(c) Glen Tepke
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The Rock Sandpiper is a sturdy shorebird of the northern Pacific coast. Where the surf washes nutrients over rocky shores and gravel banks, the Rock Sandpiper thrives in frigid temperatures, in areas with short winter and long summer days. The sandpiper's species name, "ptilocnemis," means "feather boot" and describes one of its adaptations to the cold—protective feathers covering the leg down to the heel.
The Rock Sandpiper averages 9 inches in length with a 17-inch wingspan, and weighs approximately 2.5 ounces. This small to medium-sized sandpiper has a stout build and dark grey plumage in winter. Only the under-wing, vent, and lower belly are white. The dark bill is moderately long and slightly drooped, with a yellow-green base. The stout legs are yellowish in winter. Rock and Purple Sandpipers are so similar in winter plumage that separation is extremely difficult. However, they reside on opposite coasts. Also, unlike its sister species, breeding Rock Sandpipers present a black patch on the belly.
The Rock Sandpiper breeds in Alaska from the Aleutian Islands to the Seward Peninsula, and in Russia, on the Chukotsky and Kamchatka Peninsulas. In North America, populations winter coastally from northern California to the Aleutian Islands. Rock Sandpipers are fairly uncommon in the United States and Canada.
A legend for the range map to the right can be found
here.
Rock Sandpipers breed on the Arctic tundra at low elevations and prefer short vegetation dominated by herbs, sedges, or small woody plants like crowberry. After breeding, this hardy shorebird moves to rocky beaches at river mouths, or to eroding river banks, often made of peat. Rock Sandpipers spend most of the winter on rocky shorelines in the intertidal zone.
Locating prey by sight, Rock Sandpipers peck items from snow, ice, rock, gravel, and algae. Probing thick material and combing through ooze and muddy water, Rock Sandpipers also forage by touch. Walking and sometimes running, this sandpiper feeds day and night to take advantage of the tidal bounty. Rock Sandpipers consume a wide variety of prey, including small barnacles, snails, marine worms, herring roe, flies, beetles, spiders, and diverse larvae.
Just before or after arriving on their breeding grounds, Rock Sandpipers form monogamous pairs, sometimes with mates from the previous year. Males establish territories and attract mates with flight displays that include undulating flights and extended hovering. Males confront each other with lifted wings, parallel runs or flights, and crouching postures. Pairs court around dummy nests, where females inspect, enter, and rearrange the structure. Nests consist of a scrape, with a base of leaves, lichens, sedges, or mosses, often lined with finer plant materials.
The female lays four greenish eggs marked with brown, which hatch in approximately three weeks. One or both sexes may incubate the eggs. Chicks emerge precocial; within a few hours they can walk, feed, and hide. After a few days, they can keep themselves warm at night. Usually, the female departs before the young fledge, and the male stays on for guidance and defense. Parental defenses of the nest and young include hiding, running like a mouse, squealing, bleating, and faking injury. Juveniles fledge in about 23 days.
Sometimes in the company of other shorebirds like Dunlin and Black Turnstones, Rock Sandpipers migrate short to medium distances, in flocks numbering a few to thousands of individuals. Spring migration begins as early as March. Fall migration occurs in stages, with adults and juveniles often moving to secure inland areas to molt and gain weight as early as mid-July. Rock Sandpipers appear on the Pacific coast of Canada and Washington State from August through October.
Gill, R. E., P. S. Tomkovich, and B. J. McCaffery. 2002. Rock Sandpiper (
Calidris ptilocnemis). In
The Birds of North America, No. 686 (A. Poole and F. Gill, Eds.).
Kaufman, Kenn.
Lives of North American Birds. Houghton Mifflin Company, New York, 1996.
Sibley, David Allen.
The Sibley Guide to Birds. Alfred A. Knopf, New York, 2000.
