Merlin

American Oystercatcher Life History

Habitat

Habitat Shorelines

American Oystercatchers are found only in intertidal areas and adjacent beaches, especially barrier islands with few or no predators. Within this environment, they prefer sandy, shelly beaches for nesting but also nest on sandy spots in saltmarshes and even on mats of dead vegetation (wrack) in the upper part of saltmarshes. Artificial beaches, such as dredge-spoil islands, also attract oystercatchers for nesting and roosting. Migrating and wintering birds use the same habitats. During foul weather, such as tropical storms and nor’easters that prevent them from foraging, oystercatchers take shelter in other open habitats in the vicinity such as agricultural fields.

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Food

Food Aquatic invertebrates

American Oystercatchers dine almost solely on saltwater bivalve mollusks, including many species of clams and several oysters and mussels, and to a lesser degree limpets, jellyfish, starfish, sea urchins, marine worms, and crustaceans such as lady crabs and speckled crabs. Oystercatchers walk slowly through oyster reefs until they see one that is slightly open; they quickly jab the bill inside the shell to snip the strong adductor muscle that closes the two halves of the shell. Some oystercatchers smash open shells with the tip of the bill before snipping the muscle. especially when hunting softer-shelled species. Adult oystercatchers tend to teach their young one technique, either to snip or to smash, during their first year. For bivalves such as razor clams that burrow into sand, oystercatchers probe into the substrate and capture the prey by touch; they also capture mole crabs and polychaete worms in this manner. Tidal conditions influence when oystercatchers forage, and generally, they forage most heavily on falling tides, when prey is still partly submerged and actively feeding, shells open.

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Nesting

Nest Placement

Nest Ground

The female selects the nest site in vegetation on barrier beaches (usually within or behind dunes), shelly islands, dredge-spoil islands, or high marsh. The nest site usually features dune vegetation such as sea oats or beach grass and is less often among short bushes. Some pairs have been found nesting on gravel rooftops or rocky artificial islands.

Nest Description

The nest is simply a scrape in the sand, without lining.​

Nesting Facts
Clutch Size:2-4 eggs
Number of Broods:1 brood
Egg Length:2.2-2.3 in (5.6-5.8 cm)
Egg Width:1.5-1.6 in (3.9-4 cm)
Incubation Period:24-28 days
Egg Description:

Buffy gray with dark brown speckling.​

Condition at Hatching:

Active and coordinated, covered in tan down; leaves the nest within one day of hatching.

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Behavior

Behavior Probing

American Oystercatchers are monogamous and sometimes maintain a pair bond for many consecutive years. Their courtship in early spring is boisterous, with courting birds pacing quickly over the sand in unison, giving a piping call that increases in tempo, and pivoting in arcing patterns around the beach, sometimes taking to flight in pairs. A courting pair often attracts neighboring pairs to begin this display, and sometimes as many as three pairs come together in what scientists call the Piping Ceremony. Copulation often follows this display. The size of a pair’s territory probably depends on local conditions and ranges in size from about 1.7 to 5.3 acres. They sometimes establish territories within a colony of terns, Black Skimmers, or Brown Pelicans. Pairs stay very near one another for the breeding season. Male and female take turns incubating the eggs, and both defend eggs and young, driving away intruders (including other oystercatchers) with calls, chases, and aggressive flight. Young birds can dive and swim underwater to escape predators. After the nesting season the adults and young disperse, often to different locations, for the winter, and younger birds often spend one or more years away from their natal area before returning.

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Conservation

Conservation Restricted Range

American Oystercatcher populations can be highly variable from year to year in response to food supplies, and their highly restricted habitat means the birds are never particularly numerous. Partners in Flight estimates the global breeding population at 74,000. During the early 2000s, the United States breeding population was estimated at about 11,000. Partners in Flight rates the species a 14 out of 20 on the Continental Concern Score and places it on the Yellow Watch List in light of its restricted range and narrow habitat preference. American Oystercatcher is also a species of special concern in several coastal states. Oystercatchers are sensitive to human disturbance and to loss, degradation, or development of their beach habitat. Their young are vulnerable to attack by many predators, including gulls. Storms and high tides can swamp eggs or nestlings. Projections of sea-level rise suggest further steep declines during the current century without management interventions. One benefit of human activity has been the appearance of sand islands made from dredging spoils. These are usually isolated from mammalian predators and often fairly high above the water, creating safe nesting habitat.

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Credits

Lutmerding, J. A. and A. S. Love. Longevity records of North American birds. Version 2015.2. Patuxent Wildlife Research Center, Bird Banding Laboratory 2015.

Schulte, S., S. Brown, D. Reynolds and American Oystercatcher Working Group. (2010). American Oystercatcher conservation action plan for the United States Atlantic and Gulf coasts. Version 2.1.

Sibley, D. A. (2014). The Sibley guide to birds, second edition. Alfred A. Knopf, New York, USA.

Working Group, American Oystercatcher, Erica Nol and Robert C. Humphrey. (2012). American Oystercatcher (Haematopus palliatus), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

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