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Arctic Tern

From Opus

Breeding adult Arctic Tern Photo by mikemikAkureyri, Iceland, August 2007
Breeding adult Arctic Tern
Photo by mikemik
Akureyri, Iceland, August 2007
Sterna paradisaea

Contents

[edit] Identification

Common tern is on the left, Arctic on the rightPhoto by Steve G
Common tern is on the left, Arctic on the right
Photo by Steve G

Length 33–36 cm (13-14ΒΌ in), mass 76-116 g.
Breeding adult: Black forehead, nape and crown and white cheeks; the mantle, back and upper wings are grey and the collar, rump and underwing are white. The deeply forked tail is white with grey outer webs. The long bill, legs and feet are red.
Non-breeding adult and immature: Forehead white, crown streaked black and white, nape black. The bill is black and the legs and feet dark red to blackish.

[edit] Similar Species

Immature Arctic Tern Photo by the late Jim WoodShetland Islands
Immature Arctic Tern
Photo by the late Jim Wood
Shetland Islands

Common and Arctic Terns are a species pair easily confused.
On the ground the short legs of Arctic Terns give them a somewhat huddled look whilst the tail feathers in summer birds extends well beyond the folded wings. Common Terns stand taller and the tail feathers do not extend past the primaries.
On flying birds the wing of Arctic when seen against the light is really quite translucent whereas in Common only the inner primaries are translucent. Common Terns have a black wedge or notch effect on the upper outer 5/6 primaries which is absent in Arctic and the trailing black edge of the primaries is narrower and neater in Arctic.
I find the easiest way to separate them in summer is by the fact that Arctics have a very buoyant bouncy flight and are more compact in the head and neck coupled with the long tail giving the impression that the wings are well-forward on the body whereas Common Terns seem to have their wings more to the centre of the bird. The real clincher however is the beak - Common Tern has a fairly long orange-red beak with a clear black tip whilst Arctic Terns have a shorter solid blood-red beak (and are more likely to draw blood when you invade the nesting colony!!) Written by Steve G

On real close ups, look for the colour of the crescent under the eye; black in Arctic Tern, white in Common, creating different impressions on completeness of the mask.

[edit] Distribution

ChickPhoto by flyshopAnchorage, Alaska, June 2017
Chick
Photo by flyshop
Anchorage, Alaska, June 2017

Breeds in arctic and sub-arctic Europe, Asia, and North America. Truly phenomenal migration, by far the longest distance for any bird, allowing it to get two summers per year. Birds breeding around the North Sea (including the Farne Islands in Northumberland, and the Netherlands) first fly to a staging area in the central North Atlantic around 1000 km NNW of the Azores, feeding there for a week or two, then down the mid Atlantic to the cool waters west of South Africa to stage there for another 2-3 weeks; after that, flying ESE to the Southern Ocean south of Australia and New Zealand before turning south to the Antarctic pack-ice off Wilkes Land, East Antarctica for their second summer of the year. They then return first west off the Antarctic coast, then north by the same route as southbound; individual birds flew up to 96,000 km per year[3][4]. The speed of migration is remarkable too, with one juvenile ringed as a chick on the Farne Islands, UK reaching Melbourne, Victoria, Australia in less than 4 months from fledging[5]. Birds breeding in Greenland travelled slightly shorter routes, to the Atlantic coast of Antarctica, not going east to Australia and "only" covering up to 70,000 km[6].

Accidental in continental interior locations such as Kansas.

[edit] Taxonomy

This is a monotypic species[7].

[edit] Habitat

Oceans. Nests on islands in the Arctic.

[edit] Behaviour

[edit] Diet

The diet includes fish and small marine invertebrates.

[edit] Breeding

The nest is a depression in the ground and 1-3 mottled eggs are laid. Both parents incubate the eggs for 27 days; the young fledge after 21–24 days.

[edit] Longevity

Long-lived, up to 34 years[8], so individuals may be travelling over 3 million km (2 million miles) in a lifetime - equivalent to four return trips to the Moon.

[edit] Vocalisation


Listen in an external program

[edit] References

  1. Hockey, PAR, WRJ Dean, and PG Ryan, eds. 2005. Roberts' Birds of Southern Africa. 7th ed. Cape Town: John Voelcker Bird Book Fund. ISBN 978-0620340533
  2. Wikipedia
  3. Record-breaking bird migration revealed in new research. Newcastle University press release.
  4. Fijn, R. C., et al. (2013). Arctic Terns Sterna paradisaea from The Netherlands migrate record distances across three oceans to Wilkes Land, East Antarctica. Ardea 101 (1): 3-12.
  5. Birds in Northumbria 1982 Northumberland Bird Report.
  6. Egevang, C., et al. (2010). Tracking of Arctic terns Sterna paradisaea reveals longest animal migration. PNAS 107: 2078–2081.
  7. Clements, J. F., T. S. Schulenberg, M. J. Iliff, D. Roberson, T. A. Fredericks, B. L. Sullivan, and C. L. Wood. 2016. The eBird/Clements checklist of birds of the world: v2016, with updates to August 2016. Downloaded from http://www.birds.cornell.edu/clementschecklist/download/
  8. AnAge entry for Sterna paradisaea
  9. Birdforum thread discussing separation of Common vs Arctic Terns and mentioning eye crescent in post #12

[edit] External Links


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