The Breeding Status of the American Oystercatcher on the East Coast of North America and Breeding Success in North Carolina

-We studied American Oystercatchers (Haematopus palliatus) by examining reproductive success and the factors affecting it at one location, and by examining the status and trends of breeding population numbers from Florida to Nova Scotia on the east coast of North America. We conducted our field research on Cape Lookout National Seashore, Carteret County, North Carolina from 1997 to 1999, and we documented larger scale breeding population trends by contacting state biologists and reviewing the literature and historical accounts. Presence of eggs and young were checked two to five times per week (by observing from a distance), and efforts were made to determine the reasons for loss of the nest contents. We monitored a total of 245 nests and found low productivity. At least one egg in 32 (13%) nests hatched and one or more chicks fledged from 12 broods. Overall, 14 chicks successfully fledged (nine from North Core Banks and five from South Core Banks) during the three years of the study. Of the 213 clutches that did not hatch, 163 (76%) failed because of predation, and 46 (22%) because of overwash or severe weather. Our minimum estimate for the number of oystercatchers breeding along the entire Atlantic coast and the Gulf coast of Florida is 1,624 pairs. North of Virginia, numbers appear to be stable or slowly increasing and the species has expanded as far north as Cape Sable Island in Nova Scotia. From Virginia south, breeding numbers show a decline in recent years. The number of oystercatchers breeding on barrier islands in Virginia has decreased by more than 50% in the last 20 years. Given their relatively small numbers and inherently low productivity, American Oystercatchers are at risk in rapidly changing coastal ecosystems. Received 1 June 2000, accepted 11 October 2000.