The white-faced storm petrel (Pelagodroma marina), () 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.Underwood, M. (2012). Does size matter? Sex differences in white-faced storm petrels' ecology (Doctoral dissertation, Deakin University).
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 , 1951 – Kermadec Islands P. m. dulciae – 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 – Cape Verde Islands, within the North Atlantic. P. m. hypoleuca – 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.Garcia-del-Rey, E. (2011). Field Guide to the Birds of Macaronesia. Azores, Madeira, Canary Islands, Cape Verde. Lynx Edicions, Barcelona. P. m. maoriana – islands around New Zealand, including the Chatham, Auckland Islands and Whero Island. P. m. marina – Nightingale Islands, Tristan da Cunha, Inaccessible and Gough Island (Nominate subspecies).Ryan, P. G., Dean, W. R. J., Moloney, C. L., Watkins, B. P., & Milton, S. J. (1990). New information on seabirds at Inaccessible Island and other islands in the Tristan da Cunha group. Marine Ornithology, 18, 43-54.
Description Commonly, the white-faced storm petrel is in length with a 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.McAllan, I. A., Curtis, B. R., Hutton, I., & Cooper, R. M. (2004). The birds of the Lord Howe Island Group: A review of records. Australian Field Ornithology, 21(Supplement), 1-82. 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.Bourne, W. R. P. (1953). On the races of the Frigate Petrel Pelagodroma marina (Latham) with a new race from the Cape Verde Islands. Bull. Brit. Om. Club, 73, 79-82.
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
The white-faced storm petrel breeds on remote islands in the south Atlantic, such as Tristan da Cunha and also Australia and New Zealand. There are also north Atlantic colonies on the Cape Verde Islands, Canary Islands and Savage Islands. It nests in dense colonies close to the sea in rock crevices and lays a single white egg. The burrows are very dense especially in forested areas where vegetation such as hollyhock and grasses help stabilize the soil, reducing the potential of burrows to collapse. It spends the rest of the year at sea and strictly nocturnal at the breeding sites to avoid predation by gulls and skuas, and will even avoid coming to land on clear moonlit nights. Other than that, to reduce the risk of predation, burrows near the edge of a colony may offer advantages as birds can land and enter their burrows faster.
The breeding period is long and varies slightly between regions. Most of the time, this seabird will return to their colonies in September or October when they clean out their burrows for Mud islands' subspecies. Then, lay the single egg in late October or November. During this period, both of the parents share incubation duties in shifts lasting 4 to 6 days with an incubation period averaging about 56 days in New Zealand colonies and about 52 days in Mud Islands. This collaborative care extends to feeding the young, which both parents do once per night. The chicks are usually abandoned shortly before fledging, occur about 52 to 67 days after hatching. Since the Mud Islands' population is a real trans-equatorial migrant, their longer travel distances to non-breeding habitats may contribute to enhanced breeding synchrony. Moreover, in these populations, breeding synchronization is frequently seen in order to capitalize on favorable climate conditions and greater food supply, which may be scarce.
High site fidelity observed in this species where many partners will stick together and use the same burrow year after year. However, this tenacity may be lower at newly established colonies like in Bass Strait. In terms of breeding cycles that highlight the asynchrony, at Mud Islands, the young typically fledged between late January and late February which is earlier than the fledging dates at Whero Island, New Zealand, about mid-February to early April. This is because Procellariform species have been shown to exhibit asynchrony, especially when they inhabit geographically separated breeding colonies.Rayner, M. J., Young, M. K., Gaskin, C. G., Mitchel, C., & Brunton, D. H. (2017). The breeding biology of northern white-faced storm petrels (Pelagodroma marina maoriana) and results of an in-situ chick translocation. Notornis, 64, 76-86. It can also be influenced by local factors like predation, habitat features or from population factors such as the quality of the bird or age structure. Overall, this species exhibits extended incubation and chick-rearing periods like other Procellariformes which further emphasizes the complexities of their breeding biology.Warham, J. (1990). The petrels: their ecology and breeding systems. A&C Black.
In some regions, white-faced storm petrels face competition for nesting sites with other seabirds. In Tasmania, studies have documented displacement by short-tailed shearwaters (Puffinus tenuirostris) from favored burrowing areas. There were also same competition have been observed on Whero Island, where the storm petrels suffered not so much from hostility by the prions, but from the fact that their nests simply happened to be in the prions' way. These interactions explain the challenges faced by these species in securing suitable nesting grounds especially when sharing habitats with larger or more dominant species.
Below is the table of different breeding cycles from different subspecies from this species:
+Breeding cycle of different subspecies of White-faced storm petrelSubspeciesColony areaReturn to colonyEgg laying PeriodHatching periodIncubation PeriodFledging PeriodFledging DurationTotal breeding periodNotable observationsP. m. albiclunisKermadec IslandsAugustMid-August to mid-late-September in southern hemisphere (in between the two North Atlantic population, P. m. hypoleuca and P. m. eadesi)Late September to early NovemberEarly November and ended in October (55 days)Fledglings may depart late November to early JanuaryUnknownLate May to December - Kermadec Islands located in a warm ocean current account for earlier breeding based on latitude - Breeding spot cleared by this population from January to May other than stragglersP. m. dulciaeMud Islands, Port Philip Bay, VictoriaEarly SeptemberEnd-October to mid-December (mean = 11 November)Mid-December to end-December (mean = 24 December)(51.7 days)Early to end-February (last chick to departure = 11 March)over 31 days (no exact period)September to mid-March (6 and a half months) - 54% eggs success hatched - 14% lost - 32% were abandoned or possibly infertile - 77.8% fledged successfully - This breeding period in Australia appeared to be more coordinated than other regions P. m. eadesiLaje Branca, Cape Verde IslandsNovemberLate January to MarchMid-March to mid-April(~47 days)Early May to mid-JuneUnknownMid-November to mid-June - 1 month earlier compared to subspecies in Selvagen Grande Island, P. m. hypoleuca. - The colonies in this population sits on the cool Canaries current account for later breedingBartholomew, J. C., & Books, T. (1990). The times concise atlas of the world. Times Books.P. m. hypoleucaSavage Islands or Salvagens IslandsMid DecemberMarch to April (mean = 17 March)Mid-May to mid-June(53.7 days)Mid-July to mid-August (last chick to departure = mid August)60.3 daysMid-December to mid-August (9 months) - Some pairs took 30% longer incubation period causes from neglected egg- The colonies in this population sits on the cool Canaries current account for later breeding and longer incubation periodsFerguson, M. W., & Deeming, D. C. (Eds.). (1991). Egg incubation: its effects on embryonic development in birds and reptiles. Cambridge University Press.P. m. maorianaWhero Island, New ZealandRichdale, L. E. (1943). The white-faced storm petrel or takahi-kare-moana (Pelagodroma marina maoriana, Mathews). Department of Zoology, University of Otago.Mid-September(Late October to late December) mean = 16 November Late-December to early February (mean = January)(~50 days)Mid-February to early-April 54 daysMid-September to mid- AprilP. m. marinaTristan da CunhaUnknownAugust to SeptemberUnknownUnknownLate December to JanuaryUnknownAugust to May
Migratory
P. m. dulciae