Scripts from: Remotely sensed microhabitat characteristics associated with Haematopus palliatus (American Oystercatcher) nest-site selection can inform beach habitat restoration along the U.S. Atlantic Coast

Shorebird populations are in steep decline and have lost almost 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, leading to habitat loss
or degradation. Haematopus palliatus (American Oystercatchers) 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 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 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.