Atlantic ghost crab (Ocypode quadrata) burrow counts at shorebird nests and randomly available sites on Metompkin Island, Virginia, 2022

Atlantic ghost crabs (Ocypode quadrata) are predators of beach-nesting shorebirds, their nests, and their chicks on the United States' Atlantic and Gulf coasts. Ghost crabs may also disturb birds, altering their foraging, habitat use, or nest and brood attendance patterns. Shorebird conservation strategies often involve predator and disturbance management to improve reproductive success, but efforts rarely target ghost crabs. Despite the threat to shorebird reproductive success, ghost crabs are a poorly understood part of the beach ecosystem and additional knowledge about ghost crab habitat selection is needed to inform shorebird conservation. We monitored ghost crab activity, defined as burrow abundance, throughout the shorebird breeding season on Metompkin Island, Virginia, an important breeding site for piping plovers (Charadrius melodus) and American oystercatchers (Haematopus palliatus). We counted burrows at shorebird nests and random points throughout the shorebird breeding season and tested whether ghost crab activity was greater at shorebird nest sites than random sites. We observed burrows at all nest sites in our study area (n = 63 nests), but found fewer burrows at nest sites than random sites. Ghost crabs may avoid shorebird nest sites due to aggressive defensive behaviors from incubating adults or differences in microhabitat characteristics selected by shorebirds versus ghost crabs. We also tested the effects of date, air temperature, habitat type, and shell cover on the abundance of ghost crab burrows. We found that while burrows were present across the barrier island landscape, there were more burrows in sandy habitats with sparse to little shell cover and in and behind the dunes relative to the beach and beach-front berm. Ghost crab activity increased later in the shorebird breeding season and as air temperature increased. Understanding when and where ghost crabs are most likely to be active in the landscape can aid decision-making to benefit imperiled shorebird populations.