Substrate-Level Nest Site Selection of Sympatric Piping Plovers (Charadrius melodus) and American Oystercatchers (Haematopus palliatus) in New Jersey, USA

Abstract

Piping Plovers (Charadrius melodus) and American Oystercatchers (Haematopus palliatus) are shorebird species of conservation concern that breed sympatrically along the U.S. Atlantic coast, facing substantial anthropogenic habitat loss and disturbance. Interspecific aggression has been increasingly observed in overlapping habitat, potentially resulting in diverting time and energy that would be available for breeding activities. Because nests are camouflaged against the substrate, nest site habitat is important to fitness. Understanding habitat selection disparities could inform management of both species while ameliorating agonistic interactions. Nest sites in New Jersey were compared with paired random sites based on median proportions of substrate covered by rock, shell, wrack, plant, and other items (including peat and plastic litter). Both American Oystercatchers (n = 37 nests) and Piping Plovers (n = 42 nests) selected certain substrate features in amounts disproportionate to their availability, and interspecific differences were present. For American Oystercatchers, wrack constituted 17.7% of the substrate at nest sites versus 2.0% at paired sites. Piping Plover nest sites had greater proportions of shells, and medium fragments (2-64 mm) alone represented 18.9% of nest substrate versus 6.3% at paired sites. Results indicate that substrate management may be effective in creating ecological separation between these species.