Asymmetric Antagonism between Piping Plovers (Charadrius melodus) and American Oystercatchers (Haematopus palliatus), New York, USA

Anecdotal observations of American Oystercatchers (Haematopus palliatus) destroying Piping Plover (Charadrius melodus) eggs and killing Piping Plover chicks may be limiting Piping Plover productivity. Therefore, 212 focal observations of Piping Plovers and American Oystercatchers were recorded during the 2011 and 2012 breeding seasons at Breezy Point, New York, USA. Thirty agonistic interspecific interactions were observed, almost half (n = 13) of which occurred between Piping Plovers and American Oystercatchers. Piping Plovers initiated significantly more agonistic interactions (76%, n = 13) toward American Oystercatchers than those initiated by American Oystercatchers (8%, n = 13) toward Piping Plovers. All agonistic interactions between Piping Plovers and American Oystercatchers began after one of the species entered the territory of the other. These interactions appear to have a higher potential for fitness reduction in Piping Plovers than American Oystercatchers, and occurred approximately once every 12 hr of observation. Due to the similarity between nesting habitats of Piping Plovers and American Oystercatchers, a plan that focuses on habitat enhancement for beach-nesting birds rather than individual species is recommended.