Calidris acuminata (Horsfield, 1821)

Common Name and Body Shape

Calidris acuminata, commonly called the sharp-tailed sandpiper, is a small-to-medium portly wader with a pot belly, flat back, and a somewhat elongated rear end.

Upper Body and Head Plumage

Its upper body is mottled chestnut-brown, with distinct feathers that each have a dark centre; it also has a chestnut cap on its head and a brown stripe running through each eye.

Bill and Leg Coloration

The bill is straight, and ranges from dark grey to black, while the legs are olive to yellow.

Underpart Plumage

The underparts are white or pale, with mottling matching the pattern on the breast and sides of the belly.

Seasonal Plumage Variation

Plumage is more vivid during breeding season, and duller in winter.

Juvenile Plumage

Juveniles are brighter in autumn and early winter than adults, with sharper feathers and brighter chestnut crowns that contrast with white mantle stripes and bright buffy chests.

Similarity to Pectoral Sandpiper

The sharp-tailed sandpiper is most similar in appearance to the pectoral sandpiper, and breeds within the Asian range of the pectoral sandpiper.

Breast Pattern Differences from Pectoral Sandpiper

It differs from pectoral sandpiper in its breast pattern: it lacks a strongly demarcated breast band, and instead has '>'-shaped marks on the flanks.

Head Feature Differences from Pectoral Sandpiper

It also has a stronger supercilium and a more chestnut-coloured crown.

Comparison to Long-toed Stint

It shares some similarities with the long-toed stint, but is much larger.

Breeding Range

The sharp-tailed sandpiper is strongly migratory, and breeds only in eastern Siberia, from the Taymyr Peninsula to Chaunskaya Bay in Chukotka.

Migration Timing and Wintering Range

It has a complex migration: adults depart Siberia in July, and juveniles depart in August to head south, with the majority of the population wintering in Australasia.

Migration Route Count

The species takes two main migration routes.

First Migration Route Initial Path

Most post-breeding adults fly south in flocks of fewer than 1000, travelling east of Lake Baikal to the Pacific coast of Russia and the Yellow Sea coasts of China, Korea, and Japan.

First Migration Route Southern Stops

Most of these birds fly directly to Micronesia and New Guinea in late August, then depart when the wet season begins to travel to northwest Australia in mid-September.

First Migration Route Australian Movement

They then begin moving toward southeast Australia, with numbers peaking there between December and February.

Second Migration Route Initial Path

The second route heads east, and is used by most juveniles and a small number of adults, which cross the Bering Strait into Alaska.

Trans-Pacific Flight Details

They stay in Alaska from mid-August to late October to build up fat reserves, and are presumed to then make a direct non-stop trans-Pacific flight of more than 10,000 km to reach Australia and New Zealand.

North America Vagrancy Records

Some individuals continue south along the Pacific coast of North America into Washington, and less frequently reach California, and may occasionally reach Latin America; only two recent records exist from Panama and Bolivia.

Europe and North America Migrant Status

The sharp-tailed sandpiper occurs as a rare autumn migrant to North America, and is a very rare migrant in western Europe, with records from 11 different countries (mostly the United Kingdom) between August and October.

Middle East and Central Asia Records

It has also been recorded in the Middle East and Central Asia, with six records in Kazakhstan, and one each in Yemen and Oman.

Christmas Island Records

In the Indian Ocean, it has been documented four times (totalling 16 individual birds) at Christmas Island between October and December.

Other Indian Ocean Records

There have been three recorded observations at Cocos Island in November and December, five records at the Chagos archipelago from September to December, and five records in Seychelles: one in July, two overwintering from September to February, and two on passage in November.

Southern Africa Record

It was recently documented in Mozambique, when it was recorded in southern Africa for the first time in 2018.

Siberian Breeding Habitat

In Siberia, its breeding habitat is mostly peat-hummock and lichen tundra.

Migration Stopover Habitat

During migration passage between breeding and wintering areas, it favours the muddy edges of shallow freshwater or brackish wetlands with grass, emergent or inundated sedges, saltmarsh or other low vegetation.

Migration Wetland Types

These habitats include swamps, lakes, lagoons, and pools near coasts, as well as inland waterholes, dams, saltpans, and hypersaline salt lakes.

Alaska Habitat Preference

In Alaska, the species appears to prefer coastal moist graminoid meadows and riverine intertidally exposed mudbanks.

Australian Primary Habitat

In Australia, it is largely found around wetlands, and prefers inland freshwater wetlands with grassy edges.

Australian Coastal Habitat Use

After ephemeral terrestrial wetlands dry out, it tends to be seen on coastal mudflats, salt marsh, and brackish lagoons, and less often in similar wet short-grass fields.

Australian Secondary Habitat Locations

Other locations it has been spotted in Australia include around sewage farms, flooded fields, mangroves, rocky shores, and beaches.