White-faced storm petrel

The white-faced storm petrel (Pelagodroma marina), (Māori: takahikare) also known as white-faced petrel or frigate petrel, is a small seabird of the austral storm petrel family Oceanitidae. It is the only member of the monotypic genus Pelagodroma. It is widely distributed across the northern and southern hemisphere, especially around the coastal and open ocean waters of southern Australia, New Zealand, Tristan da Cunha, Cabo Verde, the Canary islands and the Selvagens islands.

Subspecies and their distributions Here are six recognised subspecies, breeding in island colonies through subtropical to subantarctic regions of the Atlantic, Indian and south-western Pacific Oceans in both hemisphere:

P. m. albiclunis Murphy & Irving, 1951 – Kermadec Islands P. m. dulciae Mathews, 1912 – islands off southern Australia, Houtman Abrolhos in Western Australia, east to the Broughton Islands in New South Wales and Tasmania. P. m. eadesi or eadoserum Bourne, 1953– Cape Verde Islands, within the North Atlantic. P. m. hypoleuca (Webb, Berthelot & Moquin-Tandon, 1842)– Savage Islands (Selvages Islands) in the North-east Atlantic being the host the majority of the world's population of this subspecies with only 50 pairs of breeding elsewhere. An estimate from 1996 suggested a total of 61,000 breeding pairs in the Selvagens Archipelago with 36,000 counted on Selvagem Grande alone. Other breeding spots which are Canary Islands such as Montaña Clara and Alegranza. P. m. maoriana Mathews, 1912 – islands around New Zealand, including the Chatham, Auckland Islands and Whero Island. P. m. marina (Latham, 1790) – Nightingale Islands, Tristan da Cunha, Inaccessible and Gough Island (Nominate subspecies).

Description Commonly, the white-faced storm petrel is 19 to 21 centimetres (7.5 to 8.3 in) in length with a 41 to 44 centimetres (16 to 17 in) wingspan and 40 to 70 grams body mass. The key characteristics of this species include dark bill, tarsi, toes and claws. It has a pale brown to grey back, rump and wings with black flight feathers. It is white below, unlike other north Atlantic petrels, and has a white face with a black eye mask like a phalarope. Its distinctive grey-brown dorsal side plumage makes it one of the easier petrels to identify at sea from a distance. Both sexes of this frigate petrel have similar plumage with no seasonal variation. However, they have slight differences with females are larger than males in tarsus, wing and tail lengths by around 1–3%. On the other hand, males have a larger bill depth than females by about 1.7%.

While the juvenile and adult are similar, the juvenile's fresh plumage tends to have larger light fringes and tips to upperparts feathers, and depending on the moult, it may seem grey or brown. The juvenile's tail fork is also often shallower than the adult's, at least in the case of the subspecies in New Zealand, P. m. maoriana.

Certain subspecies exhibit subtle differences such as a subspecies on the Kermedec Islands, P. m. albiclunis is similar to P. m. dulciae but notable for its white rump and shorter, square tail, setting it apart from P. m. dulciae and P. m. maoriana which have pale grey rumps. The P. m. albiclunis also has white upper tail coverts instead of the usual grey that make them highly distinct. Furthermore, P. m. albiclunis have a bit smaller dimensions compared to those of P. m. dulciae. However, both of them display square tails and whitier face and breast sides than P. m. maoriana. In contrast, the white-faced storm petrel from New Zealand, P. m. maoriana has forked tail, characterized by the dark patches on the sides of the breast. It also has shorter culmen, tarsus and middle toe lengths with claw than other North Atlantic counterparts like P. m. dulciae and P. m. albiclunis. They also have longer tail than the average of other subspecies. For P. m. eadesi found in Cape Verde Islands, it has slightly paler colour of plumage than the P. m. hypoleuca, with a paler forehead and hindneck. It also has a longer beak (18–20.5 mm against 16–19 mm in P. m. hypoleuca) and whiter neck sides that create an incomplete collar.

Behaviour The white-faced storm petrel is strictly pelagic outside the breeding season, and this, together with its often-remote breeding sites, makes this petrel a difficult bird to see from land. Only in severe storms might this species be pushed into headlands. It is highly gregarious, but does not follow ships. This seabird burrows on both rocky slopes and flat sandy areas, favoring isolated islets for its nests. Like most petrels, its walking ability is limited to a short shuffle to the burrow.

Breeding

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