Least Sandpiper

(Calidris minutilla) (LESA)

Photographic Identification Guide

Least Sandpiper (Calidris minutilla) (LESA) is one of five species of small sandpipers referred to as “peeps” in North America. The smallest species of sandpiper in the world, LESA is best distinguished from its closest Nearctic look-alikes by the color of its legs: yellow-green or green-yellow or pale mud, sometimes orangish, depending on the light. In nearly all photographs, the color of the legs is visible, but that is not always the case in the field.

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. Least Sandpiper. Winter (basic) plumage found in southern U.S., Mexico, Caribbean, and northern South America. Hornsby Bend, Austin, TX. 19 February 2022.
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Fig. 2. Least Sandpipers. Winter (basic) plumage in afternoon light, pale legs, hunched posture. Estero Llano Grande, Weslaco, TX. 27 January 2018.
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Fig. 3. Least Sandpipers. Winter (basic) plumage. Note fine-tipped bill, breast band faded toward center of breast. Hornsby Bend, Austin, TX. 22 January 2022.
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Fig. 4. Least Sandpiper molting from winter (basic) to spring (alternate) plumage. Hornsby Bend, Austin, TX. 12 March 2023.
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Fig. 5. Least Sandpiper. Fresh spring (alternate) plumage, fine-tipped down-decurved bill, pale legs, streaked bib across entire breast. Hornsby Bend, Austin TX. 17 April 2017.
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Fig. 6. Least Sandpiper. Fresh spring (alternate) plumage, chestnut and pale margins on mantle feathers, streaked bib across entire breast. McFaddin NWR, TX. 8 May 2015.
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Fig. 7. Least Sandpipers. Worn summer (alternate) plumage, dark mantle feathers with worn margins, heavy dark bib visible at distance. Rumney Marsh, Revere, MA. 1 August 2021.
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Fig. 8. Least Sandpipers. Worn summer (alternate) plumage. Female’s bill is longer; male’s bill is shorter. Belle Isle Marsh, East Boston, MA. 8 July 2014.
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Fig. 9. Least Sandpiper. Worn summer (alternate) plumage, and bird is beginning molt to winter (basic) plumage. Rumney Marsh, Revere, MA. 17 July 2019.
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Fig. 10. Least Sandpiper. Summer (alternate) plumage feathers have broad dark centers and narrow worn edges; fresh winter (basic) feathers have narrow dark centers and broad pale margins. Rumney Marsh, Revere, MA. 17 July 2019.
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Fig. 11. Least Sandpiper. Note Salt-and-pepper effect of worn summer (alternate) plumage as bird begins to molt to fresh winter (basic) plumage. Ninigret Flats NWR, Charlestown, RI. 26 August 2018.
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Fig. 12. Least Sandpiper. Juvenile plumage, with conspicuous V-marks on mantle, lower scapulars with white margins. Nahant Beach, Nahant, MA. 2 September 2016.
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Fig. 13. Least Sandpiper. Juvenile plumage, with conspicuous V-marks on mantle; white-edged lower scapulars form dotted line. Winthrop Beach, Winthrop, MA. 24 August 2015.
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Fig. 14. Least Sandpiper. Juvenile plumage, with conspicuous V-marks on mantle and lower scapulars. Ninigret Flats, Charlestown, RI. 22 August 2018.
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Fig. 15. Least Sandpiper. Juvenile plumage, with inconspicuous dorsal V-marks and, short primary projection. Winthrop Beach, Winthrop, MA. 3 September 2014.
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Fig. 16. Comparison of Semipalmated Sandpiper (SESA) and Least Sandpiper (LESA), both in juvenile plumage. Winthrop Beach, Winthrop, MA. 6 September 2021.
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Fig. 17. Least Sandpiper showing short P10 primary feathers, dusky underside of wingtips. Hornsby Bend, Austin, TX. 12 March 2023.

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

Basic: winter plumage, roughly late November to March.

LESA acquires winter (basic) plumage toward the end of the calendar year, usually when it approaches or arrives at its winter range; see Fig. 1. Birds that are fully molted into this plumage are rarely seen in New England.

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

Beginning in spring, winter (basic) feathers on LESA are gradually replaced by spring and summer (alternate) feathers; see Fig. 4, Fig. 5. Most alternate feathers last until fall of the same year; replacement by winter (basic) feathers begins in July or August; see Fig. 10, Fig. 11.

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

See Fig. 12. These feathers are acquired on the breeding grounds immediately after the natal down is shed and before the young begin their migration.

Size and weight

Body length:

4.5–4.75 in. (11.4–12 cm)

Wingspan:

13.25–14 in. (33.6–35.6 cm)

Bill length:

0.67–0.74 in. (17–18.8 mm)

Weight:

0.3–1 oz. (8.5–28 g)

Calls

LESA often feeds and roosts in dense grass or in small puddles in a marsh. The birds may flush before you see them, so you hear them as they fly away. The high-pitched calls in flight, often transcribed as jeer-jeer, kreep-kreep or breep-breep, are unlike those of any other small shorebird. Sibley’s phone app has a good selection of LESA call recordings.

Calls in NH, 2021:

Calls in Montauk, NY:

Plumage and other characteristics

The legs are pale, ranging from yellow-green to green-yellow to orangish; see Fig. 1.

Lighting, such as warm afternoon sunlight, can change perception of leg color; see Fig. 2.

If the bird is lit directly from above in noonday sun, its legs may look dark. The legs may be covered with dark mud.

The bill is tapered, slightly down-curved and fine-tipped; see Fig. 1, Fig. 5. On distant birds, a scope may be necessary to see the bill shape clearly; see Fig. 7.

Female LESA bills are surprisingly long. In Fig. 8, note the difference in bill lengths between the two birds. The bird in the foreground is presumed to be female; the bird in the background, male.

In most LESA and in most plumages, there is a complete dark bib across the upper breast. The complete bib is fairly reliable as a way to separate LESA from Semipalmated Sandpiper (SESA) in New England during fall migration; see Fig. 7, Fig. 9.

Few LESA attain full winter (basic) plumage when passing through New England. Eastern birds do not complete full molt to winter (basic) plumage until they reach their wintering grounds in southeastern and south-central U.S. or south of the U.S. border. West Coast birds complete full molt to winter (basic) plumage by the time they reach California in late summer or early fall.

Winter (basic) birds are dull grayish brown; see Fig. 1, Fig. 3. Angle of lighting can make them appear almost golden; see Fig. 2, which was taken in afternoon light in Texas.

In winter (basic) plumage, the dark bib feathers at the center of the breast may be faded; see Fig. 1, Fig. 3.

Beginning in March, winter (basic) plumage is slowly replaced by spring (alternate) plumage; see Fig. 4.

Alternate plumage on birds reaching their first year of life (fledged the previous summer) is less colorful than alternate plumage on breeding-age birds two years old or older.

Alternate plumage on two-year-old or older birds, when fresh in April and May, is rich with blackish centers and broad pale and chestnut margins on the mantle feathers; see Fig. 5, Fig. 6.

In alternate plumage, breast markings are sharp, sometimes arrowhead-shaped, on a mostly pale or very pale buffy background; see Fig. 6. Depending on the light and your angle of view, the entire breast can look dark; see Fig. 7, Fig. 14.

Most LESA seen in New England are darker, richer-colored and redder than the other small Calidris sandpipers.

Spring (alternate) and summer (alternate) plumages consist of the same feathers, though more worn on the edges in the summer, therefore looking somewhat different, as described below.

In the summer, alternate feathers lose much of their pale and rufous edging. On adult birds returning from the Arctic in July and August, worn back (mantle) feathers look dark, almost black. High summer sun emphasizes this feature; see Fig. 7, Fig. 8, Fig. 9.

When molting to winter (basic) plumage, alternate-plumaged birds display a salt-and-pepper appearance as the worn, dark older feathers are replaced with new paler feathers with dark central shafts; see Fig. 10, Fig. 11.

The beautiful juvenile birds arrive in August after fledging in northern and low arctic areas of Canada and Alaska. They have the characteristic fresh, evenly patterned look of all young shorebirds. Every feather is the same age, so they have a uniform repeated pattern that seems to clothe the bird in a scaly cloak; see Fig. 12, Fig. 13, Fig. 14, Fig. 15.

In many juvenile LESA, pale mantle and lower scapular feather margins create two parallel Vs on the dorsal surface of the bird. These are easily visible in Fig. 12, Fig. 13, Fig. 14, not as conspicuous in Fig. 15.

Back (mantle) V-marks are more easily seen in juveniles than other age classes, but see adult birds in Fig. 8.

LESA hunches over, pulls its neck in, and often walks in a slight crouch with ankles (“knees”) bent; see Fig. 15.

In flight, LESA outer primaries, particularly P10, are short, giving the bird a round-winged appearance. Also in flight, wingtips are slightly dusky when viewed from below; see Fig. 17.

The primary tips, when folded (at rest) fall slightly short of the tip of the tail; see Fig. 15.

During short flights (between marsh puddles, for example), LESA wing beats are shallow and stiff, somewhat reminiscent of Spotted Sandpiper (SPSA).

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Breeding range, migration, wintering range, habitat

LESA nests in northern Canada and in Alaska.

LESA winters in the southern U.S., Mexico, Central America, and northern South America.

LESA spring migration starts earlier than for most small shorebirds. Marshes in Massachusetts resound with the jeer-jeer of LESA by the second week of April. A few northbound migrants remain in New England locations until the third week of May.

Post-breeding LESA adults begin returning to New England marshes in early July and are most common in August. By September they are relatively scarce in coastal and marsh locations.

Feeding and roosting LESA congregate in small groups in the grass of marshes, but can be found on mudflats with other shorebirds as well.

During migration as well as on the wintering grounds and on breeding grounds, LESA food consists of very small invertebrates including insect larvae. In the fall some plant material such as seeds are also consumed.

Similar species

LESA compared to SESA

Least and Semipalmated Sandpipers (LESA, SESA) are close in size and shape. In all plumages and ages, note the following:

Overall color: warmer, redder tones for LESA; colder, grayer tones for SESA. Juveniles are most distinctive; see Fig. 16.
Leg color: pale yellow or yellow green for LESA; dark gray or dark green for SESA.
Toes are separated in LESA; toes are partially webbed in SESA. This is hard to see in the field.
Bill often looks slimmer, longer and somewhat downturned in LESA compared to SESA.
Posture: LESA posture is hunched; SESA posture is more upright.

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LESA compared to WESA

Least and Western Sandpiper (LESA, WESA) are close in size and shape. Note the following:

WESA coloration in all plumages is grayer than LESA.
WESA spring or summer (alternate) plumage is rufous on scapulars, crown, and cheeks, contrasting strongly with grayer overall plumage.
Leg color: pale yellow or yellow green for LESA; dark grey or dark green for WESA.
Toes are separated in LESA; toes are partially webbed in WESA. This is hard to see in the field.
Bill is longer and more downturned in WESA compared to LESA; this is more easily picked out in females than males.