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Black-throated Diver

Black-throated Diver (Gavia arctica), known in North America as Arctic Loon, is a medium-sized member of the loon or diver family.

Description

Breeding adults are 63 cm to 75 cm in length with a 100 cm to 122 cm wingspan, shaped like a smaller, sleeker version of the Great Northern Diver. They have a grey head, black throat, white underparts and chequered black-and-white mantle. Non-breeding plumage is drabber with the chin and foreneck white. Its bill is grey or whitish and dagger-shaped. In all plumages a white flank patch distinguishes this species from all other divers including the otherwise almost identical Pacific Diver.

Distribution

It breeds in Eurasia and occasionally in western Alaska. It winters at sea on large lakes over a much wider range.

Behaviour

This species, like all divers, is a specialist fish-eater, catching its prey underwater. It flies with neck outstretched.

The call is a yodelling high-pitched wail.

Miscellaneous

The Black-throated Diver is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.

Instructions for constructing and deploying artificial floating islands to provide Black-throated Divers with nesting opportunities are given in Hancock (2000).

On September 6, 2007, RSPB Scotland and the Scottish Natural Heritage (SNH) stated that it was surprised by an increase in the last 12 years in the breeding figures in the UK for the Red-throated Diver and the rarer Black-throated Diver of 16% and 34% respectively due to the anchoring of 58 man-made rafts in lochs. Both species decreased elsewhere in Europe.

Dr Mark Eaton, RSPB scientist traced the drop in overall numbers to warming of the North Sea which reduced stocks of the fish on which they feed.

References

  • Hancock, Mark (2000): Artificial floating islands for nesting Black-throated Divers Gavia arctica in Scotland: construction, use and effect on breeding success. Bird Study 47: 165-175. HTML abstract
  • Harrison, Peter (1988): Seabirds (2nd ed.). Christopher Helm, London ISBN 0-7470-1410-8
  • National Geographic Society (2002): Field Guide to the Birds of North America. National Geographic, Washington DC. ISBN 0-7922-6877-6

External links

Further reading

The following articles deal with separation of Pacific Diver from Black-throated Diver:

  • Birch, A. and Lee, C-T, 1997, Field identification of Arctic and Pacific Loons, Birding 29: 106-115.
  • Birch, A and Lee, C-T, 1995, Identification of the Pacific Diver - a potential vagrant to Europe, Birding World 8: 458-466.

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