by Frank Keim
This is a lookalike bird if I ever saw one. Which might explain why the bird’s Yup’ik names are the same as those used for the Western and Least sandpipers: Iisuraar(aq) and Iiyuraar(aq). Their meanings are the same, too: “the dear little thing that makes the sound iisur (Scammon Bay-Yukon River) or iiyur (Hooper Bay-Chevak).” And while we’re on names, the scientific name, Calidris pusilla means “very small shorebird.” The genus name is from the ancient Greek kalidris, a term used by Aristotle to describe some gray-colored waterside birds. Pusilla is Latin for “very small.” The bird gets its common name from the short webs between its toes (“palmated” means webbed). Its cousin the Western sandpiper is the only other small sandpiper with webbed toes. Both of these birds belong to a group of small sandpipers commonly known as “peeps.”
After the males return to the Y-K Delta sometime in May from their tropical wintering grounds in South America, they immediately claim their nesting grounds. By the time the females arrive several days later, even before the snow has melted completely, the males have chosen their territories and have begun to defend them. They often return to the same territories they had the previous spring and defend them with hovering display flights, fluttering their wings and singing a sputtering trill that sounds a little like a toy outboard motor (as described above in their Yup’ik name).
These tiny shorebirds nest in tundra, not far from marshes or ponds that include a mix of shallow water sedges, rushes and grasses, plus mosses, willows, birch, and berry plants. This nesting habitat includes all of the foods they need to breed and raise young: tiny invertebrates, including insects, spiders and aquatic animals such as small crustaceans, mollusks, and marine worms. They feed both visually and by touch, pecking and probing rapidly at the surface with repeated jabs of the bill. Their sharp vision and the sensitivity of their bill tips allow them to also forage at night. Other foods include algae and small crab eggs. Since females have larger bills than males, they can take larger prey, a necessary evolutionary feature since females produce the eggs.
Semipalmated sandpipers seem to be monogamous for longer than a year. When a female shows an interest in a male, who is often her previous year’s mate, a courtship display ensues where the two birds chase each other, call, cock their tails, and make paired flights. Displaying males raise one or both wings, erect their crown feathers, and lead females to multiple nest scrapes they have made beforehand, usually on a small hummock near a pond surrounded by low willow, grass or sedge plant cover. Males guard the females closely until they’ve laid their clutch of eggs, and are very territorial through the chick-rearing period.
After selecting one of her mate’s nest scrapes for use, the female lines it with grass, sedges, moss, and leaves, then usually lays 4 eggs that are whitish to olive-buff, blotched with brown and gray. Both parents help with the incubation of the eggs for about 20 days, and after hatching, the downy young leave the nest within just a few hours. They already know how to feed themselves but learn new survival strategies from both of their parents who tend them for the first few days, after which the mother bird leaves and their father takes over parenting duties until they are old enough to fly. The young can make short flights at about two weeks, and can fly fairly well at 16-19 days old. From then on, they’re on their own.
In preparation for migration, the young fatten up on the same fare as their parents, then gather in large flocks in shallow-water mudflats. While still young, both male and female Iisuraarat are as territorial as adult birds all year-round, and even during migration and on their wintering grounds they endlessly chase off other birds if they approach too closely. Since dominance is decided by size rather than age, their dominance hierarchies become more rigid as they continue feeding on their way south through the central and eastern American states towards their winter habitat in South America. En route, they stop over at coastal beaches, sandbars, tidal mudflats, and temporary wetlands. Studies have shown that in late fall they make a non-stop flight of nearly 2000 miles from New England or eastern Canada to the South American coast.
On their tropical wintering grounds, they mainly use tidal mudflats near river mouths flowing into estuaries and bays. Among migratory birds, the Semipalmated sandpiper is in no hurry to migrate north in the spring, since one-year olds mostly stay in South America until the next year when they begin moving north.
At present, these birds are still abundant, although numbers have declined in recent years partly because of hunting in South America, the destruction of wetlands, and the increasing presence of environmental pollutants everywhere. Climate change, including sea level rise, is also expected to have negative effects on their nesting areas in the north, as well as on their migratory stopover sites and wintering grounds.
