South Polar Skua (Catharacta maccormicki)

Taxonomy

Monotypic
Also known as MacCormick's Skua or Antarctic Skua
 

Identification

Many skuas are difficult to identify due to extensive variation within species. Great care must be taken and many birds may ultimately not be identifiable. In the Northern hemisphere, season is often used as a criteria, however this seems dangerous given the year-round presence of non-breeding individuals. It is always worth consulting the many publications that discuss Catharacta skuas (see below), taking time to study the many published color photographs. These reveal the complex nature of the identification problem, at least more so than in idealized paintings.

South Polar Skuas are generally slightly smaller and slimmer bodied than Great Skua, with a characteristic small-headed appearance. Most show less streaking and mottling than Great Skua and lack rufous color tones. A noticably pale neck or half-collar is one of the most distinctive features. Adults usually lack the dark cap shown by adult Great Skuas, having a relatively unmarked head. There are two color-phases (or extremes) with a complete range in between. Dark birds are more common than very light birds.

Juveniles resemble adults but have a pale bluish lower mandible with a dark tip, a more gray tone to the plumage and much less pale streaking on the neck. Only hints of streaking on the mantle, scapulars and upperwing coverts. Bill pattern is similar in juvenile Great Skua.
 

Where and When

Breeds on South Shetland Islands and along the coast of Antarctica.

Non-breeders range into the Pacific, Atlantic and Indian Oceans. In the North Pacific reach as far as the Gulf of Alaska, coastal North America, Hawaii and Japan. In the North Atlantic found regularly along the eastern United States to New England and Newfoundland. Also regular of West Africa.

Photographs on the web

Nice close shot in flight Photograph by Monte Taylor, taken off California.

Adult with wing raised From the Ardery Island Project Homepage.

Series of a molting (sick?) individual discovered on the shore on Jekyll Island, Georgia, USA in October 1998. Photos by Jim Flynn. Accompanying notes by Jim Flynn and Steve Holzman
 
 

Literature

Balch, L. G. (1981) Identifying the Skuas in the ABA Area. Birding13(6): p190-201

Bearhop, S., Furness, R. and Zonfrillo, B. (1998) Identification of Catharacta skuas: variability in juvenile Great Skuas. Birding World 11(9): p355-359. More difficult news for those interested in identifying Catharacta skua at sea. The paper argues that dark juvenile Great Skuas are more frequent that previously thought, complicating the identification of Brown and South Polar Skuas. Accompanied (page 360) by an informative and thought-provoking response from Newell, Porter and Marr (authors of the paper below).

Hagelin, J. C., & G. D. Miller. (1997) Nest-site selection in South Polar Skuas: balancing nest safety and access to resources. Auk 114: 638-645.

Jiguet, F. (1997) Identification of South Polar Skua: the Brown Skua Pitfall. Birding World 10(8): p306-310

Lansdown, P. (1993) Separation of South Polar Skua from Great Skua. British Birds 86(4): p176-177

Lansdown, P. (1993) Mystery Photographs (#188) British Birds Date: 86(5): p218-219

McGeehan, A. (1998) Polar Explorations. Birdwatch Issue 75 (Sept): p28-32. Entertaining review of the status of South Polar Skua in the North Atlantic. Provides useful background to the current identification debate.

Newell, R., Porter, R. and Marr, T. (1997) South Polar Skua - an overlooked bird in the eastern Atlantic. Birding World 10(6): p229-235. Collection of photos of Catharacta skuas taken at sea off Senegal, West Africa.

Olsen, K. M. and Larsson, H. (1997) Skuas and Jaegers: A Guide to the Skuas and Jaegers of the World Date. Yale University Press.

Veit, R. R. (1978) Some Observations of South Polar Skus (Catharacta maccormicki) on Georges Bank. American Birds, 32(3): p300-302



Copyright © 1999 All rights reserved. Angus Wilson
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