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Purple Sandpiper Life History

Habitat

Habitat Shorelines

Purple Sandpipers nest on arctic tundra, including stony plateaus, moorlands, upland ridges, and wetter lowlands. Drier areas feature lichen, bilberry, crowberry, and birch; wetter areas often have hummocks and mosses. Other Purple Sandpipers nest in tundra along coastal beaches or on shingle or gravel-sand beaches along rivers and streams. During the breeding season, they forage mostly in wet tundra and in tidal areas, especially where there are rocky shorelines or islands. Migrants stop at rocky areas along coastlines. They're not often seen inland on migration, but they are sometimes reported from rocky edges (natural or artificial) of bays, lakes, and rivers. Small numbers winter on rocky, unfrozen portions of the Niagara River. Most of the population winters along rocky marine shorelines and islands farther north than other shorebirds. They forage and roost among rocks, sometimes sheltering from severe storms in nearby harbors, bays, or grassy island interiors). Spring migrants often use muddy or sandy shorelines, especially where there is wrack containing invertebrate prey.

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Food

Food Aquatic invertebrates

Purple Sandpipers eat mostly invertebrates. They spend most of the year on rocky shorelines, eating creatures unfamiliar to most people such as mussels, periwinkles, sea snails, worms, and small crabs and other crustaceans. —and indeed many of their prey items have only scientific names. They stand or walk slowly on rocks, searching for prey visually or simply inserting the bill into algae or wrack to detect prey by touch or taste. Often, they probe between barnacles or mussels for small prey items, but they also eat small mussels whole, grinding the shells in the gizzard. Purple Sandpipers sometimes flip over seaweed or wrack to search for prey, much as turnstones do. They forage more on falling and lower tides than at high tide, and they often forage at night, even in the middle of winter. Many of their prey species live among marine algae, and Purple Sandpipers consume a fair amount of this algae as well. When foraging along shorelines in wrack, they eat larval and adult kelp flies and other flies. On the breeding grounds, at least when they forage in marine environments, their diet is similar to the nonbreeding season. On the tundra, especially in the highlands, they consume spiders, worms, aphids, beetles, springtails, and flies of many different families. Their foraging in the tundra is mostly by picking and probing with the bill into lichen, soil, and sometimes into snow and ice. They also eat seeds, berries, leaves, and buds of Arctic plants.

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Nesting

Nest Placement

Nest Ground

The male makes several scrapes in tundra and shows them to the female. She selects the final site, a ground site in tundra with sufficient brushy cover to conceal the nest.

Nest Description

Nest is set into a scrape or depression, roughly cup-shaped, lined with feathers, sedges, and leaves of willow, mountain avens, or arctic bell-heather. Nests average about 3.7 inches across and 1.3 inches tall, with interior cup 1 inch deep.

Nesting Facts

Clutch Size:3-4 eggs
Egg Description:

Beige to olive, with variable spotting.

Condition at Hatching:

Completely covered with dense white down. Capable of walking and pecking at ground within a few hours of hatching.

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Behavior

Behavior Probing

Male Purple Sandpipers begin territorial displays shortly after returning to the breeding areas, in early June, often when the tundra is still locked in snow and ice. Male courtship includes a flight display, chasing females over the ground with one wing is raised, and scraping at the ground as if starting a nest. The flight display is memorable: males rise high above the territory and circle slowly, delivering a rollicking song as they alternately flutter the wings rapidly and glide on stiff wings. In long-term studies conducted in Europe, researchers have discovered that Purple Sandpipers are long-lived, monogamous, and mate for life. DNA studies confirm the monogamy and indicate there's very little “extra-pair copulation.” Both sexes share incubation duties, but females depart the territory just as the eggs begin to hatch, leaving males to raise the chicks to fledging. This arrangement is unique among shorebird species that share incubation duties. Long-term studies also reveal that males return to their same territories year after year. During migration and on wintering grounds, Purple Sandpipers are relatively social with others of their species and with other shorebirds such as Ruddy Turnstones and Sanderlings. Their habitat probably limits flock sizes, which range from a few birds to a few hundred at most.

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Conservation

Conservation Restricted Range

As is true of most bird species that nest in the high latitudes, there are no North American Breeding Bird Survey estimates for Purple Sandpiper population trends. A 2012 study estimated the North American population at 25,000 and noted that populations appear to be declining. Partners in Flight estimates a global breeding population (including a large range in Europe) of 250,000 birds, rates the species a 14 out of 20 on the Continental Concern Score, and includes Purple Sandpiper on the Yellow Watch List for species with restricted ranges. Threats to the survival of this species include pesticide poisoning (known to be a problem in this species), oil spills, oil pollution, and climate change—the rise of sea levels will reduce foraging habitat, and the encroachment of shrubs into tundra will reduce nesting habitat.

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Credits

Andres, B. A., P. A. Smith, R. I. G. Morrison, C. L. Gratto-Trevor, S. C. Brown, and C. A. Friis (2012). Population estimates of North American shorebirds, 2012. Wader Study Group Bulletin 119:178–194.

Partners in Flight (2017). Avian Conservation Assessment Database. 2017.

Payne, Laura X. and Elin P. Pierce. (2002). Purple Sandpiper (Calidris maritima), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.

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