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Khatchikian et al. (2002) studied kleptoparasitism (food stealing) by Brown-hooded Gulls (Larus maculipennis) and Gray-hooded Gulls (Larus cirrocephalus) stealing from American Oystercatchers in a coastal lagoon in Argentina. Most kleptoparasitic attacks (96%) occurred within the first three seconds of ingestion of clams by an oystercatcher, after they had opened the valves. Gulls lacked the skills required to open clams; in two cases it was observed that gulls were unable to open stolen clams that had not been opened by oystercatchers. Gulls were never observed swallowing whole clams. The overall occurrence rate was 1.2 ± 1.3 attempts per 5 minutes; 42% of attempts were successful. All kleptoparasitic attempts were made on oystercatchers feeding on Stout Razor Clams (Tagellus plebeius). Gulls stole food from oystercatchers using two different kleptoparasitic tactics; running (used in 40% of cases) and flying (used in 60% of cases). In the first, gulls approached their hosts by running from a nearby position, while in the latter, the gulls flew toward the oystercatchers.
In a study in Argentina, Daleo et al. (2005) found that carcasses of the intertidal grapsid crab Cyrtograpsus angulatus that had been abandoned by American Oystercatchers stabbing female crabs to obtain their eggs (and, occasionally, male crabs to consume their viscera) provided a significant source of food for the intertidal scavenging snail Buccinanops globulosum.
American Oystercatchers are known to feed on a variety of intertidal benthic prey such as oysters, limpets, mussels, polychaetes, crabs, jellyfishes, sea urchins, and ascidian tunicates in the northern and southern hemispheres (Kaufman 1996; Pacheco and Castilla 2001 and references therein).
The American Oystercatcher (Haematopus palliatus) is a strictly coastal species associated with rocky and sandy seacoasts, tidal mudflats, and salt marshes. It breeds locally along the Atlantic coast from Massachusetts south to Florida and along the Gulf coast south to the Yucatan Peninsula; in the Bahamas, Greater Antilles, and Lesser Antilles; along the Pacific coast from central Baja California south to central Chile; and along the Caribbean-Atlantic coast south to south-central Argentina. The primary wintering range extends from Maryland south to southeastern Mexico on the Atlantic-Gulf coast; along the North American Pacific coast from central Baja California south to Honduras, as well as in Costa Rica; and generally in the breeding range in the West Indies and along both coasts of South America. (Kaufman 1996; AOU 1998).
American Oystercatcher numbers declined seriously in the 19th century, but recovered substantially during the 20th century. Despite disturbance in beach habitats, in many areas breeding oystercatchers are doing well, often nesting on dredge spoil islands. Davis et al. (2001) estimated the number of American Oystercatchers breeding along the entire Atlantic coast and the Gulf coast of Florida at 1,624 pairs. North of Virginia, they reported stable or slowly increasing numbers, with the range expanding as far north as Cape Sable Island in Nova Scotia. However, there is good reason for concern about overall population trajectories. From Virginia south, Davis et al. reported a decline in breeding numbers, with the number of oystercatchers breeding on barrier islands in Virginia decreasing by more than 50% in the last 2 decades of the 20th century. Given their relatively small numbers and inherently low productivity, the authors suggest that American Oystercatchers are at risk in rapidly changing coastal ecosystems. (Davis et al. 2001)
Davis et al. (2001) estimated the number of American Oystercatchers breeding along the entire Atlantic coast and the Gulf coast of Florida at 1,624 pairs. North of Virginia, they reported stable or slowly increasing numbers, with the range expanding as far north as Cape Sable Island in Nova Scotia. From Virginia south, they reported a recent decline in breeding numbers, with the number of oystercatchers breeding on barrier islands in Virginia decreasing by more than 50% in the last 2 decades of the 20th century. Given their relatively small numbers and inherently low productivity, the authors suggest that American Oystercatchers are at risk in rapidly changing coastal ecosystems. (Davis et al. 2001)
Brown et al. (2005) undertook an aerial survey to assess population size and winter distribution of the eastern subspecies of American Oystercatcher, whose winter range extends from New Jersey to Texas. Using a combination of ground and aerial counts, they estimated the population of eastern American Oystercatchers to be around 11,000.
According to Wilke et al. (2007), Chesapeake Bay, coastal bays, and barrier island shorelines of Maryland and Virginia harbor around 700 breeding pairs of American Oystercatchers. More than 80% of these are found on the east coast of the Delmarva Peninsula while fewer than 20% occur along the shorelines of the Chesapeake Bay. According to Wilke et al., the number of breeding pairs in Maryland appears to have been stable or to have increased slightly during the past 20 years.The authors report that the overall trend of the breeding population in Virginia is less clear, but that recent evidence suggests that numbers on the barrier islands are increasing after more than two decades of a declining trend. The coastal bays and barrier islands typically support between 1,500 and 2,000 wintering birds, with most occurring on the east coast of the Virginia portion of the Delmarva Peninsula. (Wilke et al 2005).
In South Carolina, Sanders et al. (2008) counted around 1,100 American Oystercatchers each year during a 3 year survey, roughly a third of them nonbreeders.
American Oystercatcher numbers declined seriously in the 19th century, but recovered substantially during the 20th century. Despite disturbance in beach habitats, in many areas breeding oystercatchers are doing well, often nesting on dredge spoil islands. (Kaufman 1996)
The American Oystercatcher breeds locally along the Atlantic coast from Massachusetts south to Florida and along the Gulf coast south to the Yucatan Peninsula; in the Bahamas, Greater Antilles, and Lesser Antilles; along the Pacific coast from central Baja California south to central Chile; and along the Caribbean-Atlantic coast south to south-central Argentina. The primary wintering range extends from Maryland south to southeastern Mexico on the Atlantic-Gulf coast; along the North American Pacific coast from central Baja California south to Honduras, as well as in Costa Rica; and generally in the breeding range in the West Indies and along both coasts of South America. (AOU 1998)
In the 1800s American Oystercatchers bred along the entire Atlantic coast, perhaps as far north as Labrador and certainly as far north as Maine. By the early 1900s, oystercatchers had disappeared from the northern part of their range and Virginia was the most northern nesting location known on the Atlantic coast. Even south of Virginia, where they once were considered abundant, oystercatcher nesting in the early 1900s was rare. This decline was generally attributed to gunners who were hunting spring long distance migrating shorebirds on coastal beaches. Oystercatchers were an easy target and their nests were destroyed. After the passage of the Migratory Treaty Act in 1918, breeding abundance and distribution of oystercatchers on the Atlantic coast increased and they now breed as far north as Nova Scotia, Canada (Sanders et al 2008 and references therein).
The American Oystercatcher is found on rocky and sandy seacoasts and islands and on tidal mudflats (AOU 1998).
Although American Oystercatchers are typically monogamous, with strong pair bonds that often persist for many years, in a dense breeding colony in New York Lauro et al. (1992) found a relatively high rate of communal nesting (one male with two females). This phenomenon appeared to be a direct consequence of the high nesting densities in this colony, resulting in a shortage of high quality territories.
The typical clutch size is 1 to 4 eggs (more for nests with two females). Incubation, which is carried out by both sexes, is 24 to 28 days. Downy young leave the nest shortly after hatching, but both parents continue to help feed young for at least two months. First flight is at about five weeks. (Kaufman 1996)
A study of breeding American Oystercatchers in coastal North Carolina found that all-terrain vehicle traffic was associated with increased rates of trips to and from the nest and reduced time incubating (McGowan and Simons 2006).
According to Wilke et al. (2007), throughout the Chesapeake region oystercatchers are facing threats common to all coastal waterbird and shorebird species, such as predation and overwash events. The threat of habitat loss to development, however, is not as alarming as in other areas of the species’ breeding range due to a significant amount of habitat being either currently protected or unfit for development and recreation purposes. Habitat loss attributed to sea level rise, barrier island dynamics, and the indirect effects of development, such as pollution and contaminants, may play more important roles in the stability of breeding and wintering habitat for the American Oystercatcher in Maryland and Virginia. (Wilke et al. 2007)
The American oystercatcher (Haematopus palliatus), occasionally called the American pied oystercatcher, or PiruPiru, is a member of family Haematopodidae. Originally called the "sea pie", it was renamed in 1731 when naturalist Mark Catesby observed the bird eating oysters.[2] The current population of American oystercatchers is estimated to be 43,000.[2] There are estimated to be 1,500 breeding pairs along the Atlantic and Gulf Coasts of the US.[3] The bird is marked by its black and white body and a long, thick orange beak.
The American oystercatcher has distinctive black and white plumage and a long, bright orange beak. The head and breast are black and the back, wings and tail greyish-black. The underparts are white, as are feathers on the inner part of the wing which become visible during flight. The irises are yellow and the eyes have orange orbital rings. The legs are pink. Adults are between 42–52 cm (17–20 in) in length.[4]
The American oystercatcher is found on the Atlantic coast of North America from New England to northern Florida, where it is also found on the Gulf coast, the Caribbean, and south to Brazil, Uruguay and Argentina. It is found also in the Pacific coast of California, Mexico, Central America, Peru, and Chile.[5] In the 19th century they became locally extinct in the northeast of the United States due to market hunting and egg collecting. After receiving protection under the Migratory Bird Treaty Act, their range extended northward to re-occupy historical habitat in New England.
During the breeding season, these birds are found along the Atlantic and Gulf Coasts and from Massachusetts south to Argentina and Chile.[6] In winter, they are found in flocks along the coast from central New Jersey to the Gulf of Mexico.[7]
During the breeding season, the American oystercatcher can be found in coastal habitats including sand or shell beaches, dunes, salt marshes, marsh islands, mudflats, and dredge spoil islands made of sand or gravel.[8] During migration and winter, they are found feeding in mud or salt flats that are exposed by the tide. They are also found on shellfish beaches at this time.[8]
Oystercatchers are closely tied to coastal habitats. They nest on beaches on coastal islands and feed on marine invertebrates. The large, heavy beak is used to pry open bivalve mollusks. Oystercatchers raise a clutch of two or three eggs.
The American oystercatcher feeds almost exclusively on shellfish and other marine invertebrates.[8] Oysters are a staple of their diet, as their name suggests, but they also eat mussels, clams, limpets, sea urchins, starfish, crabs, and worms.[8] In general, they use their bills to catch shellfish. As they walk across a shellfish bed, they look for a mollusk with a partially opened shell. When they find one, they jab their bill into the shell and sever the muscle that causes the shell to clamp shut.[8] This can be dangerous, however, as they are sometimes drowned when they don't completely sever this muscle and the shell clamps down on their bill. A strong, tightly rooted mollusk can hold the bird in place until the tide comes in.[8] They also feed by carrying loose shellfish out of the water and hammering at the shell or by probing the sand for soft-shell or razor clams.[8]
American oystercatchers first breed at an age of 3–4 years.[6]
When courting, the birds will walk together and make a single piping note. This progresses to leaning towards each other, extending and lowering the neck, and running alongside each other while calling.[8] The pair may then burst into flight and fly in a tight formation around their territory.[8]
American oystercatchers breed between April and July.[6] Their nests are shallow depressions scraped into the sand by an adult.[9] Breeding adults will make 5 or more of these scrapes, then choose one to line with shells and/or pebbles.[8] These depressions are about 8 inches (20 cm) across and 2.5 inches (6.4 cm) deep.[8] A female oystercatcher lays 2–4 eggs per nest. Each egg is 2.1–2.3 cm (0.83–0.91 in) long and 1.5–1.6 cm (0.59–0.63 in) wide. The eggs are gray and speckled with dark brown.[8]
Although the eggs are well camouflaged, they are vulnerable to predation by raccoons, coyotes, skunks, gulls, crows, rats, and foxes.[2]
Both parents will alternate incubating the eggs for 25 to 27 days.[9]
One parent tending eggs Cape May Point State Park, USA
20 minutes later, its mate assumes incubation duties.
When born, the chicks are covered in tan down[8] and can run within 2 hours of hatching.[2] They are considered semi-precocial young as they can leave the nest soon after hatching but still rely on their parents for food.[3] Chicks will fledge at about 35 days old[9] After fledging, chicks still rely on their parents for food[3] as it takes up to 60 days for the beak to become strong enough to pry open mollusks.[2] During this time, care of the chicks is evenly divided by the parents.[3]
Historically, the American oystercatcher was hunted to near extinction in the 19th century for plumage and eggs.[2] They have recovered significantly since the passage of the Migratory Bird Treaty Act in 1918.[2] The IUCN lists this species as being of "Least Concern". The reasons given are that the bird has a very wide range and that the total number of individuals is believed to be stable, and actually increasing in the case of the United States.[1] Nevertheless, in some states American oystercatchers are listed as a species of concern because of low and declining populations. The North American population of American oystercatchers was listed on the 2014 State of the Birds Watch List.[2] Although not listed as a federally threatened or endangered species, it is vulnerable to loss of habitat due to development on the coasts[6] and sea level rise.[2] These birds are also threatened by pollution, disease, and invasive species which can impact food availability.[2]
_in_flight.jpg)
In flight in western Florida
Nesting on Santiago Island, Galápagos Islands
Two standing near their eggs in a nest on the Atlantic coast, New Jersey, USA
Eggs
The American oystercatcher (Haematopus palliatus), occasionally called the American pied oystercatcher, or PiruPiru, is a member of family Haematopodidae. Originally called the "sea pie", it was renamed in 1731 when naturalist Mark Catesby observed the bird eating oysters. The current population of American oystercatchers is estimated to be 43,000. There are estimated to be 1,500 breeding pairs along the Atlantic and Gulf Coasts of the US. The bird is marked by its black and white body and a long, thick orange beak.
