Introduction The black oystercatcher is the signature bird of the rocky intertidal coastline. It is a permanent resident on all five islands in the park, being restricted in its range, never straying far from shores and particularly favoring rocky shorelines. It has been suggested that this bird is seen mostly on coastal stretches which have some quieter embayments, such as jetty protected areas. It hunts through the intertidal area, searching for food visually, often so close to the water's edge it has to fly up to avoid crashing surf.
Quick and Cool Facts
Despite its name, this prominently-sized black bird with large feet seldom eats oysters.
Although they don't swim, black oystercatcher chicks will sometimes dive under water to avoid predators.
Migrating only short distances or not at all, they are permanent residents of their breeding range.
The black oystercatcher can live for more than15 years.
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 black oystercatcher has a very loud piercing whistle that can be heard at great distance over crashing waves.
Appearance The black oystercatcher is a distinctive, crow-sized, short-tailed, all-black shorebird. It has pale pinkish legs and a long, bright reddish-orange bill and eye-ring.
Range Oystercatchers breed from the western Aleutian Islands in Alaska south to central Baja, California. Within Alaska, they have ranged northward to the Pribilof Islands in winter and to RoundIsland, Bristol Bay, to nest in the summer. It is a permanent resident on all five islands in the park. Ranges of the black oystercatcher and the brown-and-white American oystercatcher overlap in Baja California.
Habitat Oystercatchers never stray far from shore and favor rocky shorelines in particular. It has been suggested that this bird is seen mostly on coastal stretches which have some quieter embayments, such as jetty protected areas.
Feeding Mussels and limpets are their primary food, but black oystercatchers prey on a wide range of shellfish and other creatures found along the rocky shore. They locate open mussels and disable them with a quick jab to the adductor muscle. With the mussel stuck in the open position, the oystercatcher can pull out the contents with the tip of its chisel-like bill. Oystercatchers often forage in the wave zone, because mussels that are splashed by waves open more frequently.
Reproduction The female black oystercatcher lays two to three eggs among pebbles in a shallow rocky depression or in a hollow on the beach above the high tide line. The nest is built by both the male and the female. They will create or scrape a depression in the ground and then pick up and toss shells and bits of rocks and pebbles into the depression with a backwards or sideways flip of their heads. They use the same nest year-after-year. Both the male and the female take turns incubating the eggs. The eggs incubate for 24-29 days and the chicks fledge in about 35 days. The chicks remain close to the nest at first. One of the parents will stay with them while the other parent forages for food to bring back to the nest. Eventually, the chicks will go with their parents to feeding areas. The chicks fledge at about five weeks and will forage on their own, but they will still occasionally be fed by their parents. The female has one brood a year.
Conservation Status The black oystercatcher, with a global population of 10,000-12,000 individuals, is considered rare. It is completely dependent on marine shorelines, favoring sheltered areas of high tidal variation that support limpets and mussels, their preferred food. Their numbers are highest from Alaska to British Columbia, where there is relatively plentiful preferred habitat and lower levels of disturbance than in the southern portion of the range.
The U.S. Fish & Wildlife Service selected the black oystercatcher as a Focal Species for Conservation Action due to small population size, restricted range, threats to preferred habitat, lack of baseline data to assess conservation status, and a suite of ongoing and anthropogenic and natural factors that may limit long-term viability. The U.S. Fish & Wildlife Service and other agencies in 2007 developed a range-wide conservation action plan and working group, which is the unified resource and blueprint for tracking and conserving the species.