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Sanderling

Calidris alba ORDER: CHARADRIIFORMES FAMILY: SCOLOPACIDAE

IUCN Conservation Status: Least Concern

The Sanderling’s black legs blur as it runs back and forth on the beach, picking or probing for tiny prey in the wet sand left by receding waves. Sanderlings are medium-sized “peep” sandpipers recognizable by their pale nonbreeding plumage, black legs and bill, and obsessive wave-chasing habits. Learn this species, and you’ll have an aid in sorting out less common shorebirds. These extreme long-distance migrants breed only on High Arctic tundra, but during the winter they live on most of the sandy beaches of the world.

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At a GlanceHelp

Measurements
Both Sexes
Length
7.1–7.9 in
18–20 cm
Wingspan
13.8 in
35 cm
Weight
1.4–3.5 oz
40–100 g
Relative Size
About the same size as a Dunlin. Smaller than a Red Knot; larger than a Least Sandpiper.
Other Names
  • Bécasseau sanderling (French)
  • Playero blanco (Spanish)

Cool Facts

  • The Sanderling is one of the world’s most widespread shorebirds. Though they nest only in the High Arctic, in fall and winter you can find them on nearly all temperate and tropical sandy beaches throughout the world. The Ruddy Turnstone and the Whimbrel are the only other shorebirds that rival its worldwide distribution.
  • The Sanderling’s mating system varies from area to area and possibly from year to year. Sanderlings are usually monogamous, but in some cases the female breeds with multiple males in a row within a single breeding season.
  • Nonbreeding Sanderlings often stay on the wintering grounds through the summer, saving energy by avoiding the long trip to the Arctic nesting grounds. Many nonbreeders remain in South America, while fewer remain along the North American coasts.
  • When threatened by a Peregrine Falcon, Sanderlings fly in a compact flock that maneuvers erratically over the ocean. Whenever you see a flock of shorebirds abruptly take flight all at once, scan the skies to see if a falcon is the cause of the sudden alarm. In their escapes, individual Sanderlings may occasionally dive right into the water.
  • After foraging on the beach, Sanderlings often regurgitate sand pellets studded with fragments of mollusk and crustacean shells.
  • The oldest Sanderling on record was at least 13 years, 1 month old.

Habitat


Shore-line

Sanderlings breed in the tundra of High Arctic Canadian islands and peninsulas, and rarely in Alaska. Their nesting habitat ranges from moist sites with lots of vegetation to well-drained clay or gravel slopes, to the tops of stony ridges; it often includes arctic willows, sedges, heathers, purple saxifrage, and mountain avens. While migrating along the North American coast, Sanderlings stop on hard-packed sand beaches, tidal mudflats, rocky coastlines, and inland bodies of water—including ponds, streams, reservoirs, and shallow prairie lakes. They spend the winter on sandy beaches all over the world; some stop as far north as southern Alaska, Nova Scotia, and Newfoundland while others go the length of South America. Less commonly, they may winter on mudflats, lakeshores, and riversides.

Food


Insects

Sanderlings feed by running down the beach after a receding wave to pick up stranded invertebrates or probe for prey hidden in the wet sand. Its diet includes small crabs, amphipods and other small crustaceans, polychaete worms, mollusks, and horseshoe crab eggs. Sanderlings may also skim food from shallow pools while running, pick up moving prey on the ground, or—during the summertime—snap at flying insects. They eat crane flies, midges, mosquitoes, beetles, butterflies, and moths. When no animal prey is available, Sanderlings eat plant material, including saxifrage buds and shoots, roots, grass seeds, algae, and mosses.

Nesting

Nesting Facts
Clutch Size
3–4 eggs
Number of Broods
1 broods
Egg Length
1.3–1.5 in
3.3–3.8 cm
Egg Width
0.9–1 in
2.4–2.6 cm
Incubation Period
23–27 days
Nestling Period
1 days
Egg Description
Dull green to olive-brown or greenish-blue), marked with brown spots and blackish streaks.
Condition at Hatching
Well-developed and downy, with dark legs and bill and black eyes.
Nest Description

The nest is probably built by the female alone. She forms a shallow, cup-shaped hollow in the stony ground and lines it sparsely with willow leaves, saxifrage leaves, lichens, bits of moss, and occasionally dry willow twigs and pebbles. It measures about 3 inches across and 2.5 inches deep.

Nest Placement

Ground

The female chooses a nest site near the shores of a freshwater lake or pond. The nest is placed on the ground in an exposed location with little or no vegetation, often at a pre-existing depression.

Behavior


Probing

On beaches, Sanderlings are strong, fast runners as they perpetually scurry just ahead of arriving and retreating waves. On the nesting grounds males establish territories about 400 yards across, and both members of a breeding pair chase intruders from the territory. Sanderlings are mostly monogamous, but their mating system may differ from area to area and year to year. Males (and, less frequently, females) perform aerial displays before mating. The bird alternately flutters and glides in an erratic path in an area about 200 yards wide, dipping low to the ground and rising to 30 feet high or more while vocalizing; these displays can last 2 minutes. After pairing, the two birds accompany each other everywhere. Studies in Canada have found that females sometimes mate with multiple males in sequence when conditions are favorable. Both sexes incubate. When confronted with a predator, incubating parents freeze on the nest until the last second, when they creep away from the nest while feigning injury. Nest predators include Parasitic Jaegers, Long-tailed Jaegers, Glaucous Gulls, Snowy Owls, artic foxes, and wolves. During migration and winter Sanderlings may flock with other small shorebirds such as Dunlins, Red Knots, Black-bellied Plovers, Willets, Short-billed Dowitchers, Long-billed Dowitchers, Ruddy Turnstones, Semipalmated Sandpipers, and Western Sandpipers. They roost on beaches in closely packed flocks of up to several thousand birds, standing or squatting against the wind and jostling for the least exposed positions in the flock. When threatened by an avian predator such as a falcon, Sanderlings take flight and form a tight ball that careens erratically over the ocean.

Conservation

status via IUCN

Least Concern

Although Sanderlings are one of our most common shorebirds, their populations are declining and they are listed as a species of high concern by the Western Hemisphere Shorebird Reserve Network. The world population is estimated at about 700,000 individuals, with about 300,000 occurring in the Americas. Shorebird population sizes are difficult to estimate because the birds cluster in large flocks scattered over large distances. However, surveys suggest that Sanderling populations are declining, sharply in places. According to Christmas Bird Counts, there was an overall decrease of 0.5 percent per year between 1959 and 1988, and California counts decreased by 3.7 percent per year. From 1974 to 1982, Sanderlings on the Atlantic Coast dropped by 13.7 percent per year. In that time, peak migration counts in Massachusetts dropped from 10,000-30,000 birds in the 1950s to an average of just 2,000 birds. Declines are probably caused by development or alteration of shoreline habitats—the sandy beaches Sanderlings live on are also prized by humans for recreation. Sanderlings are also vulnerable to pollution from pesticides and, especially, oil spills due to their close association with the ocean edge. In some areas, notably Chesapeake Bay where there has been a large fishery for horseshoe crab eggs, humans compete with Sanderlings and other shorebirds for food. Conservation of long-distance migrants like Sanderlings is always complicated because of the birds’ reliance on distantly separated staging areas, which have to provide enough food at the right time, and which are all subject to their own habitat pressures.

Credits

Range Map Help

Sanderling Range Map
View dynamic map of eBird sightings

Migration

Long-distance migrant. Some Sanderlings travel as few as 1,800 miles to coastal New England, while others fly more than 6,000 miles to temperate South America. Even individuals that winter on the same beach can take different migration routes and may end up on different breeding grounds.

Find This Bird

Sanderlings are easy to find on sandy beaches from fall through spring. Pick a beach with a low, gradual slope and walk along the water’s edge. Look for small shorebirds running back and forth in sync with the waves—these are likely to be Sanderlings. While other shorebirds such as plovers and Willets may feed alongside Sanderlings on these outer beaches, this is truly the Sanderling’s domain; these plucky birds often aggressively defend their feeding territories at water’s edge from other shorebirds.