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May 6, 2019 10:43 AMPublication: The East Hampton Press & The Southampton Press

A Walk On The Beach

Sanderlings in a frenzy feeding on beach fleas. MIKE BOTTINI
May 6, 2019 11:34 AM

During a visit to any of our ocean beaches this month, you are likely to encounter one or more small flocks of sanderlings (Calidris alba). This small, plump, energetic shorebird spends most of its time running up and down the intertidal zone just out of reach of the frothy swash generated by breaking waves, and jabbing its short, stout bill into the soft sand in search of suitable prey hidden from view.This feeding behavior relies on sensitive nerves and chemoreceptors located in its bill. Researchers have determined that the sanderling relies on its sense of touch more than any other, locating its favored prey by feeling for them in the wet sand. Among their favored prey residing in the swash zone here are mole crabs. Along with the shelled meat, a fair bit of sand is ingested, and this indigestible material is coughed up in the form of a pellet, much like owls and hawks cough up indigestible feathers and bones.

Last week’s particularly frenzied feeding behavior by a flock numbering several hundred sanderlings had me curious as to what they were catching in the swash zone. Running my fingers through the wet sand revealed tiny, one-eighth-inch-long, shrimp-like creatures. These are a type of amphipod commonly known as sand hoppers or beach fleas. They reside on the upper beach, in the intertidal zone, under the wrack line, and in shallow water, and they are difficult to key out to species.

Even though they don’t nest here, sanderlings can be found on Long Island’s beaches any day of the year. They are not ready to breed and nest until age 2, and some of the 1-year-olds will spend their first summer here. The big flocks of mature birds will move through our area this month, stopping to refuel en route to their Arctic nesting grounds from overwintering sites as far south as Tierra del Fuego.

Among the population of sanderlings that migrate north along the eastern seaboard in spring, Delaware Bay is a very important stopover. Their arrival on the shores of that large estuary is closely synchronized with the peak in horseshoe crab mating and egg laying. An estimated 39,000 sanderlings will remain at Delaware Bay for three weeks, with each bird consuming an average of 13,000 eggs per day! That works out to 10.6 billion eggs consumed.

From Delaware Bay, most sanderlings fly the remaining 4,000 km (2,400 miles) non-stop to their Arctic nesting grounds in two to three days. The 4,000 km distance happens to coincide with their maximum estimated flight range without refueling, and the sanderling is one of several wildlife species that will benefit from efforts to protect the horseshoe crab and limit development of Delaware Bay’s coastline.

Their nesting window is a tight one, as sanderling adults begin making the return trip south and arrive on our Long Island beaches in late July, with the largest waves of adults showing up in August. Juveniles generally begin arriving here in late August, but most fly in during the months of September and October. The adults and juveniles can be distinguished from one another by the darker, mottled black and white colored pattern found on the latter’s back and wings. Adults still sporting their breeding plumage have a distinctive rufous head and neck which is replaced by a very pale gray, come fall.

Researchers have noted a significant decline in sanderling numbers on the East Coast of North America, but the reason for those declines is uncertain. North America’s sanderling population is estimated to be 300,000 birds, with 70,000 breeding pairs nesting in the Canadian and Alaskan Arctic. It is considered the most widespread maritime shorebird wintering in North America, with small winter populations scattered from British Columbia and Maine, south to Chile and Argentina. They also nest in the Arctic regions of Greenland, Norway and Russia, with those populations wintering on the coasts of Europe, Africa, Australia, Asia and even Hawaii and the Galapagos Islands.

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