User:MSK/Curlew sandpiper

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Curlew sandpiper
File:Calidris ferruginea - non-breeding.jpg
Non-breeding adult in grey-and-white winter plumage
Conservation status
Vulnerable (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Charadriiformes
Family:	Scolopacidae
Genus:	Calidris
Species:	C. ferruginea
Binomial name
Calidris ferruginea (Pontoppidan, 1763)
Synonyms
Tringa ferrugineus Pontoppidan, 1763 Scolopax testacea Pallas, 1764 Scolopax subarquata Güldenstädt, 1775 Erolia variegata Vieillot, 1816

The curlew sandpiper (Calidris ferruginea) is a small wader of the family Scolopacidae that breeds on the tundra of Arctic Siberia. It is a long-distance migrant, wintering mainly in sub-Saharan Africa, with additional populations in South Asia, Southeast Asia, Australia, and New Zealand. Named for its distinctive downward-curving bill—reminiscent of a curlew—it undergoes a striking seasonal transformation: in breeding plumage the head, breast, and underparts are a rich brick-red, while in the non-breeding season the bird is a subdued grey above and white below.

The curlew sandpiper is highly gregarious, often forming large flocks at tidal mudflats and saltpans during migration and on its wintering grounds. It forages by probing and pecking through soft mud for invertebrates, including worms, molluscs, crustaceans, and insects. The species has no recognised subspecies and is monotypic.

As of 2024, the IUCN Red List classifies the curlew sandpiper as Vulnerable, having been uplisted from Near Threatened following evidence of a population decline of 30–49% over the preceding three generations, driven primarily by habitat loss along the East Asian–Australasian Flyway and the effects of climate change on breeding productivity.

Taxonomy

The curlew sandpiper was formally described in 1763 by the Danish naturalist Erik Pontoppidan in his Danske Atlas, where he gave it the binomial name Tringa ferrugineus. The specific epithet was later feminised to ferruginea in accordance with the gender of the genus Calidris, as corrected by Morten Thrane Brünnich in 1764. The genus name Calidris derives from the Ancient Greek kalidris or skalidris, a term used by Aristotle for grey-coloured waterside birds. The specific epithet ferruginea is from the Latin ferrugo, "iron rust", a reference to the bird's colour in breeding plumage.

The species has no recognised subspecies and is considered monotypic. Within the genus Calidris, the curlew sandpiper is most closely related to the stilt sandpiper (Calidris himantopus); together they form part of a small clade that also includes the spoon-billed sandpiper, Temminck's stint, red-necked stint, and long-toed stint.

The curlew sandpiper is the probable parent of two hybrid forms once described as distinct species. Cooper's sandpiper (Calidris × cooperi) is a hybrid with the sharp-tailed sandpiper, while Cox's sandpiper (Calidris × paramelanotos) results from a cross between a male pectoral sandpiper and a female curlew sandpiper, first found in Australia in the 1950s.

Description

The curlew sandpiper is a small to medium-sized shorebird, measuring 18–23 cm (7–9 in) in length with a wingspan of 38–41 cm (15–16 in) and a body mass of 44–117 g (1.6–4.1 oz). It is slightly larger than the closely related dunlin (Calidris alpina) and can be distinguished from it by its longer, more slender, and more evenly downcurved bill, longer legs, and longer wings, giving the bird an overall elongated appearance. In flight, a broad white rump patch is a highly distinctive feature across all plumages.

Plumage

The species has three main plumage types that vary with age and season.

In breeding plumage, the adult is unmistakable: the face, neck, breast, and belly are a deep brick-red to chestnut colour, more intensely saturated in males. The upperparts are dark grey and brown, patterned with rufous and white fringes, producing a spangled appearance. Fresh breeding plumage may show subtle pale scalloping on the underparts from white feather tips that wear away over the season.

In non-breeding (winter) plumage, the bird is considerably plainer: the upperparts are pale grey and the underparts are white, with a prominent white supercilium bordered above by a grey cap. There is some light grey streaking across the breast. In this plumage the curlew sandpiper superficially resembles the dunlin, though it retains its distinguishing features of longer bill, longer legs, and white rump.

Juvenile plumage resembles the non-breeding adult but with a warm buff or creamy wash across the breast and pale fringes on the scapulars and wing coverts, giving a neatly scaly appearance. First-year birds do not migrate to the breeding grounds and remain on the wintering range year-round; they may nonetheless partially moult into a breeding-type plumage with white spotting on the chest.

The bill is black and long, with a smooth, even downcurve along its entire length. The legs and feet are black. Adult males and females are similar in plumage but males tend to show deeper, more uniform red colouring during the breeding season.

Distribution and habitat

Breeding range

The curlew sandpiper breeds exclusively on the tundra of the high Arctic, with a range extending from the Yamal Peninsula in western Siberia eastward to Kolyuchin Bay on the Chukotka Peninsula, spanning roughly from 72°E to 174°W. The species is absent from the westernmost and easternmost extremes of the Siberian Arctic, giving it one of the smallest breeding ranges relative to its non-breeding range of any shorebird in the world.

Breeding habitat consists of lowland tundra with an abundance of shallow boggy depressions, pools from melting permafrost, and hummocky grassland; the species avoids barren ground and areas with tall or dense vegetation.

Wintering range and migration

Following the breeding season, curlew sandpipers undertake one of the longest migrations of any shorebird, with wintering grounds predominantly in sub-Saharan and southern Africa, but also across the coasts of South Asia, Southeast Asia, Australia, and New Zealand—a journey of up to 15,000 km from their Siberian breeding grounds. South Africa represents the southernmost point of the migration from Siberia, spanning approximately 130° of latitude.

During migration and in the non-breeding season, the species favours tidal mudflats, saltpans, sandy beaches, shallow lake edges, rice paddies, and sewage lagoons. It is highly gregarious at these sites and regularly forms mixed-species flocks with dunlin and other Calidris waders.

Despite having an entirely easterly breeding range in Siberia, the curlew sandpiper is a regular passage migrant in Western Europe, including the British Isles, presumably owing to a broad southwesterly migration trajectory in autumn. It is a scarce but annual vagrant on the Atlantic coast of North America, most typically in juvenile or breeding plumage.

Behaviour

Feeding

The curlew sandpiper is omnivorous and opportunistic. On the breeding grounds, it feeds principally on insects and their larvae, especially flies and beetles. On the non-breeding grounds, the diet broadens considerably to include polychaete worms, molluscs, crustaceans (including amphipods and shrimp), and occasionally seeds of marsh plants such as Salicornia.

The species forages on soft mud and in shallow water, using a combination of visual pecking and tactile probing—jabbing its bill repeatedly into the substrate in a characteristic "stitching" motion. It will wade into water up to belly depth while probing.

Breeding

Curlew sandpipers arrive on the Siberian breeding grounds in June, with breedCategory:Migratory birds (Eastern Hemisphere)