On Exhibit: Open Sea
intertidal marine invertebrates, such as bivalves, limpets, whelks and chitons
17.5 inches (44 cm)
along the Pacific coast from the Aleutian Islands to Baja California
Despite its name, this brownish-black bird with large feet seldom eats oysters. At low tide, it forages along rocky shorelines, looking for other molluscs—mostly limpets and mussels.
A breeding pair of oystercatchers select a nesting site above the high tide level and near an area with plenty of food. The pair defends the area against other oystercatchers and intertidal foragers. In winter, the oystercatchers gather in flocks that remain close to their breeding sites.
According to the U.S. Fish and Wildlife Service, the entire world population of black oystercatchers is estimated at about 11,000 individuals—more than 50 percent of that population lives in Alaska. Direct and indirect effects of human disturbances probably have reduced the oystercatcher population from much higher historical levels.
Since oystercatchers breed and forage near the shoreline, they're highly vulnerable to oil spills.
Monogamous pairs make their nests by tossing rock flakes, pebbles or shell fragments toward their nest bowl with a sideways or backward flip of their bills. They use the same nest year after year.
Limpets and mussels have a strong muscle that holds the two shells tightly together—yet an oystercatcher can easily and quickly pry them open. The birds also sneak up on open mussels, quickly stab their beaks between the shells, sever the muscle, shake the mussel free and swallow it. With sharp jabs of their bill tips, oystercatchers dislodge limpets and chitons from rocks, turn them over and eat the soft tissue.
Because the Aquarium's black oystercatcher was raised in captivity, she never learned to open shells on her own. We give her shelled clams and fish that are ready to eat.