The Curlew Sandpiper is a small, slim sandpiper 18–23 cm long and weighing 57 g, with a wingspan of 38–41 cm. The legs and neck are long. The bill is also long, and is decurved with a slender tip. The bill is black, sometimes with a brown or green tinge at the base. The head is small and round, and the iris is dark brown. The legs and feet are black or black-grey. When at rest, the wing-tips project beyond the tip of the tail. The sexes are similar, but females have a slightly larger and longer bill and a slightly paler underbelly in breeding plumage.
In breeding plumage, the head, neck and underbody to rear belly are a rich chestnut-red with narrow black bars on the belly and flanks. There are black streaks on the crown, a dusky loral stripe, and white around the base of the bill. The head, neck and underbody have a pale-streaked appearance due to white tips on the feathers. The feathers on the mantle and scapulars are black with large chestnut spots and grayish-white tips. The back and upper rump are dark brown, with a prominent square white patch across the lower rump and uppertail-covert.
The non-breeding plumage is similar to the breeding plumage. Differences are that the cap, ear-coverts, hindneck and sides of neck are pale brownish-grey with fine dark streaks, grading to off-white on the lower face, with white on the chin and throat. There is a narrow dark loral stripe and white supercilium from the bill to above the rear ear-coverts. The mantle, back, scapulars, tertials and innerwing-covert are pale brownish-grey with fine dark streaks. The underbody is white with a brownish-grey wash and fine dark streaks on the foreneck and breast.
The Curlew Sandpiper, although breeding in northern Asia, seems to stray to many parts of the world outside of its normal haunts
The numbers of this species (and of Little Stint) depend on the population of lemmings. In poor lemming years, predatory species such as skuas and Snowy Owls will take Arctic-breeding waders instead.
This species occasionally hybridizes with the Sharp-tailed Sandpiper and the Pectoral Sandpiper, producing the presumed "species" called "Cooper's Sandpiper" and "Cox's Sandpiper.”
A group of sandpipers has many collective nouns, including a "bind", "contradiction", "fling", "hill", and "time-step" of sandpipers.
The Curlew sandpiper is a very long distance migrant, although much of the migration and staging strategy is not fully understood.
The Curlew Sandpiper gives a soft, rippling “kirrip” or “prrriit”. The song is more complex, including series of chatters, trills and whinnies.
The Curlew Sandpiper feeds on crustaceans (amphipods and shrimps), molluscs, marine worms and insects (mainly flies and beetles). Insects are the main part of the diet during the breeding season. Some seeds can be eaten too.
It feeds in shallow water and wet mud, pecking prey from the surface or probing in mud with the bill. It feeds both by day and by night.
Outside the breeding season, it is gregarious and forms large, mixed-species flocks on feeding areas and at roosting sites.
At the beginning of the breeding season, the Curlew Sandpiper establishes the territory by calling, often perched on mound or some elevated place. The male performs a low flight display with slow wingbeats interspersed with glides and accompanied by song.
Other displays show the male pursuing the female in flight. On the ground, the male circles the female, running in zigzag pattern with raised wings and fanned tail, in order to expose the white rump. Both mates also perform ritualized nest-making movements. The male does not take part in nesting duties.
The Curlew Sandpiper is migratory. The males leave the breeding grounds in late June/early July, about 3-4 weeks before the females. They reach Africa from mid-July in north, and mostly September in south. It reaches Australia in late August/early September. The juveniles migrate 4-6 weeks later than adults.
The return migration occurs in late April to May. The breeding grounds are reoccupied from early June. The 1st year birds often remain on the breeding areas.
The Curlew Sandpiper has swift, direct flight with rapid wingbeats.
The diet of the curlew sandpiper mainly consists of insects and other small invertebrates such as crustaceans, mollusks and worms, but it will also occasionally feed on seeds and other plant material. It uses its magnificent bill to forage in the mud for prey, and probes continuously as it walks quickly across its habitat.
The breeding season takes place in June-July. The Curlew Sandpiper nests on the tundra close to marshes and pools, or along low ridges and gentle slopes in the wet, grassy tundra.
The nest is on the ground, with a density ranging from 2-3 nests/km², sometimes 200-300 metres apart, or up to 50 birds/km².
The nest is a shallow scrape on the ground, lined with leaves, moss and lichens. It is built by the female alone. Sometimes, several females may nest close together, involving probably better nest defence.
The female lays 3-8, usually 4 cryptic creamy-white to olive eggs with dark markings. She incubates alone during 19-21 days. The chicks leave the nest soon after hatching, and the female leads them to more grassy areas in the tundra. They are able to feed themselves, but they are accompanied by the female. They fledge two weeks after hatching.
This species is a rare visitor to Maldives.
In Maldives, this species is protected by law since 22nd May 2003.
The Curlew Sandpiper is currently classified as ‘Near Threatened’ by IUCN.
All waders are affected by coastal development, including drainage and land-clearing in their preferred habitats.