What is the Least Sandpiper in the Audubon?

The Least Sandpiper is the smallest shorebird in the genus Calidris found throughout North America. It is a common bird seen in coastal mudflats and wetlands across its breeding and wintering range. The Least Sandpiper is known for its small size, distinctive high-pitched call, and habit of bobbing its tail. This species is closely associated with wetlands and its migratory habits have been well-studied by ornithologists.

Appearance and Size

With an average body length of just 5.5-6.5 inches (14-16.5 cm) and weight of 0.9-1.1 oz (25-32 g), the Least Sandpiper is aptly named the smallest shorebird in its genus Calidris (Jehl et al. 2001). It is smaller and more delicately built than other sandpipers. The Least Sandpiper has yellowish legs, a black bill with a drooped tip, and black eyes. Its plumage goes through distinct seasonal changes.

In breeding plumage, Least Sandpipers have bold brown and chestnut streaking on their crown and back with a white supercilium (eyebrow stripe). Their breast is white with some faint brown streaking and their belly is white. Nonbreeding plumage is much duller overall, with gray-brown upperparts and a less distinct supercilium. The white breast has more streaking and the belly remains white (Sibley 2014).

While the female Least Sandpiper is slightly larger than the male, their plumages are identical. Juvenile birds resemble nonbreeding adults but have a buff wash on the breast. Least Sandpipers molt into breeding plumage prior to migration in spring, then back to nonbreeding in late summer (Jehl et al. 2001).

Voice and Sounds

The voice of the Least Sandpiper is high-pitched, which contrasts sharply with its small size. Its flight call is a dry and rapid repetition of “dip-dip-dip.” This is useful for identification as flocks pass overhead. When on the ground, Least Sandpipers make a hoarse croak sound. Males have a longer, more melodious flight call than females during breeding season (Jehl et al. 2001).

Behavior

Least Sandpipers are restless, energetic foragers that walk briskly along the shoreline probing for food. Their tail bobs up and down frequently. They forage in loose flocks, sometimes intermingling with other small sandpipers and plovers while feeding. They are nimble on their feet and quick to take flight if alarmed, flying off rapidly with stiff wingbeats and glides while calling (Sibley 2014).

Outside of the breeding season, Least Sandpipers are highly gregarious. They migrate in large flocks and form large roosting groups while wintering. They vigorously chase each other on the wintering grounds as part of courtship displays. They are diurnal and spend most of their time actively foraging and resting briefly between bouts of foraging (Jehl et al. 2001).

Range and Habitat

Least Sandpipers breeding habitat consists of open grassy and sedge tundra near wetlands in Canada and Alaska. They nest on the ground under vegetation. During migration they stopover at mudflats, sandy beaches, flooded fields, and shorelines of lakes and rivers across North America. Their winter range extends from the southern U.S. coastline to northern South America (Sibley 2014).

In terms of their North American population, Least Sandpipers are abundant shorebirds with an estimated 1.5 million individuals. However, like many migratory birds their numbers have declined significantly in the past 50 years based on Breeding Bird Survey data. Conservation threats include habitat loss, disturbance, and climate change (Rosenberg et al. 2019).

Diet

Least Sandpipers forage by walking along the shoreline and quickly probing into mud or sand to catch small invertebrate prey. They specialize in picking tiny surface animals such as insect larvae, marine worms, crustaceans, and mollusks from wet sediments (Jehl et al. 2001). Their feeding style contrasts with larger Calidris sandpipers that probe more deeply into mud to obtain buried prey.

Breeding

Least Sandpipers arrive on the arctic breeding grounds beginning in late May. Males establish territories and perform flight displays to court females. Their nests consist of a shallow scrape lined with leaves, lichens, and moss. Females lay 3 to 4 buff-colored eggs with dark brown spotting. The eggs are incubated for about 21 days and the precocial young leave the nest within hours. The female provides most of the parental care while the male defends the territory. The young fledge in 2 to 2.5 weeks (Jehl et al. 2001).

Pairs often raise two broods in a season before undertaking the long migration in July to wintering areas. They have a relatively short life span for shorebirds of just 2 to 3 years (Jehl et al. 2001).

Migration

Least Sandpipers are champion ultralong-distance migrants that undertake an annual roundtrip of up to 18,000 miles between breeding and wintering areas (Buehler and Piersma 2008). They fly nonstop for 2500-3600 miles at a time, resting and refueling for just a few days before moving on at each stopover site.

Their migration timing and routes have been well mapped based on extensive banding records. They follow interior routes through North America in spring. In fall, western breeding birds take coastal routes through Mexico to South America and eastern breeders go over the Atlantic Ocean to South America (Birds of the World 2020).

These long flights are fueled by stored fat and periods of hyperphagia (excessive eating) to build up reserves. Least Sandpipers make use of a wide array of habitats during migration including agricultural fields and unexpected sites like golf courses and sod farms far from coastal areas traditionally associated with shorebirds (Skagen and Knopf 1994).

Status and Conservation

According to the 2016 State of North America’s Birds report, the Least Sandpiper has declined by about 40% since 1970 based on Breeding Bird Survey trends. Partners in Flight estimates their global breeding population at 1.5 million. Approximately three-quarters of the population winters in just five countries in South America (Rosenberg et al. 2019).

Major threats to Least Sandpiper populations include habitat loss and degradation on both the breeding and wintering grounds. Agricultural expansion, draining of wetlands, and development pressure continue to reduce habitat availability. Climate change may alter arctic breeding conditions and timing of food peaks during migration. Disturbance from human recreation needs to be better managed (Andres et al. 2012).

There are no directed conservation actions for Least Sandpipers currently in place. Recent initiatives aim to better understand their migration connectivity, identify key stopover habitats, and guide shorebird habitat conservation across North and South America (Senner et al. 2015). Given ongoing declines, increased conservation action is recommended for this species.

Fun Facts

Here are a few interesting tidbits about the amazing Least Sandpiper:

• Weighing under 1 ounce, the Least Sandpiper is one of the smallest shorebirds in the world!
• They migrate huge distances each year – up to 18,000 mile round trips from Alaska to South America.
• Flocks whirl and wheel through the air during dramatic aerial displays on migration and wintering grounds.
• Least Sandpipers have one of the highest wingbeat frequencies of any bird, at up to 100 beats per second!
• Their eggs are speckled and camouflaged to avoid detection on tundra nests.
• When feeding, their tail bobs up and down constantly giving them a distinctive look.

Spotting a Least Sandpiper

Here are some tips for spotting and identifying a Least Sandpiper:

• Scan shorelines, mudflats, wetlands for small, active sandpipers.
• Note bright white underparts with some faint streaking.
• Look for small size, thinner bill, bobbing tail, and hunched posture.
• Listen for high “dit dit dit” flight call of flocks passing over.
• Watch for feeding behavior – walking briskly and constantly bobbing tail.
• Seeing yellowish legs and small size helps distinguish from other “peeps”.
• In flight, appears elongate with quicker wingbeats than other sandpipers.

With their small size, distinctive appearance, and appetizing name, Least Sandpipers are a fun and rewarding bird to identify!

Least Sandpiper versus Semipalmated Sandpiper

The Least Sandpiper is often confused with the Semipalmated Sandpiper since they frequently occur together on migration and winter in similar habitats. Here is a handy comparison guide to telling them apart:

The Least Sandpiper’s smaller size, thinner bill, yellowish legs, more projecting primary tips, and constant tail bobbing help distinguish it from the very similar Semipalmated Sandpiper.

Conservation Status

The Least Sandpiper has an extensive breeding range across northern North America and winters south to South America. Its total population is estimated at 1.5 million birds. However, it has declined significantly in the past 50 years and lost 40% of its population since 1970 according to the North American Breeding Bird Survey (Rosenberg et al. 2019).

The Least Sandpiper is thus classified as Near Threatened on the IUCN Red List of Threatened Species (BirdLife International 2018). It does not have protected legal status currently but is considered a Species of Concern by state agencies in some parts of its range. Conservation plans aim to monitor Least Sandpiper populations, identify key sites, and protect habitat across their annual cycle.

Population Trend:

Decreasing; estimated 40% cumulative decline from 1970 to 2014.

Threats:

• Habitat loss and degradation on breeding, migration, and wintering grounds
• Climate change impacts on arctic breeding
• Disturbance from human recreation
• Exposure to pesticides and pollution

Conservation Actions:

• Protect key wetland habitats through legislation and land acquisition
• Manage human access/disturbance on beaches and shorebird areas
• Maintain suitable invertebrate food resources
• Monitor population trends throughout range
• Educate public on reducing disturbances and conserving shorebirds

Flock in Flight

One of the most enjoyable ways to observe Least Sandpipers is seeing a flock wheeling about in flight. Here is a description:

The shoreline suddenly explodes to life as a flock of small sandpipers takes off, alarmed by a passing dogwalker. Fifty tiny birds rise up, calling excitedly. They coalesce into a tight flock and begin flying in a rapid, twisting path over the bay. The Least Sandpipers’ stiff wingbeats and pointed wings propel them in darting turns. Their high “dit dit dit” calls create a lively chorus. The flock coils like a rollercoaster, swooping low over the water in sharp banks, then rising up to circle higher on flexed wings. Then as one, the birds descend to land back on the mudflats, their bobbing tails soon back at work.

Conclusion

In summary, the Least Sandpiper is the smallest shorebird in its genus and one of North America’s most diminutive yet spectacular migrants. This delicate brown-and-white shorebird breeds in the high Arctic each summer before undertaking heroic long-distance migrations down the coasts and across oceans to wintering grounds in South America. Least Sandpipers probe tidelines, mudflats, and wetlands for small prey, in constant motion with tail bobbing. Despite facing threats of habitat loss across their range, Least Sandpipers still perform their amazing migrations by the millions each year. Observing Least Sandpipers in their busy feeding groups and dizzying flocks is an excellent way to appreciate the wonder of shorebirds.