SANDERLINGS - BIRDS OF THE BEACH

Across the lonely beach we flit,

One little sandpiper and I,

And fast I gather, bit by bit,

The scattered drift-wood, bleached and dry.

The wild waves reach their hands for it,

The wild wind raves, the tide runs high,

And up and down the beach we flit,

One little sandpiper and I.

From The Sandpiper, by Celia Thaxter, 1883

Thaxter's writing about the poem makes it clear that its source was an encounter with a plover near its nest, but her description makes it sound as if she was watching a Sanderling (Calidris alba), the most common sandpiper on open ocean beaches almost anywhere in the world. Had it been a Sanderling, she would have marveled at its hyperactivity as it charged the ocean waves and then retreated as the waves charged back.

Sanderlings are particularly common on the Pacific Northwest coast, where the richness of the ocean waters enhances the productivity of the intertidal zone. The only higher densities recorded for the species in the Americas in winter are along the Humboldt Current beaches of Peru and Chile. Flocks of hundreds of birds occur all along our outer beaches, and they are tame enough (and presumably used to crowds of people) that you can watch their foraging behavior at great length.

Sanderlings dash in and out of the waves to get prey exposed by the receding water, but they also spend much time above the waves running around on either dry or wet sand. Like many other sandpipers, they can find their prey either visually or tactilely.

Tactile foraging involves plunging their slightly opened bill into the sand at frequent intervals as they run, like an animated sewing machine, to search for prey. When a prey item is felt, the bill tip closes on it and extracts it from the sand. Sanderlings foraging like this leave characteristic series of probe holes.

When foraging visually, a Sanderling moves just as rapidly and must have superb vision to see the tiny prey items that it seeks. Many amphipod crustaceans are taken this way, but some days they seem to be hunting thin worms, polychaetes of the family Capitellidae. This prey item is not mentioned in the most recent account of Sanderling natural history, yet all birds appeared to be feeding on them on a recent February visit to Long Beach, Washington.

A bird would move rapidly along, then suddenly stop and grab an incredibly thin worm and pull it quickly from the substrate. It would swallow it in a few gulps, sometimes running off while doing so. Birds were crisscrossing in front of us constantly, presumably spaced out to avoid direct competition for a single prey item. Hundreds of worms were being consumed, but I am sure there were many more where those came from.

Dennis Paulson

SHOREBIRDS ON THE MOVE

Every spring, about the beginning of April, flocks of shorebirds begin their annual migration up the Pacific coast on their way to Alaska and other points north. Sandpipers and plovers by the tens of thousands use the coastline as a pathway to their summer homes, feeding on the abundant populations of marine invertebrates and depositing fat to fuel their long-distance flights to their breeding grounds. Some birds leave the Washington coast and fly directly across the Gulf of Alaska to southern Alaska, where they stop at estuaries such as the Copper River Delta.

The most common species are Western Sandpipers, Dunlins, and Short-billed Dowitchers, in that order. At the same beaches, mudflats, and tidal pools are smaller but still substantial numbers of Black-bellied and Semipalmated Plovers, Greater Yellowlegs, Whimbrels, Marbled Godwits, Ruddy Turnstones, Red Knots, Sanderlings, Least Sandpipers, and Long-billed Dowitchers. At the same time, Black Turnstones, Surfbirds, and Wandering Tattlers feed along rocky shores as they move north, and Red-necked and Red Phalarope flocks settle on the ocean offshore.

These birds take advantage of a spring flush of invertebrate growth and recruitment, and they find no lack of goodies to help them put on weight. Amphipod crustaceans, polychaete worms, and small bivalves are among the most abundant fauna in birds that feed on and in sand and mud. These animals are so abundant that just about all the shorebird species using the area feed on them. Barnacles, mussels, and snails are staples of the rock shorebirds, and planktonic crustaceans fill the bellies of phalaropes.

Shorebird migration peaks on the Washington coast in the last week of April and first week of May, when the maximum number of species and individuals are present. Grays Harbor and Willapa Bay and the beaches adjacent to them always support the largest numbers, and the abundance of these birds provides a stirring spectacle every spring. Concentrations of some species in Grays Harbor are the highest south of Alaska.

And there is a Grays Harbor Shorebird Festival every spring to enjoy these concentrations: http://www.shorebirdfestival.com/.

Unfortunately, shorebird numbers have been declining, so the spectacle gets a little less spectacular every year. More importantly, we don’t have a good handle on the cause of the decline. Presumably it relates to loss of habitat on either the wintering grounds or at migration stopovers, as the arctic and subarctic breeding habitats are still relatively intact.

It’s also possible that anthropogenic changes are reducing the abundance of shorebird prey, another factor that we don’t know much about on a grand scale. There are still lots of shorebirds, so we have some time to work out an effective conservation plan, and there is such a plan for the U.S. (http://www.fws.gov/shorebirdplan/).

Dennis Paulson