Dunlin

Calidris alpina (Linnaeus, 1758)

Order: Charadriiformes

Family: Scolopacidae

New Zealand status: Native

Conservation status: Vagrant

Other names: red-backed sandpiper, black-bellied sandpiper, blackcrop

Geographical variation: Up to eleven subspecies have been described; the subspecific identity of the birds recorded in New Zealand is unknown.

Dunlin. Overwintering bird moulting into breeding plumage. Manukau Harbour, April 2006. Image © Phil Battley by Phil Battley

Dunlin. Overwintering bird moulting into breeding plumage. Manukau Harbour, April 2006. Image © Phil Battley by Phil Battley

The dunlin is a small migratory wader that exhibits great variability in body and bill size, and plumage, leading to it being easily confused with a number of other small waders. In particular it is similar to the slightly larger curlew sandpiper, but with shorter legs and bill.  

The dunlin is a very rare vagrant to New Zealand, with four accepted records.

Identification

The dunlin is a small short-legged wader with a relatively long slightly down-curved bill. The size and bill length can vary significantly between subspecies and individuals. Females have longer bills than males. Of subspecies likely to be encountered in New Zealand the American pacifica is the largest and has the longest bill, sakhalina, which breeds in Siberia and Alaska, actites, which breeds on northern Sakhalin, kistchinskii, which breeds in far eastern Russia, and articola, which breeds in north west Alaska, are intermediate in size and bill length between pacifica  and the European subspecies. In breeding plumage the black belly is very distinctive. The crown and upper back are ruddy, with the latter scaled, the breast is streaked pale grey, the lower back and upper wings are grey and the tip of the tail is black. There is a prominent broad white supercilium. The folded wings do not reach past the tail. In non-breeding plumage dunlin have a scaly pale grey-brown back and crown, white belly and face, and a white breast with faint grey streaking. In flight dunlin display white patches on either side of the otherwise dark upper tail, and a prominent white wingbar. Their typical feeding behaviour involves vigorous probing interspersed with rapid running.

Voice: a buzzy tree.

Similar species: the bane of twitchers; dunlin can be, and has been, confused with almost every other small wader, from least sandpiper to curlew sandpiper. The black belly in breeding plumage is diagnostic. In non-breeding plumage the longer bill is sufficient to distinguish dunlin from stints.  The significantly shorter legs should be sufficient to distinguish dunlin from curlew sandpiper (Individuals of the subspecies pacifica are almost the same size as, and have a bill of similar length to, curlew sandpiper.) Dunlin also appears horizontal when feeding and roosting; in contrast to the more upright curlew sandpiper. The similar-sized white-rumped and Baird’s sandpipers have wings that extend beyond the tail. The former, with which dunlin has been known to interbreed, has a white rump. In non-breeding plumage dunlin is darker than sanderling, with less white in the wings, and has a longer bill.

Distribution and habitat

The dunlin breeds in northern Russia, Europe, Greenland, Canada and Alaska, and migrates to the coasts of southern North America, south and west Europe, north and west Africa, the Middle East, China and Japan.

Population

The dunlin is one of the world’s most abundant waders, with an estimated population between 4,600,000 and 6,500,000 birds.

New Zealand records

There are four accepted records of dunlin from New Zealand: Kaipara Harbour (February 1974), Manukau Harbour (June 1979, April-June 2006), and Miranda (March 1977). An earlier record from the Manukau Harbour (November 1969) is highly probable, and at least one additional record was never submitted for verification. All these birds had at least some dark feathers on their belly, greatly facilitating their identification. There are two confirmed records in Australia (both in Queensland).

Breeding

Dunlin breed as monogamous pairs in coastal grassland, saltmarsh, upland moorland and Arctic tundra. The clutch of 4 eggs is laid in a scrape; incubation and chick-rearing are shared, and the young leave the nest soon after hatching. Dunlin have been recorded to have interbred with white-rumped sandpiper, sanderling and purple sandpiper (C. maritima).

Behaviour and ecology

Outside the breeding season, dunlin are typically found in the company of other waders, on muddy estuaries and coastlines.

Food

Dunlin mainly eat small invertebrates (worms, crustaceans, molluscs and insects) obtained by probing. No New Zealand data.

Weblinks

http://en.wikipedia.org/wiki/Dunlin

http://www.birdlife.org/datazone/speciesfactsheet.php?id=3056

http://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=853

References

BirdLife International (2012) Species factsheet: Calidris alpina. http://www.birdlife.org (accessed on 30/9/2012)

Brown, B. 1975. Sight record of a dunlin in New Zealand. Notornis 22: 241-243.

Brown, B. 1979. Dunlin in the Firth of Thames. Notornis 26: 202-203.

Bruun, B.; Delin, H.; Svensson, L.; Singer, A.; Zetterström, D. 1986. The Hamlyn guide to birds of Britain and Europe. Revised edition. The Hamlyn Publishing Group Ltd: London.

Department of Sustainability, Environment, Water, Population and Communities (2012). Calidris alpina in Species Profile and Threats Database, Department of Sustainability, Environment, Water, Population and Communities, Canberra. Available from: http://www.environment.gov.au/sprat. (accessed on 30/9/2012).

Falla, R.A.; Sibson, R.B.; Turbott, E.G. 1978. Collin’s guide to the birds of New Zealand. 2nd edition. Collins, Auckland.

Ferguson-Lees, J.; Willis, I.; Sharrock, J.T.R. 1983. The Shell guide to the birds of Britain and Ireland. Michael Joseph Ltd, London.

Habraken, A. 1980. A dunlin at Karaka shellbanks. Notornis 27: 300-301.

Hayman, P.; Marchant, J.; Prater, A. J. 1986. Shorebirds. An identification guide to waders of the world. Christopher Helm, London.

Heather, B.D.; Robertson, H.A.; Onley, D.J. 2005. The field guide to the birds of New Zealand. 2nd edition. Penguin: Rosedale, Auckland.

Sibley, D.A. 2000. The Sibley guide to birds. Alfred A. Knopf Inc., New York.

Recommended citation

Saunders, G.C. 2012. Dunlin. In Miskelly, C.M. (ed.) New Zealand Birds Online. www.nzbirdsonline.org.nz

Dunlin

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