Bird of the Month: Rock Sandpiper
By Andy McCormick
PC: Mick Thompson (Rock Sandpiper)
Scientific Name: Calidris ptilocnemis
Length 9 in
Wingspan 17 in
Weight 2.5 oz
AOU Band code ROSA
The Rock Sandpiper is one of Washington’s wintering shorebirds. It is seen with some regularity along the jetties at Westport and Brown’s Point in Ocean Shores, most often in the company of Surfbirds, Ruddy Turnstones and Black Turnstones, which also forage on rocky shores. It arrives in October and is active through the winter specializing in the splash zone of algae-covered intertidal habitat. It is thought that they will forage more at low tide even during nocturnal low tides (Gil, et al).
They are very similar to and could be considered a western counterpart of the eastern Purple Sandpiper, which also spends much of its time on rocky shores (Alderfer). The Rock Sandpiper winters farther north than any other shorebird with most birds wintering around Cook’s Inlet in Alaska. However, some migrate regularly as far south as northern California.
The Rock Sandpiper is one of the “rockpipers” and is found almost exclusively along rocky shores. It is a member of the large Calidris genus, from the Greek kalidris, used by Aristotle for a speckled waterbird. Its species name ptilocnemis is from the Greek ptilon, a feather, and knemides, armor worn over the shins, referring to soft feathers over the upper part of the leg. This feathering cannot be seen well in the field, and this information is not helpful as a field mark for identification.
Much more helpful for identification in Washington is the bird’s size, which is similar to a Dunlin, and its location on rocks near waves. During breeding season in Alaska, some care must be used regarding location, because some subspecies of Rock Sandpiper will forage on tidal flats. The bird can be separated from the Surfbird by its longer and more drooping bill and the lack of the Surfbird’s white rump (Alderfer).
Rock Sandpipers breed in mossy tundra close to the Yukon River Delta at the Bering Sea and along the Aleutian Islands (Gil, et al). The nest is often on a raised area of moss or grass. A scrape is made by the male and the female deposits four olive- to buff-colored eggs which have brown blotches. Both parents incubate the eggs for about 20 days, but after hatching they are cared for only by the male. Hatchlings leave the nest in about three days and forage for their own food. There is not enough data to know when first flight occurs with any accuracy. In general, Rock Sandpipers eat crustaceans, mollusks, marine worms and unlike most other sandpipers, some plant material such as algae, moss, berries and seeds.
The world population of Rock Sandpipers is around 100,000 individuals. The population has been declining since the 1970s (Kaufman). It is considered a Watch List bird of the Highest Concern (Lebbin, et al). The concern is related to its restricted breeding range and potential adverse effects to its limited wintering sites.