Corys Shearwater (Calonectris diomedea)

Corys Shearwater

[order] PROCELLARIIFORMES | [family] Procellariidae | [latin] Calonectris diomedea | [authority] Scopoli, 1769 | [UK] Corys Shearwater | [FR] Puffin cendre | [DE] Gelbschnabel-Sturmtaucher | [ES] Pardela Cenicienta | [NL] Kuhls Pijlstormvogel

Subspecies

Monotypic species

Genus

Until recently the shearwaters were devided in two genera Calonectris and Puffinus, but based on dna-analysis Penhallurick and Wink (2004) have proposed a splitting of the shearwaters into three genera: Calonectris for the large shearwaters of the Northern Atlantic, the Mediterranean and the waters around Japan, Ardenna for a group of large Southern Hemisphere breeders and Puffinus for the smaller shearwaters such as the Manx’ group, Audubon’s and Little Shearwaters. This new taxonomy is now widely accepted, but not by all and is stil subject of discussion.

Physical charateristics

Big pelagic seabird (L 50 cm). Upperparts brown, bill large and yellow and bellow pure white. The species breeds colonally. Nests are amongst rock crevices, recesses or burrows. Vulnerable on land, birds generally congregate offshore, forming large rafts which disperse to nesting colonies soon after nightfall. The birds feed largely on fish, cephalopods and crustaceans. Migrant.

Listen to the sound of Corys Shearwater

[audio:http://www.planetofbirds.com/MASTER/PROCELLARIIFORMES/Procellariidae/sounds/Corys Shearwater.mp3]

Copyright remark: Most sounds derived from xeno-canto

recorded by Herman van Oosten


wingspan min.: 112 cm wingspan max.: 126 cm
size min.: 45 cm size max.: 56 cm
incubation min.: 52 days incubation max.: 55 days
fledging min.: 53 days fledging max.: 55 days
broods: 1   eggs min.: 1  
      eggs max.: 1  

Range

Atlantic Ocean : widespread. Cory’s Shearwater breeds on islands and cliffs in the Mediterranean, as well as having outposts in the Atlantic at the Canary Islands (Spain), Berlengas Islands and the Azores (Portugal). After breeding, birds from the Atlantic colonies predominately winter off the east coast of North and South America. Individuals from the Mediterranean mostly winter off South Africa, and probably reach SW Indian Ocean.

Habitat

A bird of the open ocean, Cory’s shearwater is rarely seen near land, returning to barren offshore islands only to breed. Nesting occurs on cliffs, caves, rocky slopes or boulder fields, usually in areas of sparse vegetation, and nesting burrows may also be dug in soft ground. This species forages over relatively warm waters, often where a meeting of different water types brings food to the surface

Reproduction

The birds visit the colony mainly at night but are partly diurnal at some stages of their breeding cycle. In the colonies many types of nests can occur. Nests with no roof and sheltered by one wall or with deep, individual cavities were rare. Nests in a simple niche are common like nests in a short, individual cavity. Some pairs nest in caves with one or several other pairs. The distance to the nearest nest site varies between 0.2 and 6.3 m but most within a 1 meter range. Incubation lasts 52-62 days. During chick rearing, as the feeding visits of the adults become less and less frequent, there was a simultaneous decrease in visits among neighbouring nests. chick rearing lasted about 100 days and fledging occurred after bouyt 7 days.

Feeding habits

Chiefly fish, fish spawn, cephalopods, and crustaceans; also scavenges offal thrown from fishing vessels, particularly livers of cod and other oily substances. Feeds mainly at night, chiefly by skimming over surface and surface-feeding.

Video Corys Shearwater

httpv://www.youtube.com/watch?v=wmssl3nwwn0

copyright: youtube


Conservation

This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
The taxon diomedea is breeding in the Mediterranean Sea, mainly on the Balearic Islands and in the Adriatic and Aegean seas. The taxon borealis is breeding in the Atlantic Ocean, mainly at Madeira and on the Canary Islands and the Azores. It winters in the South Atlantic. The population of the European Union amounts to 135000-198000 breeding pairs, which represents about 85% of the world population of the species (Tucker & Heath). Its trends are badly known, since the species is difficult to census. An increase has been noticed in some protected colonies of Spain and the Azores. A definite decline has been reported from the Canary Islands and Madeira, however. Its main causes are predation by humans, cats, dogs, rats and mustelids, while competition with rabbits for breeding holes and disturbance by more and more invading tourism need also to be considered
Corys Shearwater status Least Concern

Migration

Migratory. Mediterranean birds mostly come out into Atlantic, where move rapidly S; abundant off South Africa, occurring Nov-May. Race borealis winters off E coasts of N and S America, and probably in SW Indian Ocean, where species recorded in large numbers, Dec-Mar; vagrant to New Zealand. Race edwardsii also leaves breeding grounds, but winter quarters unknown.

Distribution map

Corys Shearwater distribution range map

Literature

Title THE INFLUENCE OF NEIGHBOURS ON BREEDING SYNCHRONY IN
CORY?S SHEARWATER CALONECTRIS DIOMEDEA
Author(s): J-L. Mougin, C. Jouanin, M-C. Mougin & F. Roux
Abstract: The influence of neighbours on breeding synchrony ..[more]..
Source: Marine Ornithology 29: 51-56

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Title The first two cases of melanism in Cory’s Shearwater Calonectris diomedea
Author(s): BRIED, J., FRAGA, H., MIRANDA, P.C. & NEVES, V.C.
Abstract: Although aberrant colourations occur in a great va..[more]..
Source: Marine Ornithology 33: 19-22

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