A birder found a White-rumped Sandpiper in Edmonds Marsh on June 1. It is a shorebird that had never been reported in Edmonds in the 30-plus years of modern recordkeeping. Word went out to state birders and many visitors arrived to see this one-day rarity. It is the 278th species that we have documented in Edmonds. Among Western Hemisphere shorebirds, it is one of the latest spring migrants. Late May and early June are expected dates for this shorebird to fly north through the U.S.
The White-rumped Sandpiper makes one of the longest migrations in the Western Hemisphere. It winters at the southern extremities of South America, including coastal Argentina and Uruguay. It breeds on Canada’s Arctic islands and along the north coast of Alaska. This shorebird’s long wings are a clue to its long migrations. Its flight path through North America is from the Texas Gulf Coast to Florida and north along the Great Plains and the eastern state/provinces of the U.S. and Canada. This species rarely comes west. When it migrates back to its wintering grounds, it mostly flies over the Atlantic without stopping to northern South America or passes over the continental U.S. It can fly for up to 60 hours without stopping and cover up to 4,000 kilometers.
During migration the White-rumped Sandpiper can be found in flooded fields, shallow ponds, edges of freshwater marshes, tidal flats and gravel beaches. It breeds on low-lying wet tundra with grassy areas and dwarf willows. Little is known about its wintering grounds. Its diet includes insects, mollusks, marine worms and seeds. It probes in mud for prey and picks some items, such as seeds, from the surface. On tundra it probes deeply into moss and other vegetation for its food. The bird at Edmonds marsh was observed probing in the mud for food similar to other sandpipers.
Courtship displays of the male include gliding and fluttering over its breeding territory while making oinking and rattling sounds. On the ground the male will stretch out his wings and raise his tail high enough to show off his white rump patch. He then gives repeated calls while walking and running. The nest site is on the ground, well hidden in a clump of grass or moss on the tundra. Female builds a nest that is a cup-shaped depression lined with lichen, moss and leaves. She then incubates the four eggs for about three weeks.
Downy young chicks leave the nest a day after hatching. The female tends them and broods them to keep them warm, but they forage for their own food. The young birds take their first flight a little more than two weeks after hatching.
Little is known about life span, survivorship, and causes of mortality of the White-rumped Sandpiper. It is a species awaiting further research. There are many collective nouns for a group of any sandpipers. They include bind, contradiction, fling, hill, and time-step.
It is difficult to estimate the population of the White-rumped Sandpiper. Numbers are available for several Canadian Islands that host major nesting sites. Surveys of spring migration stopovers at Decatur, AL, and Cheyenne Bottoms, KS, in 1991 indicated 30,000 – 40,000 birds. It was thought that this represented a significant percentage of the breeding population. Large numbers of this shorebird species were once shot in North America for human consumption. This no longer occurs. There is no research on the impact of pesticides on the population. It is probably most vulnerable to diminished habitat in the U.S. where it rests and fattens up for its flight to the Arctic breeding grounds. Preservation of Great Plains wetlands is key to healthy populations of all shorebirds using the Central Flyway, including the White-rumped Sandpiper.
Flight calls from a flock of White-rumped Sandpipers can be heard here: www.xeno-canto.org/147084.
— By Carol Riddell
Carol Riddell manages the bird education displays, on behalf of Pilchuck Audubon Society and Edmonds Parks & Recreation, at the Olympic Beach Visitor Station.