitat selection in response to tidal stage between 46 captive-released and 42 wild-caught juvenile rails at three marshes in San Diego County, California. When all GPS data were pooled across all tide stages, we could not detect differences in habitat selection between captive-released and wild-caught rails. However, when we examined high and low tide separately, important differences emerged. No statistical differences were found between captive-released and wild-caught rail habitat selection at low tide. Wild-caught rails showed stronger selection of high marsh relative to mid-marsh at high tide, whereas captive-released rails avoided high marsh. This difference in behavioral patterns may leave captive-released rails more exposed to predation risk. Our study emphasizes the relevance of designing habitat selection analyses that incorporate temporal changes in habitat availability (especially in tidal ecosystems), and of understanding potential differences in habitat selection between captive-released and wild individuals.