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Cory's Shearwater

From Opus

Cory's Shearwater (subspecies C. d. borealis)Photo by charelliAzores
Cory's Shearwater (subspecies C. d. borealis)
Photo by charelli
Azores

Includes Scopoli's Shearwater

Calonectris diomedea

Contents

[edit] Identification

C. d. diomedea (Scopoli's Shearwater): Length 45-52 cm, wingspan 112-122 cm, weight 560-730 g.
C. d. borealis (Cory's Shearwater): Length 50-56 cm, wingspan 118-126 cm, weight 817-956 g.
Light brown upper parts, white below, yellow bill with dark subterminal band, broad wings held bowed, heavy build, leisurely flight style with fewer wingbeats than other shearwaters.

Variation: the two subspecies differ slightly in plumage, with C. d. diomedea showing a little less black in the hand of the underwing due to white inner webs on the primaries, slightly smaller bill which is a little paler, overall slightly paler; the lesser overall size is not noticeable in the field. The average difference between these two forms is difficult to use because of much individual variation. More identification discussion in reference 6[6].

[edit] Similar Species

Cory's Shearwater (subspecies C. d. borealis)Photo by Glen TepkeAtlantic southeast of Hatteras, North Carolina, USA, August 2008
Cory's Shearwater (subspecies C. d. borealis)
Photo by Glen Tepke
Atlantic southeast of Hatteras, North Carolina, USA, August 2008

Cape Verde Shearwater is very similar, but slightly smaller and with a slenderer bill and relatively longer tail.
Great Shearwater is about the same size with darker wings and body, smaller bill is black, narrow straight wings, capped appearance, smudgy brown on belly (sometimes faint), and white collar.
Manx Shearwater is much smaller with blacker upperparts, and pure white belly and undertail coverts.
Balearic Shearwater is much smaller with browner underparts.

[edit] Distribution

Breeds on Atlantic islands between 28°N and 40°N, on the coast in Iberia, and on islands in the Mediterranean Sea. Post-breeding dispersal takes especially birds of subspecies borealis north of the breeding range, for example to northern Europe and to western Atlantic. Winter is spent at sea, most birds migrate to the south Atlantic and the southwest Indian Ocean.

[edit] Taxonomy

Scopoli's Shearwater (subspecies C. d. diomedea) Photo by stu78Kos, Greece, June 2009
Scopoli's Shearwater (subspecies C. d. diomedea)
Photo by stu78
Kos, Greece, June 2009

Cape Verde Shearwater was formerly included in Cory's Shearwater.

[edit] Subspecies

Two subspecies are accepted by Clements,[1] treated as distinct species by most other authorities.[2][3]

  • C. d. diomedea - (Scopoli's):
  • Breeds Mediterranean islands
  • C. d. borealis - (borealis):

[edit] Habitat

Breeds on rocky islands and steep cliffs.

[edit] Behaviour

[edit] Breeding

Colonial breeders and ground nesters; 1 egg is laid.

[edit] Diet

The diet includes molluscs and fish.

[edit] Vocalisation


Listen in an external program

[edit] References

  1. Clements, JF. 2010. The Clements Checklist of Birds of the World. 6th ed., with updates to December 2010. Ithaca: Cornell Univ. Press. ISBN 978-0801445019. Spreadsheet available at http://www.birds.cornell.edu/clementschecklist/Clements%206.5.xls/view
  2. IOC
  3. BirdLife International
  4. Wikipedia
  5. Collins Bird Guide ISBN 0 00 219728 6
  6. Identification essay about the two subspecies discussed here

[edit] External Links

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