Presence of ghost crabs and piping plover nesting success

Abstract

Despite intensive management to protect the federally threatened piping plover (Charadrius melodus), breeding success in North Carolina has consistently been lower than in other Atlantic Coast states. The native ghost crab (Ocypode quadrata) preys on plover eggs and chicks, but the effect of ghost crab predation on plover productivity has not been established. We used daily records of nest survival collected at Cape Hatteras National Seashore, North Carolina, USA from 2008 to 2015 to test a hypothesized negative relationship between the presence of ghost crabs within the 3-m diameter nest exclosure and the daily nest survival of plovers. We detected ghost crabs or their burrows within the nest exclosure on 63 out of 2,347 nest visits (24 out of 94 nests, 25%). We determined 9 nests (9.6%) were depredated by ghost crabs and 2 nests were abandoned after ghost crab visits. The estimated daily survival rate (DSR) of plover nests decreased with nest age, so to compare the nesting success predicted by our model, we standardized age in the prediction as the age at mid-incubation. At mid-incubation (nest age = 19 days), the DSR of a nest found with evidence of ghost crabs was 0.92 (95% CI = 0.74–0.98), compared to DSR of nests without ghost crabs (0.99, 95% CI = 0.97–0.99). We tested other covariates (e.g., clutch size, breeding timing, daily weather conditions); however, the standardized effect size of the presence of ghost crab was more than twice that of all other covariates. Ghost crabs may have a previously under-recognized effect on plover nest survival when avian and mammalian predation is precluded by nest exclosures. Protection of piping plover nests from ghost crabs may improve piping plover nest success. © 2018 The Wildlife Society.