White-rumped Sandpiper

(Calidris fusicollis) (WRSA)

Photographic Identification Guide

White-rumped Sandpiper (Calidris fusicollis) (WRSA), one of five species of small sandpipers referred to as “peeps” in North America, is among the longest-distance shorebird migrants. Breeding in northern Alaska and Canada, many migrate directly—sometimes with a few stops—to South America over the Atlantic Ocean. Most White-rumped Sandpipers winter in southern South America as far south as Tierra del Fuego.

In this guide, we cover the features, in order of importance, to look for on these birds. When discussing plumages, we use the terms winter, spring, and summer to refer to northern hemisphere seasons. Because some of these birds spend parts of the year in the northern and southern hemispheres, the correct technical terms for the plumage stages—basic and alternate—help avoid the confusion of seasonal terminology.

visual gallery

species account

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Fig. 1. White-rumped Sandpiper. Winter (basic) plumage. Note hooded appearance. Buenos Aires, Argentina. 21 March 2021.
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Fig. 2. White-rumped Sandpiper. Winter (basic) molting to spring (alternate) plumage. Note folded wings longer than tail. Tierra del Fuego, Argentina. 10 March 2023.
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Fig. 3. White-rumped Sandpiper. Spring (alternate) plumage. Note rusty scapulars. Anahuac National Wildlife Refuge, TX. 9 May 2015.
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Fig. 4. White-rumped Sandpiper. Spring (alternate) plumage. Note long, rangy profile. Bolivar Peninsula, TX. 11 May 2015.
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Fig. 5. White-rumped Sandpiper. Worn summer (alternate) plumage with very narrow margins. Winthrop Beach, Winthrop, MA. 3 September 2014.
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Fig. 6. White-rumped Sandpiper. Summer (alternate) molting to winter (basic) plumage results in salt-and-pepper appearance. Winthrop Beach, Winthrop, MA. 24 August 2015.
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Fig. 7. White-rumped Sandpiper. Juvenile plumage with dense, gray vermiculations (streaks) on breast. Winthrop Beach, Winthrop, MA. 18 October 2020.
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Fig. 8. White-rumped Sandpiper. Juvenile plumage. White rump is hardly ever visible on bird when not in flight. Winthrop Beach, Winthrop, MA.18 October 2020.
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Fig. 9. White-rumped Sandpiper. Juvenile molting to winter (basic) plumage. Cape May, NJ. 12 October 2021.
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Fig. 10. White-rumped Sandpiper. In flight, note overall gray-brown look. McKissack Beach, FL. 30 May 2023.
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Fig. 11. Comparison of juvenile Semipalmated Sandpiper and molting White-rumped Sandpiper. Nahant Beach, Nahant, MA. 2 September 2016.
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Fig. 12. Comparison of White-rumped and Semipalmated Sandpipers, both molting from summer (alternate) to winter (basic) plumage. Point of Pines, Revere, MA. 5 September 2011.
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Fig. 13. Comparison of molting adult White-rumped Sandpiper and molting juvenile Sanderling. Note similarity in size and browner, less contrasting plumage on White-rump. Plymouth Beach, Plymouth, MA. 23 September 20.
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Fig. 14. Comparison of three fall sandpipers: SESA juvenile; DUNL molting from summer (alternate); WRSA molting from summer (alternate). Note very long wings on WRSA. Winthrop Beach, Winthrop, MA. 16 October 2023.

The photos in this species account are arranged in this order:

Basic: winter plumage, roughly December to early March.

WRSA acquires winter (basic) plumage toward the end of the calendar year, usually when it approaches or arrives at its winter range. Basic-plumaged birds are mostly found south of the US border in winter; see Fig. 1.

Alternate: first spring and summer after hatch year or adult breeding plumage, March to October.

Beginning in spring, winter (basic) feathers on WRSA are gradually replaced by spring and summer (alternate) feathers; see Fig. 2. Most alternate feathers last until fall of the same year; see Fig. 4. Replacement by winter (basic) feathers begins in July or August; see Fig. 6.

Juvenile: young birds, recently hatched, August to October.

See Fig. 7, Fig 8. These feathers are acquired on the breeding grounds immediately after the natal down is shed and before the young begin their southbound migration.

Size and weight

Females are slightly larger and considerably longer-billed than males.

Body length:

7-7.3 in. (17.8-18.5 cm)

Wingspan:

16-18 in. (41-46 cm)

Bill length:

0.8–1.1 in. (20-27 mm)

Weight:

0.9-1.8 oz. (25-51 g)

Calls

WRSA calls are high-pitched, much higher than most other shorebirds. They are sometimes likened to pebbles clicking together. The song, primarily heard on the breeding grounds, is long and vigorous.

Calls in Puerto Hamburgo, Bolivia, 2013:

Calls in South Beach, Chatham, MA, 2010:

Plumage and other characteristics

The two larger peep sandpipers, White-rumped (WRSA) and Baird’s (BASA), are notably longer-winged than the three smaller peep species, Least, Semipalmated and Western Sandpipers. This is probably related to the much longer migrations undertaken by the two larger peeps.

WRSA wingtips project beyond the tail when the bird is on the ground; see Fig. 3, Fig. 6, Fig. 14.

In all plumages, WRSA is primarily gray and displays a hooded appearance due to the evenly streaked gray plumage on the head, neck and upper breast; see Fig. 4, Fig. 5, Fig. 12.

The gray hood emphasizes the usually conspicuous white eyeline (supercilium); see Fig. 1, Fig. 3, Fig. 8.

At close range, the breast on WRSA (particularly if juvenile) is evenly and narrowly streaked (vermiculated); see Fig. 7.

The white rump is conspicuous in flight; see Fig. 10. The white rump is occasionally discerned on birds on the ground, but it is usually covered by the wings; see Fig. 8.

In many individuals, especially in juveniles, the base of the lower mandible has a pale brown or reddish tint; see Fig. 7, Fig. 9.

WRSA in winter (basic) plumage has medium gray back (mantle) feathers, each with a central dark shaft. The belly is white with some flank streaking, and head and neck have pale gray streaking; see Fig. 1.

Beginning in spring, winter (basic) plumage is slowly replaced by spring (alternate) plumage; see Fig. 2. Fresh spring (alternate) feathers have broad blackish centers and wide gray margins.

On a breeding-aged bird in full spring (alternate) plumage, the back (mantle) is speckled dark and pale gray, usually with some rusty feathers on the upper scapulars. The crown and cheek are tinted pale buffy-brown with dark brown streaks. The nape, neck and upper breast are evenly streaked with gray, which thins out toward the belly. Some faint streaks or flecks continue on the flanks; see Fig. 3, Fig. 4.

Spring (alternate) and summer (alternate) are the same plumage; however, as seasons advance, feather margins become worn and the plumage looks different. In Fig. 5, note how the old back (mantle) feathers appear very dark because their broad pale gray margins have worn off.

Summer (alternate) plumage starts to molt to winter (basic) plumage by late summer and fall. WRSA displays a salt-and-pepper appearance as worn, dark, older feathers are replaced with new pale feathers with dark central shafts; see Fig. 6 and Fig. 12.

WRSA almost never molts its flight feathers during fall migration. The molt to winter (basic) flight feathers occurs when it reaches its wintering areas, though occasionally an early-molting basic-plumaged bird can be found on our local shores.

Newly fledged young birds arrive in New England from the Arctic later than most other juvenile shorebirds, usually in late September or October. They display the characteristic fresh, evenly patterned, scaly look of young shorebirds; see Fig. 7, Fig. 8.

Juveniles often display a minimal amount of rusty or buffy on the upper scapulars; see Fig. 7.

By mid-October, young WRSA starts shedding juvenile plumage and acquires gray winter (basic) feathers on the back (mantle); see Fig. 9.

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Breeding range, migration, wintering range, habitat

The arctic breeding areas for WRSA consist of wet meadows and low-lying areas close to marshy ponds or other wetlands, not necessarily on coasts. It feeds on small invertebrates such as mollusks and aquatic worms. It may also feed on some plant seeds.

During migration and in winter, most White-rumps are found on beaches, riverbanks, flooded fields or tidal and freshwater marshes. They feed by probing into mud or water in search of small invertebrates.

WRSA breeds along the northern coast of Alaska and a broad range of northern Canadian coastal and Arctic islands north of Hudson Bay, including Baffin Island.

WRSA arrives in arctic breeding areas at the end of May and throughout the first half of June.

Males begin leaving breeding areas by mid-June and congregate at arctic and subarctic coastal locations to fatten up for the migration flights ahead.

Females and, eventually, the young follow in late July and August.

After feeding and fattening up, some birds migrate directly over the Atlantic Ocean to the Guyanas and Suriname on the northern coast of South America.

Other birds migrate short distances to feed and fatten up along the eastern Canadian coast and the north and central Atlantic coast of the United States before heading to the northern shores of South America.

From northern South America, WRSA migrates east along the Brazil coast, then heads inland to feed along Amazonian riverbanks, and southward toward Argentina, eventually ending up as far south as Tierra del Fuego.

Northward migration of WRSA retraces the route through Argentina, Brazil, Guyanas/Suriname, then over the Caribbean or through Mexico to the US southcentral coast.

Northward migration proceeds in a broad front though the interior of North America to the Arctic coast. Cheyenne Bottoms, Kansas, is a major stopover for the species in spring.

White-rumps are scarce spring migrants in New England.

Similar species

WRSA compared to SESA

In the fall in New England, White-rumped Sandpipers (WRSA) often appear in flocks of Semipalmated Sandpipers (SESA). WRSA is noticeably larger than SESA and looks longer due to its long wings. WRSA’s white rump is usually invisible when the bird is feeding or resting. You can often see the white rump when WRSA is in flight.

Note the following. For comparison images, see Fig. 11, Fig. 12.

WRSA wings are attenuated and usually project beyond the tail when the bird is on the ground.
Male SESA bill is short and stubby. WRSA in general has a longer, slightly curved and more tapered bill; see Fig. 4.
Many White-rumps (not all) have a pale brown or reddish base to the lower mandible; see Fig. 7, Fig. 9.
The streaked and uniformly gray head, nape, shoulders, neck, and upper breast on WRSA create the impression of a cowl and an overall grayer bird than SESA. The bold eyeline (supercilium) stands out.
In nearly all plumages, WRSA has flecking—faint gray streaks—along the flanks all the way to the undertail. Breeding plumage (alternate) SESA also displays this feature, but after the breeding season most Semipalmated Sandpipers are white on the underparts and flanks.
When it is possible to see the feet well, the lack of webbing between toes is a clear indication that the bird is not a Semipalmated Sandpiper; see Fig. 7, Fig. 8.
Most White-rumps seen in New England until late September are molting summer (alternate) plumage birds. Juvenile WRSA usually appears in October; juvenile SESA is here by August and often departs by mid-October.

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WRSA compared to WESA

White-rumped Sandpiper (WRSA) migrates primarily throughout the eastern half of North America; Western Sandpiper (WESA) breeds in northwestern Alaska. WESA individuals migrate to our coast with regularity in the fall and, therefore, may be found in mixed flocks with WRSA. Similar to the comparison with SESA, WRSA is noticeably larger than WESA and looks longer due to its long wings.

Note the following:

The streaked and uniformly gray head, nape, shoulders, neck, and upper breast on WRSA create the impression of a cowl and an overall grayer bird than WESA. WESA in winter (basic) or juvenile plumage usually has a clear neck and center of breast.
In a few cases when it is possible to see the feet, the lack of webbing between toes is a clear indication that the bird is not a Western Sandpiper; see Fig. 7, Fig. 8.

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WRSA compared to SAND

White- rumped Sandpiper (WRSA) and Sanderling (SAND) are roughly the same size, though SAND is usually rounder and chunkier.

Note the following:

In spring (alternate) plumage, WRSA is grayish on the back (mantle) with some rufous highlights on the upper scapulars; SAND has highly speckled cinnamon-rufous and black upperparts, head, and neck.
Juvenile WRSA back (mantle) is scaly gray, brown and white, with a streaked gray hood over the head, neck and upper breast. Juvenile SAND mantle is a boldly checkered black-and-white; see Fig. 13.
SAND winter (basic) mantle plumage is the palest of grays, compared to the brownish-gray of WRSA.

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WRSA compared to DUNL

Dunlin (DUNL) is larger than White-rumped Sandpiper (WRSA) and has a much longer bill.

Note the following:

WRSA is long with attenuated wings; DUNL is round-bodied and chunky; see Fig. 14.
In spring and summer (alternate) plumage, DUNL has bright rusty upperparts and a blackish belly; WRSA is grayish on the back (mantle) with some rufous highlights on the upper scapulars; the underparts are white with some streaking.
During southbound migration, few DUNL arrive at New England sites before October. WRSA begin arriving at our beaches in August; some individuals linger into October or later.

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