| Snow petrel | |
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Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Procellariiformes |
| Family: | Procellariidae |
| Genus: | Pagodroma Bonaparte, 1856 |
| Species: | P. nivea |
| Binomial name | |
| Pagodroma nivea (Forster, G, 1777) | |
| Subspecies[2] | |
P. nivea nivea(G. Forster, 1777) | |
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range | |
Thesnow petrel (Pagodroma nivea) is the only member of the genusPagodroma. It is one of only three birds that have been seen at the GeographicSouth Pole, along with theAntarctic petrel and thesouth polar skua, which has the most southerly breeding sites of any bird, inland in Antarctica.[3]
The snow petrel wasdescribed 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.[4]
We particularly observed a petrel, about the size of a pigeon, entirely white, with a black bill and blueish feet; it constantly appeared about the icy masses, and may be looked upon as a sure fore-runner of ice.[4]
Forster placed the snow petrel in thegenusProcellaria that had been erected for the petrels byCarl Linnaeus in 1758 and coined thebinomial nameProcellaria nivea.[4][5] The snow petrel is now the only species placed in the genusPagodroma that was introduced for the snow petrel in 1856 by French naturalistCharles Lucien Bonaparte.[6][7] The genus name combines theAncient Greekpagos meaning "frost" or "sea-ice" withdromos meaning "racer" or "runner". The specific epithet is from theLatinniveus meaning "snow-white".[8] The word "petrel" is derived fromPeter the Apostle 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.[9]
Snow petrels vary significantly in size with two different forms, a larger and a smaller.[10] The two forms hybridise extensively and this has led to uncertainty about the taxonomic status and the precise geographic distribution of the different types.[11][12] In 1857 Bonaparte in hisConspectus Generum Avium listed subspeciesmajor andminor but as he provided no further information, these names are not recognised and are considered asnomen nudum.[13] The German ornithologistHermann Schlegel in 1863 provided descriptions for the subspeciesminor andmajor but erroneously believed that Forster's original description applied to the larger form.[14] In 1912Gregory Mathews, in the second volume of hisBirds of Australia, treated the larger form as a separate species and introduced the binomial namePagodroma confusa.[15] The two forms are now usually treated as subspecies and Schlege is acknowledged as the authority for the larger subspecies.[7][12][16]
The snow petrel is a member of thefamilyProcellariidae, and theorderProcellariiformes.[7] They all share certain identifying features. First, they have nasal passages that attach to the upper bill callednaricorns. The bills of Procellariiformes are also unique in that they are split into seven to nine horny plates. They produce astomach oil made up ofwax esters andtriglycerides that is stored in theproventriculus. This can be sprayed out of their mouths as a defense against predators (principallyskuas)[17] and as an energy-rich food source for the chicks and for the adults during their long flights.[18] Finally, they also have asalt gland situated above the nasal passage which helps desalinate their bodies, due to the high amount of ocean water that they imbibe. It excretes a high saline solution from their nostrils.[19]
Two subspecies are recognised:[7]
The snow petrel is a small, pure whitefulmarine petrel with coal-black eyes, a small black bill and bluish gray feet. Body length is 30–40 cm (12–16 in) and the wingspan is 75–95 cm (30–37 in). Flight is erratic with frequent changes of direction.[20]
Snow petrels are almost entirely restricted to cold Antarctic waters. Flocks are characteristically seen sitting on icebergs.
Breeding occurs incolonies on the Antarctic continent and on various Antarctic islands. Nesting is colonial in small to large colonies on exposed rocks, usually near the sea, but also on inland mountain ranges more than 400 km (250 mi) from the open sea.[20][21][22] Some birds remain at the colony all year, but the main influx at colonies is from the mid-September until early November. Nests are simple pebble-linedscrapes usually in a deep rock crevices with overhanging protection. Nests are abandoned if concealed by heavy snowfall; egg mortality is 50%, and chick mortality is 10–15%.[17] One whiteegg is laid between late November and mid-December. The egg isincubated 41 to 49 days and the chick isbrooded for 8 days. Theyfledge 7 weeks later in late February to mid-May. Colonies are also the sites of cleaning areas where snow petrels, far from the sea, bathe in snow.[citation needed]
Snow petrel partners are faithful for life (around 20 years).
Snow petrels feed mainly on fish, somecephalopods,mollusks, andkrill, as well ascarrion in the form of sealplacentas, dead/stillborn seals, whale carcasses, and dead penguin chicks.[17] During the winter, they disperse to thepack ice, ice floes, and the open sea. Flocks are characteristically seen sitting on icebergs. Only very rarely are they observed north of the pack ice.[23]
The snow petrel has an occurrence range of 35,900,000 km2 (13,861,067 sq mi), and an estimated population of 4 million adult birds. Based on these numbers, theIUCN has classified this bird asleast concern.[24]
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