Calidris

Calidris is a genus of Arctic-breeding, strongly migratory wading birds in the family Scolopacidae. These birds form huge mixed flocks on coasts and estuaries in winter. Migratory shorebirds are shown to have declined in reproductive traits because of temporal changes of their breeding seasons.^[2] They are the typical "sandpipers", small to medium-sized, long-winged and relatively short-billed.

Calidris
Red knot (Calidris canutus) in juvenile plumage, Brittany, France
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Charadriiformes
Family:	Scolopacidae
Genus:	Calidris Merrem, 1804
Type species
Tringa calidris[1] = Tringa canutus Gmelin, 1789
Synonyms
Philomachus Merrem, 1804 Ereunetes Illiger, 1811 Erolia Vieillot, 1816 Limicola Koch, 1816 Machetes Cuvier, 1817 Eurynorhynchus Nilsson, 1821 Crocethia Billberg, 1828 Canutus Brehm, 1831 Aphriza Audubon, 1839 Tryngites Cabanis, 1857 Micropalama Baird, 1858

Their bills have sensitive tips which contain numerous corpuscles of Herbst. This enables the birds to locate buried prey items, which they typically seek with restless running and probing.^[3]

Taxonomy

The genus Calidris was introduced in 1804 by the German naturalist Blasius Merrem with the red knot as the type species.^[4][5] The genus name is from Ancient Greek kalidris or skalidris, a term used by Aristotle for some grey-coloured waterside birds.^[6]

Many of the species have been treated under other generic names at various times in the past, but these treatments leave Calidris polyphyletic;^[7][8] synonyms are in brackets in the list below.

The genus contain 24 species:^[9]

• Great knot Calidris tenuirostris
• Red knot Calidris canutus
• Surfbird Calidris virgata (syn. Aphriza virgata)
• Ruff Calidris pugnax (syn. Philomachus pugnax)
• Broad-billed sandpiper Calidris falcinellus (syn. Limicola falcinellus)
• Sharp-tailed sandpiper Calidris acuminata
• Stilt sandpiper Calidris himantopus (syn. Micropalama himantopus)
• Curlew sandpiper Calidris ferruginea (syn. Erolia ferruginea)
• Temminck's stint Calidris temminckii
• Long-toed stint Calidris subminuta
• Spoon-billed sandpiper Calidris pygmaea (syn. Eurynorhynchus pygmaeus)
• Red-necked stint Calidris ruficollis
• Sanderling Calidris alba (syn. Crocethia alba)
• Dunlin Calidris alpina
• Rock sandpiper Calidris ptilocnemis
• Purple sandpiper Calidris maritima
• Baird's sandpiper Calidris bairdii
• Little stint Calidris minuta
• Least sandpiper Calidris minutilla
• White-rumped sandpiper Calidris fuscicollis
• Buff-breasted sandpiper Calidris subruficollis (syn. Tryngites subruficollis)
• Pectoral sandpiper Calidris melanotos
• Semipalmated sandpiper Calidris pusilla (syn. Ereunetes pusillus)
• Western sandpiper Calidris mauri

The following species-level cladogram is based on a molecular phylogenetic study by David Černý and Rossy Natale that was published in 2022. Some of the nodes are only weakly supported by the sequence data.^[10]

Calidris

Red knot – Calidris canutus Great knot – Calidris tenuirostris Surfbird – Calidris virgata Ruff – Calidris pugnax Sharp-tailed sandpiper – Calidris acuminata Broad-billed sandpiper – Calidris falcinellus Curlew sandpiper – Calidris ferruginea Stilt sandpiper – Calidris himantopus Spoon-billed sandpiper – Calidris pygmaea Red-necked stint – Calidris ruficollis Long-toed stint – Calidris subminuta Temminck's stint – Calidris temminckii Buff-breasted sandpiper – Calidris subruficollis Sanderling – Calidris alba Dunlin – Calidris alpina Purple sandpiper – Calidris maritima Rock sandpiper – Calidris ptilocnemis Baird's sandpiper – Calidris bairdii Little stint – Calidris minuta White-rumped sandpiper – Calidris fuscicollis Least sandpiper – Calidris minutilla Pectoral sandpiper – Calidris melanotos Western sandpiper – Calidris mauri Semipalmated sandpiper – Calidris pusilla