Pectoral Sandpiper

(Calidris melanotos) (PESA)

Photographic Identification Guide

Pectoral Sandpiper (Calidris melanotos) (PESA), the quintessential “mud-peep”, is among the longest-distance shorebird migrants. It is somewhat unusual in its breeding habits; unlike many shorebirds, particularly the smaller sandpipers, male Pectorals are larger than females and initiate courtship and copulation; they take no part in incubation or rearing of the young.

PESA breed all across northern Siberia, northern Alaska and arctic Canada west of Hudson Bay. From that vast and spread out breeding range, most birds migrate to South America, wintering as far south as Tierra del Fuego. A small number winter in the Australia-New Zealand region.

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 most 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. 17. Greater Yellowlegs and Pectoral Sandpiper. Note significant size difference. Butte, CA. 3 October 2020.
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Fig. 16. Comparison of Lesser Yellowlegs and Pectoral Sandpiper. Note warm colored Pectoral vs. gray yellowlegs. Hornsby Bend, Austin, TX. 21 April 2014.
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Fig. 15. Pectoral Sandpipers and Dunlins in flight. Note Dunlins with long bills and bright white dorsal wing stripes. Monroe, Michigan. 23 April 2021.
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Fig. 14. Comparison of Pectoral Sandpipers and Semipalmated Sandpipers. Note tall posture and warm back (mantle) tones of Pectorals. Bear Creek Wildlife Sanctuary, Saugus, MA. 29 September 2019.
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Fig. 13. Comparison of Pectoral Sandpiper and Least Sandpiper, both in spring (alternate) plumage. Vancouver, British Columbia, Canada. 17 May 2019.
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Fig. 12. Pectoral Sandpiper. Note underwing pattern in flight. Cook, IL. 11 August 2023.
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Fig. 11. Pectoral Sandpiper in flight. Note brown upper body and wings (mantle) with inconspicuous pale wing stripes. Victoria, British Columbia, Canada. 22 May 2020.
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Fig. 10. Pectoral Sandpipers. Note significant size difference between male and female. Caribou, British Columbia, Canada; 1 October 2023.
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Fig. 9. Pectoral Sandpiper juveniles. Note white scapular V-marks on back (mantle) feathers. Arlington Reservoir, Arlington, MA. 27 October 2023.
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Fig. 8. Pectoral Sandpiper. Juvenile. Arlington Reservoir, Arlington, MA. 22 October 2013.
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Fig. 7. Pectoral Sandpiper. Worn summer (alternate) molting to winter (basic) plumage. Huila, Colombia. 4 November 2023.
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Fig. 6. Pectoral Sandpiper. Adult with some breeding (alternate) feathers faded or molting. Maskinonge, Quebec, Canada. 10 August 2022.
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Fig. 5. Pectoral Sandpiper male displaying full breeding form. North Slope, AK. 16 June 2019.
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Fig. 4. Pectoral Sandpiper male performing courtship flight. North Slope, AK. 15 June 2016.
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Fig. 3. Pectoral Sandpipers. Most birds in spring (alternate) plumage. Hornsby Bend, Austin, TX; 2016.04.19.
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Fig. 2. Pectoral Sandpiper. Spring (alternate) plumage. Hornsby Bend, Austin, TX. 21 April 2014.
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Fig. 1. Pectoral Sandpiper. Winter (basic) plumage. Note plain gray-brown coloration. Punto Arenas, Chile; 3 January 2022.

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

Basic: winter plumage, roughly mid-September to mid-February.

PESA completes molting to winter (basic) plumage toward the end of the calendar year, usually when it approaches or arrives at its winter range; see Fig. 1.

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

Beginning in late February, winter (basic) feathers on PESA are gradually replaced by spring and summer (alternate) feathers; see Fig. 2.

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

See Fig. 8, Fig. 9. 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

Body length:

7.5-9 in. (19-23 cm)

Wingspan:

14.6-17.7 in. (37-45 cm)

Bill length:

1–1.25 in. (25.1-31.7 mm)

Male weight:
Female weight:

1.6-4.4 oz. (45-126 g)
1.1-3.4 oz. (31-97 g)

Calls

PESA often utters a raspy creeck when it first takes off.

Calls in Puerto Hamburgo, Bolivia, 2013:

Calls in Barrow, AK, 2017:

Courtship songs and displays, only seen on the breeding grounds, are diverse and, sometimes, spectacular. For example, see a courtship display in North Slope, Alaska, 2019:

Plumage and other characteristics

At all seasons, PESA displays a heavily marked breast with the streaks terminating abruptly at the belly. The plumage is generally warm-colored or buffy, the bill is medium long, slightly downcurved and often bicolored, and the legs are yellowish, pale yellow-green or pale orange; see Fig. 2.

Breast-to-belly demarcation line is V-shaped, particularly noticeable in spring and summer (alternate) plumaged birds; see Fig. 6.

PESA in winter (basic) plumage has grayish brown back (mantle) feathers which are pale on the margins and have large dark gray centers; see Fig. 1.

Beginning in late February, winter (basic) plumage is slowly replaced by spring (alternate) feathers with broad blackish-brown centers and wide gray margins. The crown, upper scapulars and tertial feathers have variable chestnut or buffy margins. See Fig. 2, Fig. 3.

Pectoral Sandpiper males are considerably larger and heavier than females; see Fig. 10. This size difference is usually noticeable when the birds are seen in migration and becomes exaggerated on the breeding grounds because the male puts on extra weight. Loose neck skin and inflatable breast pouches during courtship gives the male extra heft; see Fig. 4, Fig. 5.

Spring (alternate) and summer (alternate) are the same plumage; however, as seasons advance, colors fade or feather margins become worn and the plumage looks different. In Fig. 6, note how the worn and faded alternate back (mantle) feathers and fresh winter (basic) feathers combine to produce a muted salt-and-pepper appearance.

Old summer (alternate) feathers become frayed but can last into fall of the same year; see Fig. 7.

Newly fledged young birds usually arrive in New England from the Arctic starting in late July, though most individuals are encountered in October. They display the characteristic fresh, evenly patterned, scaly look of young shorebirds; see Fig. 8.

White tips to the scapular feathers produce two parallel V-marks on the back (mantle) of the juvenile; see Fig. 8, Fig. 9.

In flight, PESA is mostly brown on the back (mantle). The tail is brown with small white patches on the sides. The wings are mostly brown above but sometimes show a very narrow pale stripe; see Fig. 11, Fig. 15.

From below, PESA in flight has a white belly and streaked breast and throat. The undersides of wing leading edges are streaked with dark gray; see Fig. 12.

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Breeding range, migration, wintering range, habitat

Breeding range of PESA extends from central Canadian Arctic north and west of Hudson Bay to northern and western Alaska and more than 3,000 miles (5,000 km) west along the Siberian Arctic coast.

Breeding birds arrive in Arctic regions in late May and early June. Females pick nesting sites, mate with males and are thereafter solely responsible for incubation of eggs and care of young.

Males leave nesting areas in mid-summer, well before females and the young.

In late summer and fall, most Siberian breeders head east to the North American Arctic before heading south, but some head south or southeast to Australasian wintering areas.

In late summer and fall, adults in Arctic North America move in a broad front through the Great Plains and across Central America and the Gulf of Mexico to South America. Juveniles disperse across North America somewhat more, fattening up on either east or west coast before heading to South America.

The western hemisphere wintering range is primarily central and southern South America as far south as Tierra del Fuego. In the eastern hemisphere, small numbers winter in Polynesia, southeastern Australia and New Zealand.

Northward migration of PESA retraces the route through South and Central America and the Gulf of Mexico to the Mississippi Flyway in North America. Most birds migrate across a broad front west of the Mississippi Valley and east of the Rocky Mountains until they reach Arctic Canada and disperse to breed.

Due to the extent of its breeding range in Siberia and the distance that most Pectoral Sandpipers traverse in returning to the (presumed) ancestral wintering areas in South America, this species is considered among the longest distance migrants of all; birds at the extremes of their range appear to travel 18,000 miles (30,000 km) in a year.

Arctic breeding zones for PESA consist of bogs or tundra close to wet, highly vegetated areas. It nests on low ridges or slightly elevated mounds on the coastal plain.

In nesting areas, the primary food is larvae of insects such as crane flies and midges.

Migration and wintering habitats are grasslands, marshes and wetlands, rarely coastal tidal sites. PESA earns the nickname “mud-peep” because it is often found belly- and bill-deep in muddy habitats.

During migration and on the wintering grounds, larvae and adults of many terrestrial and aquatic arthropods (insects), gastropods (snails), crustaceans (crabs) and even small minnows are consumed, as well as occasional plant seeds.

Similar species

PESA compared to LESA

Pectoral Sandpiper (PESA) and Least Sandpiper (LESA), though quite dissimilar in size (Pectoral is much larger), resemble each other sufficiently so that if one is seen without a size scale nearby (such as a bird of another species for comparison), it is possible to mistake one for the other; see Fig. 13.

Note the following:

PESA breast streaking is bold throughout the year and terminates abruptly at the belly. LESA breast markings are boldest in spring (alternate) plumage and fade in time. The center of LESA breast in winter (basic) plumage can be nearly unmarked.
PESA bill is often bi-colored with pale base. LESA bill is all black and tapered with a very fine point.
PESA often stands tall, whereas LESA posture is often hunched.

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PESA compared to SESA

Pectoral Sandpiper (PESA) is much larger than Semipalmated Sandpiper (SESA) and looks much browner in most plumages; see Fig. 14.

Note the following:

SESA bill is short, usually straight and black. PESA bill is longer, slightly curved and often pale at the base; the latter feature is most noticeable in juvenile birds.
PESA breast is distinctly streaked and gives a bib-like effect, ending abruptly at the belly. SESA breast streaking is diffuse and faint, often fading toward the center of the breast.
PESA legs are pale green, yellow or orange. SESA legs are dark gray, dark green or black.

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PESA compared to DUNL

Pectoral Sandpiper (PESA) is slightly larger and often stands taller than Dunlin (DUNL), which frequently stands in a hunched posture.

Note the following:

PESA in spring (alternate or breeding) plumage is rufous and brown on the back, neatly streaked on the breast and white-bellied. DUNL in breeding plumage is rufous and black on the back and has a large black patch on the belly.
In the fall, when both species are most likely to be seen in the New England region, DUNL arrives late (October usually) and is often mostly molted into gray winter (basic) plumage. Most Pectorals we see at that season are brightly plumaged juveniles with rufous and buffy tones.
PESA seldom are seen along the shore; DUNL are often along the ocean shore.
DUNL has a long black bill which is noticeably down curved. The often bicolored PESA bill is shorter and straighter; see Fig. 15.
In flight, PESA appears evenly brown-backed with a barely noticeable pale wing-stripe. The DUNL wing-stripe is bold and bright; see Fig. 15.

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PESA compared to BASA

Pectoral Sandpiper (PESA) is larger than Baird’s Sandpiper (BASA). Both are warm-colored in most plumages and display a bib-like streaked breast.

Note the following:

BASA bill is black and straight. PESA bill is longer, slightly curved and often pale at the base.
PESA legs are yellow, greenish or orange. BASA legs are black.
BASA bib of streaks ends abruptly at the belly in a straight line. PESA bib terminates in a distinct V, particularly noticeable in a spring or summer (alternate) plumaged bird; see Fig. 6.

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PESA compared to yellowlegs

Pectoral Sandpiper (PESA) is nearly always in a warmer, browner plumage than either of the yellowlegs species. For comparison images, see Fig. 16, Fig. 17.

Note the following:

Yellowlegs have bright yellow or yellow-orange legs. PESA legs are often a clouded orange or yellow, sometimes with greenish mixed in.
PESA usually displays a bold pale eyebrow and darker cap. Yellowlegs display an eye-ring and no strongly contrasting cap.
Yellowlegs are checkered black-grey-white or spotted, whereas PESA is streaked brown.
Lesser yellowlegs (LEYE) and PESA are close in size. If seen standing side by side with PESA, LEYE is slightly larger and considerably taller, due to its much longer legs.
LEYE bill is tapered and all black with a fine point. PESA bill is often thick and paler at the base.
Greater Yellowlegs (GRYE) is much larger than PESA and stands much taller.
GRYE has a much longer bill than PESA. The pale base of the GRYE bill is grayish, whereas the pale base of the PESA bill is usually brown or smudged orange.

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