Remotely sensed microhabitat characteristics associated with <i>Haematopus palliatus</i> (American Oystercatcher) nest-site selection can inform beach habitat restoration along the U.S. Atlantic coast

ABSTRACT Shorebird populations are in steep decline and have lost ∼70% of their North American populations, on average, since 1970. The declines are accelerating for most species, in part because coastal environments face significant threats from anthropogenic activities. Haematopus palliatus (American Oystercatcher) have begun to recolonize areas in their northern breeding range where they were previously extirpated; however, threats persist due to habitat loss, human disturbances, and high predation risk. Coastal habitat restoration, particularly the use of dredged material to enhance and create beach habitats, has been shown to be a viable conservation strategy. To inform restoration design, this study aims to quantify the microhabitat characteristics influencing H. palliatus nest-site selection across sandy beaches along the U.S. Atlantic coast, utilizing high-resolution LiDAR (light detection and ranging) data. We analyzed 1,349 nest locations compiled from targeted surveys, comparing them to randomly generated pseudo-absence points. We calculated 17 geomorphological variables representing microhabitat from public domain, LiDAR-based digital elevation models and employed boosted regression trees to model their relationship to nest presence. Results indicated that nest elevation, distance to mean sea level and mean high water, and shoreline sinuosity were the most important predictors of nest presence, with differences observed between northern and southern regions. In the northern states from New Jersey to Connecticut, low shoreline sinuosity was most important, likely due to its role in reducing predation risk, whereas in the southern states from Virginia to Florida, nest elevation emerged as the dominant factor, suggesting a regional adaptation to the more rapid increases in sea level rise along the southern Atlantic coast. These findings highlight the importance of microhabitat characteristics in the design, restoration, and management of shorebird nesting habitats, and can contribute to best practices for conservation efforts aimed at sustaining H. palliatus populations amidst escalating coastal threats.