American oystercatchers are fairly large shorebirds. They are 40 to 44 cm long, have an average wingspan of 81 cm, and weigh between 400 and 700 g. Although males and females look similar, females tend to be larger. American oystercatchers are dark brown on the nape of their neck and wings, with black heads and necks. Bright white undersides contrast greatly with these dark upperparts. The narrow white wing patch and white "V" on their upper rump is visible when they fly. Their long, straight bill is red to orange, with dark colorings toward the end in juveniles. Their legs are long and pale pink. Their iris is bright yellow with a visible red eye ring. Their black head and neck, brown mantle, red eye ring, and yellow eyes help to tell them apart from other species. (Elphick, et al., 2001; Nol and Humphrey, 1994; Stokes and Stokes, 2013)
American oystercatchers (Haematopus palliates) are found in the United States, Cuba, Brazil, and Mexico. They are the only oystercatcher species native to the Atlantic Coast of North America. Along the Atlantic Coast, their breeding range spans between Massachusetts and Florida. American oystercatchers can be found year-round throughout parts of the Caribbean and the Gulf Coast. In South America, they are found as far south as Chile and Argentina; they are also found on both coasts of Mexico and Central America, breeding as far north as Baja, California. There is still little known about their migration routes. (Elphick, et al., 2001; George, 2008; Nol and Humphrey, 1994)
American oystercatchers are commonly found on mudflats, sandy beaches, and occasionally on rocky shores. They nest in upland dunes, marsh islands, and beaches. Nesting may occur more often in salt marshes along the northern end of their range to avoid human disturbed areas. During the winter months, American oystercatchers tend to be found in areas with food sources such as reefs, oyster beds, or clam flats. During spring and fall migration, these birds can be found in shellfish beds, sand flats, or intertidal mudflats. They rarely travel inland; they roost on nearby dunes, marsh islands, or beaches. They usually nest 1 to 2 m above sea level. Higher elevation nests are less likely to be damaged by tidal flooding, but are more vulnerable to predators such as skunks and minks. (Elphick, et al., 2001; Nol and Humphrey, 1994; Stokes and Stokes, 2013)
American oystercatchers are usually monogamous, meaning they mostly breed within a mated pair; however, birds with several partners have been recorded in this species. Pairs bond in the spring when the birds arrive at the breeding grounds. Most birds choose a new mate each year, but some pairs maintain their partner throughout their lives. American oystercatchers attract their mates by performing courtship displays. Courting birds walk parallel to one another while holding their necks outstretched, looking downwards, and making a loud piping call. Next, they bob their heads up and down and run side by side while changing the pitch and intensity of their call. (George, 2008; Nol and Humphrey, 1994)
American oystercatchers usually breed between February and July and raise one brood per summer. Both parents are involved in nest building, brooding, incubation, and nest defense. Adults make shallow scrape nests with their feet. They often make several scrapes before selecting the one to use. Older scrape nests are sometimes reused. Most nests are found on salt marshes, rocky shores, or beaches. Sometimes they are lined with plant matter and pebbles to hide them from predators. Chicks leave the nest within 24 hours of hatching. Both parents feed the chicks until they fledge; some juveniles remain with their parents for up to 6 months. American oystercatchers are ready to mate by about 3 or 4 years old. (Elphick, et al., 2001; Lauro and Burger, 1989; Nol and Humphrey, 1994)
Both sexes invest a great deal of time and energy to raise their chicks. Males and females both make scrape nests several weeks before the egg are laid. While both parents incubate the eggs and feed the nestlings, females tend to spend more time brooding and males tend to do more of the feeding. Chicks rely on their parents for food until their bills become strong enough to probe and stab, a process that takes about 60 days. During this time, adults retrieve the soft parts of marine invertebrates and either carry them back or eat and regurgitate them for their young. In areas where there are many American oystercatcher nests nearby, they may help each other raise their offspring. (George, 2008; Lauro and Burger, 1989; Nol and Humphrey, 1994; Nol, 1985)
Many birds in order Charadriiformes are long lived, including American oystercatchers. Re-sightings of banded individuals shows that these birds often live to be 10 years and older. The oldest documented American oystercatcher was 17 years old. Some may even survive up to 20 to 40 years, like their close relatives, European oystercatchers. (Nol and Humphrey, 1994)
American oystercatchers migrate each year and are active during the day. They also make loud, recognizable "wheep" or "wee-ah" calls. They are a social species and tend to roost communally in groups of up to 100 or more individuals. During the day, these birds can be seen running or walking more often than flying. Their normal flight pattern of rapid and deep wing beats becomes softer during courtship displays and when predators are nearby. Much of their day is spent preening, head scratching, sleeping, standing, and sunbathing. (George, 2008; Nol and Humphrey, 1994; Stokes and Stokes, 2013)
There is little available information on the home range size of American oystercatchers.
American oystercatchers are very vocal, especially during the breeding season. Their breeding displays include sight and sound. Their call is loud and rises and falls. It is used for greetings between individuals, warning alarms, territorial disputes, establishing dominance in feeding areas, and begging for food from parents. (Nol and Humphrey, 1994; Stokes and Stokes, 2013)
American oystercatchers eat mostly marine invertebrates, bivalves, mollusks, worms, clams, crabs and shell fish, they also eat small fish. They mostly forage near the tide in areas with many marine invertebrate species. Their long, brightly colored bills help them prey on bivalves and search for marine invertebrates. These birds use two feeding styles. The first style is called "stabbing", where a bird walks around a shellfish bed until it finds an open bivalve, which it quickly stabs. This technique can be risky, since deeply rooted bivalves can clamp down on their bill and hold it down until the bird drowns in the rising tide. The second feeding style is called "hammering", in which the bird simply plucks a single mussel from a group of mussels, takes it to a different location, and holds it in its beak in such a way that when it begins hammering, the shell breaks easily and the chain that holds the bivalves together is severed. Their major food items include soft-shell clams, blue mussels, sandworms, razor clams, oysters, and mole crabs. (George, 2008; Nol and Humphrey, 1994; Stokes and Stokes, 2013)
While skunks, raccoons, great black-backed gulls, and herring gulls all prey on American oystercatcher eggs, large raptors are the primary predators of adult birds. Some American oystercatchers are also preyed on by black-crowned night herons and American crows. However, humans, domestic cats, and domestic dogs likely pose the biggest threat to American oystercatchers. (George, 2008; Nol and Humphrey, 1994)
American oystercatchers and closely-related Eurasian oystercatchers may steal prey from other species. Common gulls also use American oystercatchers to find food. (Martinez and Bachmann, 1997; Nol and Humphrey, 1994)
There are no known adverse effects of American oystercatchers on humans.
American oystercatchers are a species of least concern in many coastal states. However, because they are rather shy birds, they do not do well with human interaction and they are losing habitat to human disturbance and development along beaches. American oystercatchers tend to avoid nesting near gulls where their nests would be vulnerable to attacks. Hunting and egg collecting in the 19th Century can also help explain the low population numbers in North America. (George, 2008; Nol and Humphrey, 1994)
Maddie Hardin (author), University of Wisconsin - Stevens Point, Christopher Yahnke (editor), University of Wisconsin-Stevens Point, Leila Siciliano Martina (editor), Animal Diversity Web Staff.
Elphick, C., J. Dunning Jr., D. Sibley. 2001. The Sibley Guide to Bird Life and Behavior. New York: Alfred A. Knopf.
George, R. 2008. "Reproductive Ecology of the American Oystercatcher (Haematopus palliatus) in Georgia" (On-line pdf). Accessed August 10, 2013 at http://athenaeum.libs.uga.edu/bitstream/handle/10724/5995/george_russell_c_200208_ms.pdf?sequence=1.
Lauro, B., J. Burger. 1989. Nest-site selection of American Oystercatcher (Haematopus palliatus) in Salt Marshes. The Auk, 106: 185-192.
Martinez, M., S. Bachmann. 1997. Kleptoparasitism of the American Oystercatcher. Marine Ornithology, 25: 68-69.
Nol, E. 1985. Sex Roles in the American Oystercatcher. Behaviour, 95: 232-260.
Nol, E., R. Humphrey. 1994. American Oystercatcher (Haematopus palliatus). The Birds of North America, No. 82: 1-23.
Stokes, D., L. Stokes. 2013. The New Stokes Field Guide to Birds Eastern Region. New York, Boston, London: Little, Brown and Company.