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Long-tailed Jaeger - BirdForum Opus

(Redirected from Stercorarius longicaudus)

Alternative name: Long-tailed Skua

S. l. longicaudus, adult
Photo © by NIGHTJAR1
Spitzbergen, Norway, June 2007
Stercorarius longicaudus

Identification

Length 50–55 cm (19¾-21¾ in); (including tail projection of 12–24 cm), wingspan 105–112 cm, weight 230–350 g

S. l. longicaudus, juvenile intermediate morph
Photo © by Steve McDonnell
Goswick, Lindisfarne, Northumberland, 30 September 2017
S. l. longicaudus, juvenile dark morph
Photo © by Scottishdude
Shelford, Nottingham, UK

Adult

  • The smallest, and often the scarcest jaeger (skua)
  • Light grey-brown upperparts
  • Creamy white breast, with yellow flush on throat and cheeks
  • Grey belly
  • Black cap (which covers eyes and chin and ends at yellow nape
  • Upperwings dark-edged
  • Primaries blackish, except for white shaft only on outermost two primaries
  • Dark grey tail with black edges and very long, flexible black streamers
  • Blue-grey legs with webbed feet
  • Bill black; short and stubby compared to other jaegers
  • Sexes similar. Dark morph (similar to dark morph Parasitic Jaeger except in structure) known, but extremely rare, only a handful of records ever.

Juvenile has much shorter tail streamers than adult, but still longer than those of other juvenile jaegers; streamer tips broad, rounded. Bill grey with a dark tip. Three morphs, varying in darkness:

  • Pale morph is extensively pale grey, often with a nearly white head; only flight feathers (primaries, secondaries, rectrices) dark
  • Intermediate morph is heavily barred and spotted grey with white patches on underwings, white throat, white belly
  • Dark morph juvenile is much darker overall, with grey throat, and without white belly; only a few pale bars on under-tail coverts

Distribution

Breeds on arctic tundra of far northern areas from northern Europe (Norway eastwards), through most of arctic Asia, and Alaska, northern Canada, and Greenland.
Migration usually well offshore, but can be seen in good numbers at a few oceanic headlands, such as Ard an Runair on North Uist, Scotland.
Winters at sea, primarily between 50–60°S latitude, south of the coasts of South Africa, southern South America and Australia and New Zealand[2].

Taxonomy

Subspecies

S. l. longicaudus, adult in flight
Photo © by Kudryavtsev
Yamal, arctic European Russia, June 2006

Two subspecies are recognised[1]:

  • S. l. longicaudus
  • S. l. pallescens
  • Breeds northern North America and north-eastern Asia (white-headed juveniles are more common in this subspecies).

Habitat

Nests on Arctic tundra. Spends winters over open ocean mainly near upwelling zones at the edge of the continental shelfs, usually staying offshore, and very rarely found inland. However, in migration, and especially in central and northern Europe, a juvenile jaeger found inland on barren tundra should be considered a Long-tailed until proven otherwise.

Behaviour

Juvenile, pale morph
Photo © by Andy Hall
Isles of Scilly, UK, 18 August 2019

Diet

During the summer their main diet consists of lemmings.

Breeding

Breeding is reliant upon the availability of lemmings, its principal summer food, in almost the entire breeding range.

Vocalisation


References

  1. Clements, J. F., T. S. Schulenberg, M. J. Iliff, S. M. Billerman, T. A. Fredericks, B. L. Sullivan, and C. L. Wood. 2019. The eBird/Clements Checklist of Birds of the World: v2019. Downloaded from http://www.birds.cornell.edu/clementschecklist/download/
  2. Del Hoyo, J, A Elliot, and J Sargatal, eds. 1996. Handbook of the Birds of the World. Volume 3: Hoatzin to Auks. Barcelona: Lynx Edicions. ISBN 978-8487334207
  3. Collins Field Guide 5th Edition
  4. Birdforum thread discussing ID of a dark juvenile
  5. Furness, R.W., Kirwan, G.M., de Juana, E. & Garcia, E.F.J. (2019). Long-tailed Jaeger (Stercorarius longicaudus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/53960 on 22 August 2019).

Recommended Citation

External Links

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