| Blue petrel | |
|---|---|
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| Dorsal plumage | |
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| Ventral plumage | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Procellariiformes |
| Family: | Procellariidae |
| Genus: | Halobaena Bonaparte, 1856 |
| Species: | H. caerulea |
| Binomial name | |
| Halobaena caerulea (Gmelin, 1789) | |
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| Synonyms | |
Theblue petrel (Halobaena caerulea) is a smallseabird in the shearwater and petrelfamily,Procellariidae. This smallpetrel is the only member of thegenusHalobaena, but is closely allied to theprions. It is distributed across theSouthern Ocean but breeds at a few island sites, all close to theAntarctic Convergence zone.
The blue petrel was first described in 1777 by the German naturalistGeorg Forster in his bookA Voyage Round the World. He had accompaniedJames Cook on Cook'ssecond voyage to the Pacific.[3] Forster did not give the blue petrel abinomial name, but when the German naturalistJohann Friedrich Gmelin updatedCarl Linnaeus'sSystema Naturae in 1789 he included a brief description of the bird, coined the binomial nameProcellaria caerulea and cited Forster's book.[4] The blue petrel is now the only species placed in the genusHalobaena that was introduced for the blue petrel in 1856 by French naturalistCharles Lucien Bonaparte.[5][6] The nameHalobaena combines theAncient Greekhals,halos meaning "sea" withbainō meaning "to tread". The specific epithetcaerulea is fromLatincaeruleus meaning "blue".[7] The word "petrel" is derived fromSaint Peter and the story of his walking on water. This is in reference to the petrel's habit of appearing to run on the water to take off.[8] The species ismonotypic: nosubspecies are recognised.[6]
The blue petrel is a member of theorderProcellariiformes. It shares certain identifying features with the rest of the order. First, it has nasal passages that attach to the upper bill callednaricorns. The bills of Procellariiformes are unique in that they are split into between 7 and 9 horny plates. It also produces a stomach oil made up ofwax esters andtriglycerides that is stored in theproventriculus. This is used against predators as well as an energy-rich food source for chicks and for the adults during their long flights.[9] Finally, it also has a salt gland that is situated above the nasal passage and helps desalinate its body, due to the high amount of ocean water it drinks. It excretes a high-saline solution from their nose.[10]
The blue petrel'splumage is predominantly blue-grey, with a dark "M" extending across the upperwing from wingtip to wingtip. It has a prominent black cap and white cheeks. It is white below apart from dark patches at the side of the neck. The square tail has a white tip. It has a slender black bill. It is 26–32 cm (10–13 in) in length, has a wing span of 62–71 cm (24–28 in) and weighs approximate 200 g (7.1 oz).[11]
The blue petrel inhabits the southern oceans ranging as far north asSouth Africa,Australia and portions ofSouth America. They mostly only breed in a narrow latitudinal band from 47° to 56° S on either side of theAntarctic Polar Front, nesting onsubantarctic islands, such as theDiego Ramírez Islands, theCrozet Islands,Kerguelen Islands,Macquarie Island,South Georgia, andPrince Edward Island.[11]
In 2014, a breeding colony was discovered onGough Island (40° S, 10° W), central South Atlantic Ocean, more than 700 km north of its known and usual breeding range. Breeding here appears to take place later than at colonies farther south, so although the discovery is recent it does not necessarily represent a recent range extension.[12]
The blue petrel feeds predominantly onkrill, as well as othercrustaceans, small fish,squid and occasionally insects.[11][13] It can dive to a depth of up to 6.2 m (20 ft).[14]
The blue petrel, like all members of theProcellariiformes, iscolonial, and has large colonies. It nests in a burrow, and lays oneegg per breeding attempt. Both parentsincubate the egg for approximately 50 days, and the chickfledges after 55 days.Skuas are the main danger for their eggs and chicks.
The blue petrel has a very large range and an estimated population of 3,000,000 adult birds, and thus it is rated asLeast Concern by the IUCN.[1]
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