American oystercatcher (Haematopus palliatus)
|Also known as:||American pied oystercatcher|
|Size||Head-body length: 40 – 44 cm (2)|
Wingspan: c. 89 cm (3)
Male weight: c. 567 g (2)
Female weight: c. 638 g (2)
Classified as Least Concern (LC) on the IUCN Red List (1).
The largest shorebird in the Americas, the American oystercatcher is boldly patterned black and white (4). This conspicuous bird has a black head, brown back and white underparts, all of which sit in stark contrast to the large, red bill, which reaches up to ten centimetres in length (3) (5). The stout, relatively short legs are a dull pink, while a bold white stripe lies on the wing, and red rings surround the bright yellow eyes (3) (6). The male and female American oystercatcher are alike, although the female is usually larger, with a longer bill, but the juvenile’s head and back are speckled brown to camouflage it against the pebbly beaches (4) (7). Restricted to the shoreline year-round, the American oystercatcher is one of the few bird species that specialises in feeding on bivalves (2). Exploiting its long, powerful beak, which is flattened sideways, this bird rapidly stabs at the muscle holding the two shells of its prey together, exposing the soft tissue inside (4).
The American oystercatcher has a large, but discontinuous range. It is found along the Atlantic and Pacific coasts of North America and Central America: from New England state in the east, south to the Gulf of Mexico, the Caribbean and Central America and from Mexico in the west, south through Costa Rica and Panama to southern Chile. It is also found along the Caribbean-Atlantic coast of South America, south to south-central Argentina (4) (7). Although many populations remain in the same place year-round, some populations begin southward migrations before the onset of winter, with large concentrations of birds gathering in northern Virginia and South Carolina (8).
The American oystercatcher occupies a variety of coastal habitats, including rocky and sandy beaches, mudflats, salt ponds, salt marsh islands, estuaries and river mouths (4) (7) (8) (9). It typically feeds on intertidal mudflats and sandbars, especially where oysters are abundant, and nests in areas with little vegetation (8) (9).
Probing at the soft substrate along mudflats and sandbars, the American oystercatcher feeds mainly on oysters, mussels, clams and limpets, as well as snails and crabs (2). Once its shelled prey is found, this large-billed bird goes about opening it up using two main methods. If its prey is taken by surprise and its shell is already open, the American oystercatcher quickly drives its bill between the shell halves, severing the adductor muscle (the muscle that holds the shell halves together) with a scissor-like movement and the flesh is chiselled out. If the shell is closed, repeated blows of the beak are used to prise the shell apart and the flesh is removed (8) (6). There is great variation between individual birds as to what prey is principally eaten and what techniques are used. Young oystercatchers rely heavily on the parents to learn these techniques, but for their first year of life they feed largely on scraps left by adults as the bill and skull is not sufficiently strong to open shells until their second year (6).
Outside of the breeding season, the American oystercatcher is highly gregarious, gathering into large flocks when foraging, roosting and migrating (4). However, during the breeding season, which takes place between February and July, monogamous pairs collect at specific breeding sites, with the female arriving up to three weeks before the male (3) (8). Once paired up, a simple nest, which is no more than a scrape in the ground, is constructed in an elevated position just above the high water mark (2) (3). During this time, the breeding pair is highly territorial and will fiercely defend an area around the nest, which may vary from just a few metres away, to a kilometre stretch of the beach (4) (7). To mark their territory, birds engage in ‘piping displays’ whereby the adult bird stands with its neck arched and bill pointed downwards, all the while emitting a series of piping notes (6). A clutch of 1 to 4 eggs is laid and subsequently incubated for 24 to 29 days by both the male and female (2) (3). To disguise the eggs, pieces of broken shell or pebbles are placed inside the nest, and to distract potential predators, the parents will feign injury away from the nest or even pretend to brood a clutch away from the actual eggs (3). Within 24 hours of hatching, the chicks are capable of running and leave the nest only 1 or 2 days later (3) (7). They learn to fly within five weeks, but due to the American oystercatcher’s specialised diet, the young continue to accompany the parents to learn the basic feeding techniques and it is several months before they become fully independent (2) (4). The American oystercatcher reaches sexual maturity after a year, and regularly lives to reach over 10 years of age, with some individuals perhaps living as long as 30 or even 40 years (3) (4).
Although the American oystercatcher is now a relatively common shorebird, it was once highly threatened and rare. During the nineteenth century its eggs were collected for food, while its conspicuous colouration made it vulnerable to hunting. These threats were exacerbated by a rapidly growing human population increasingly encroaching upon natural habitats in coastal areas. However, following the Migratory Bird Treaty Act in 1918, which afforded the species protection from these threats, its population started to recover and by the 1970s its range had expanded substantially (8).
Today, the most significant threat to the American oystercatcher is habitat loss, as well as disturbance and predation by introduced predators. Coastal developments, particularly on the United States’ Atlantic coast, are reducing the amount of nesting and foraging habitat available to this species and negatively affecting remaining natural habitats through pollution and sedimentation (4) (9). As a ground-nesting bird, its eggs are vulnerable to predation by feral cats and dogs and other predators, as well as disturbance, which can cause nesting birds to abandon eggs or chicks (4) (9) (10). The American oystercatcher is also threatened by the over-harvesting of oysters, its main food source, and catastrophic events such as oil spills, algal blooms and hurricanes (9). In addition, as this shorebird occupies low-lying coastal areas for nesting, foraging and roosting and largely feeds on shellfish at low-tide, it is particularly vulnerable to rising sea-levels caused by global climate change (4).
As the American oystercatcher is listed as a Species of Concern by the U.S. Fish and Wildlife Service, it is recognised that conservation efforts are required to tackle the threats to this species (4) (11). Thankfully, there have already been many studies into its biology, behaviour and conservation priorities, much of which have been coordinated by the American Oystercatcher Working Group (9) (12). With this shorebird occupying just a narrow stretch of coastline vulnerable to development, disturbance and rising sea-levels, conservation efforts must focus on protecting its nesting and feeding habitat, while measures should also be taken to limit disturbance and control predators (4) (8) (9). This may involve establishing further protected areas and educational awareness programmes, as well as affording existing reserves greater protection (4).
For additional information on the American oystercatcher, see:
The American Oystercatcher Working Group:
To find out more about bird conservation in the Americas, see:
The American Bird Conservancy:
The Neotropical Bird Club:
The Nature Conservancy:
For more information on this and other bird species please see:
- BirdLife International:
This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
- Algae: simple plants that lack roots, stems and leaves but contain the green pigment chlorophyll. Most occur in marine and freshwater habitats.
- Bivalve: in this group of aquatic molluscs the soft parts are encased in a shell consisting of two parts known as valves.
- Feral: previously domesticated animals that have returned to a wild state.
- Incubate: to keep eggs warm so that development is possible.
- Intertidal: pertaining to the intertidal zone, the region between the high tide mark and low tide mark.
- Monogamous: having only one mate during a breeding season, or throughout the breeding life of a pair.
- Territorial: describes an animal, a pair of animals or a colony that occupies and defends an area.
- Territory: an area occupied and defended by an animal, a pair of animals or a colony.
IUCN Red List (June, 2010)
- del Hoyo, J., Elliott, A. and Sargatal, J. (2001) Handbook of the Birds of the World. Volume 3: Hoatzin to Auks. Lynx Edicions, Barcelona.
Texas Parks and Wildlife Department (July, 2010)
- Schulte, S., Brown, S. and Reynolds, D. (2007) A Conservation Action Plan for the American Oystercatcher (Haematopus palliates) for the Atlantic and Gulf Coasts of the United States. Version 2.0. U.S. Fisheries and Wildlife Service.
The Cornell Lab of Ornithology (July, 2010)
- Perrins, C. (2009) The Encyclopedia of Birds. Oxford University Press, Oxford.
NatureServe Explorer (July, 2010)
- Nol, E. and Humphrey, R.C. (1994) American oystercatcher (Haematopus palliates). Cornell Lab of Ornithology. The Birds of North American Online.
South Caroline Department of Natural Resources (July, 2010)
- Virzi, T. (2010) The effect of human disturbance on the local distribution of American oystercatchers breeding on barrier island beaches. Wader Study Group Bulletin, 117: 19-26.
The Nature Conservancy (July, 2010)
The American Oystercatcher Working Group (July, 2010)