Blue Petrel (Halobaena caerulea)

[order] PROCELLARIIFORMES | [family] Procellariidae | [latin] Halobaena caerulea | [authority] Gmelin, 1789 | [UK] Blue Petrel | [FR] Prion bleu | [DE] Blau-Sturmvogel | [ES] Petrel Azulado | [NL] Blauwe Stormvogel

Subspecies

Genus

Physical charateristics

The Blue Petrel is a small petrel with a wing span of about 65 cm. It is the only small petrel with a square white tail-tip. Its dark crown extends to below the eye, down the nape and forms a large dark patch on the side of the neck. The forehead, throat and ear-notch are a contrasting white. The Blue Petrel is blue-grey above and white below (including underwings). A conspicuous dark M-shaped band crosses the blue-grey upperwings. The tail is blue-grey with a narrow sub-terminal dark band and conspicuous square white tip. The legs and feet are blue with pink webs

Range

Southern Ocean : widespread. The Blue Petrel is found throughout southern Oceans. Breeding sites include the Crozet Islands and Kerguelen Island (French Southern Territories), Marion Island and Prince Edward Island (South Africa), Macquarie Island (New Zealand) and South Georgia (Georgias del Sur ). Adults are perhaps mainly sedentary, though young birds are more dispersive.

Habitat

The Blue Petrel is marine species of the Subantarctic and Antarctic seas. In summer, it occurs mainly over waters of -2 to 2 degrees C in surface temperature, but it also ranges south to the edge of the pack-ice and north to approximately 30 degrees south, or further north over cool currents. It prefers open water. In the Antarctic, it generally avoids the pack-ice, and only occasionally approaches the edge of the ice.

Reproduction

The Blue Petrel nests in rock crevices or burrows in deep, dry soil with low vegetation. Its burrows extend 15 to 37 cm below the surface, and are about 6 cm in diameter, 30 to 100 cm long and they end in nest chambers that are around 18 cm in diameter. Its burrow entrances are larger than those of Salvin’s Prions Pachyptila salvini. The Blue Petrel sometimes lines its chambers with fibres, leaves or twigs. The Blue Petrel lays a single egg. Its incubation period is 45 to 52 days, and its nestling period is 43 to 60 days. It breeds in dense but discrete colonies. It returns to burrows in late August to September and generally lay eggs in mid to late October, but sometimes as early as September. Chicks fledge and depart between late January and early February.

Feeding habits

The Blue Petrel eats mainly pelagic crustaceans, fish and cephalopods (octopus and squid). It sometimes eat insects, but rarely eats vegetable matter. The relative importance of dietary items varies with locality. The types of crustaceans eaten are mainly euphausiids, but it also eats amphipods, and some decapods and other crustaceans. The breeding diet consisted of 58% fish, 41% crustaceans and 1% squid by weight during a study at South Georgia Island, and 3% fish, 92% crustaceans, 2% cephalopods, and 3% insects by frequency at Marion Island.

Video Blue Petrel

httpv://www.youtube.com/watch?v=nXe_yap6ISI

copyright: Peter Fraser

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). The population trend appears to be stable, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is extremely 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 Blue Petrel has a circumpolar distribution, ranging south to the pack-ice and north to about 30 degrees south. It reaches 20 degrees south in the Humboldt Current off Peru in winter. It is an uncommon winter and spring visitor to Australia and New Zealand.

Migration

The timing of movements of the Blue Petrel away from breeding grounds is poorly documented, and adults may be largely sedentary. Poulation declines coincide with exceptional cyclonic conditions to the southwest of the Australian continent, which forces birds northwards. The Blue Petrel departs breeding colonies following fledging between late January and early March. Adults may disperse only to adjacent waters, especially initially. Adults have been recorded at some breeding colonies until June, and at Macquarie Island, adults occasionally return to nesting chambers throughout winter. Non-breeding Blue Petrels move north from the pack-ice in winter to about 30 degrees south, and up to 20 degrees south off the coast of Peru. The Blue Petrel is present off the coast of South Africa between June and December with a peak in September. It begins to return to breeding colonies late in August and early September, and probably remains north of the Antarctic Polar front in summer.

Distribution map