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recent trip to the West Beach area of Deception Pass State Park (DPSP) gave me the opportunity to spot one of my favorite shorebird species, the black oystercatcher. With its long flaming red-orange bill, each bright yellow eye highlighted by a red eye ring, and bizarrely pink legs and feet, it’s pretty hard to mistake them for any other species. Even their strident “wheep wheep” calls are distinctive from those of other shorebirds.
Up until about three hundred years ago, oystercatchers were commonly called “sea pies”. Around that time American oystercatchers were observed feeding on small East Coast shellfish called “coon oysters”, and from that they were tagged with what later became accepted as the common name. The scientific name, Haematopus bachmani was assigned to them by the artist John James Audubon. The genus name Haematopus is derived from Greek words meaning “blood foot” and the species name honored his friend John Bachman. Audubon also painted this species as part of his Birds of America collection (http://www.audubon.org/birds-of-america/white-legged-oyster-catcher-or-slender-billed-oyster-catcher).
Young oystercatchers can be distinguished from mature birds by the dusky tint on the end of their bill, a more brownish cast to their feathers, and a dull brownish or yellowish coloration on their legs. Adult females are slightly larger than males and their bill is slightly longer than those of adult males.
Perched on those massive up-thrust chunks of West Beach bedrock, these birds were in their element; black oystercatchers are most at home on rocky shorelines. Present year-round on Salish sea beaches, the crow-sized birds are usually seen in pairs or small flocks. During high tide they like to perch and rest, often tucking their bill back underneath one wing.
Low tide finds the black oystercatcher skimming low across the surface of the water to rocky intertidal areas where they forage for food. In many areas their favorite prey items are limpets and mussels. The oystercatcher’s bill is the perfect tool for prying limpets off rocks and slipping between mussel valves to clip the adductor muscles allowing them to access the tasty flesh. Their well-adapted bill also gives them the option of hammering a hole into a mussel shell to get to the nutrients inside. They consume only the meat leaving the shells behind. One resource estimated that an oystercatcher may consume 100 lb. of mussel meat a year. It has been observed that these birds take about 45 seconds to get into a mussel while take down time for a limpet is only 10 seconds.
Black oystercatchers also prey on acorn barnacles, sea urchins, polychaete and peanut worms, periwinkle and Nucella snails, black katy, lined, and Mopalia chitons, isopods, and small crabs. Although we sometimes forget that birds impact the beach habitat, black oystercatchers have been shown to affect prevalence of intertidal algae and invertebrates on beaches where they feed.
Whidbey and Camano Islands are not hotbeds for oystercatcher nesting so beach naturalist volunteers at Rosario Beach have for many years counted themselves fortunate indeed to have the opportunity to watch a pair that nests on Urchin Rocks. Sammye Kempbell a Sound Water Steward volunteer and long-time Beach naturalist at DPSP tells me that this spring they raised one apparently healthy and very demanding baby.
When the tide is high, the offshore rocks at the north end of DPSP West Beach area are a good place to view black oystercatchers and we have also seen them on the Keystone Jetty. Sarah Schmidt reminds us that another great birding observation point with good odds for sighting black oystercatchers is from the Hastie Lake Boat Ramp parking area when the tide is low enough to expose the rocky shoreline. Any rocky beach area with an abundance of barnacles, mussels, and other small invertebrates should be good foraging areas for them. Keep a look out for any banded black oystercatchers and if you spot one, try to get a good look at any identifying marks on the band. That information should be reported to Ruth Milner at Washington Dept. of Fish and Wildlife (Ruth.Milner@dfw.wa.gov).
Find out more about this fascinating bird at
http://www.marineornithology.org/PDF/37_1/37_1_29-32.pdf
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