White-faced storm petrel

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 – 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 An estimate from 1996 suggested a total of 61,000 breeding pairs in the Selvagens Archipelago with 36,000 counted on Selvagem Grande alone. • P. m. maoriana ==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 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. 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. File:Pelagodroma marina (AM LB8146-4).jpg|alt=Young White-Faced Storm Petrel of 3 growth stages; based on the labelling, on the right is the bird that is ready to fly.|thumb|Young White-Faced Storm Petrel of three growth stages 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. ==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. There are also north Atlantic colonies on the Cape Verde Islands, Canary Islands and Savage Islands. High site fidelity observed in this species where many partners will stick together and use the same burrow year after year. 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. 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. 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. while the migration routes of eastern colonies remain unclear. P. m. eadesi This subspecies of white-faced storm petrels that breed in Cape Verde shows distinct migratory pattern from previous studies. After the breeding season, they were travelling clockwise in May and June to the northwest Atlantic and then returning to Cabo Verde or Cape Verde in October and November through the northeast. then west to South America, with data indicating that this subspecies has reached Tierra del Fuego (55°S). Foraging and flight White-faced storm petrels described as surface foragers because they often seen pattering on the water by stretching out their wings and using their long legs to lightly touch the water surface while maintaining flight. The use of pattering is significant in this Oceanitidae family but this species pattering almost all the time than other petrels. Interestingly, this species does not make extensive use of dynamic soaring to fly over the ocean surface which typically used by most other storm petrel, especially the northern storm petrels. This frequent contact with the water, combined with their foraging method, hovering with the feet briefly touching down before bounding forward, may contribute to the accumulation of gelatinous anklets on their tarsi, as observed in individuals that breed in Chatham Islands. Additionally, the formation of anklets and ligaments is more frequent due to the species' foraging strategy of hovering close to the surface with their tarsi positioned closely together. Thus, it highlights the close interaction with the surface layer of the ocean while feeding, particularly in shallow waters. Observations recorded from ships indicate that they generally forage over continental shelves while sometimes venturing near the African coast and Canary Islands, particularly during chick rearing due to high productivity. During incubation, the foraging trips average around 5.1 days with more than 700 km total distance covered by this species. Meanwhile, during chick rearing, trips shorten to 3 days covering approximately 578 km to ensure consistent feeding for their chicks. They might also primarily feed at night. Mesopelagic fish is one of their diet preferences to consume especially from Myctophidae family (FO = 71%) in the Pacific and North-east Atlantic. Meanwhile, the second biggest group diet are cephalopods (FO = 24%), most of which come from Mastigoteuthis magna species. Crustaceans like Hyperiidea and crab megalops also make up part of their diet. The majority of prey are from the surface while flying or pattering, but occasionally while resting on the surface. Interestingly, because of sexual dimorphism in which females are larger than males, they may feed their offspring larger portions. However, this may come at a higher energy cost, which could then influence the offspring's ability to reproduce and general health. It is also indicated that the species in North Atlantic may raise their chicks primarily with mesopelagic prey because they can accumulate higher mercury concentrations than nearshore species. This diet can be proved by the mercury measurements in their feathers that showed the reliance on deeper water prey during this crucial point in life stage. ==Diseases==

White-faced storm petrels are affected by a trematode Syncoelium filiferum, which uses the krill species Nematoscelis megalops as an intermediate host. The petrels appear to be an accidental or dead-end host for the larvae of the trematode, which need to attach themselves to the gill filaments of near-surface fish to continue their life cycle. Metacercariae of S. filiferum attach using sticky filaments reaching long, which adhere to the legs of the petrel and subsequently dry out as the petrels leave the water, resulting in trematode death. The petrels can become caught in vegetation and die. This phenomenon has been described among white-faced storm petrel populations in the Chatham Islands, where it reportedly causes mortality epidemics. The trematode larvae also attach to the legs of fairy prions but do not often cause bridging leg connections in that species. ==Status and conservation==

Widespread throughout its large range, the white-faced storm petrel is evaluated as Least Concern on the IUCN Red List of Threatened Species. However, certain regional populations have experienced significant declines due to habitat changes and other environmental pressures. Threats Mud Islands (P. m. dulciae) The colony of white-faced storm petrels at Mud Islands located off the coast of Victoria, Australia has been a significant population decline over the last century. Changes in habitat, vegetation, increased pressures from other species to conquer breeding areas, and human activity have all contributed to this decline. Below is the chronology happened to the decrease of Australian white faced storm petrel; During this time, the vegetation began to undergo significant changes. • 1928: The first population estimate recorded around 22,000 pairs of this subspecies on Mud Islands. • 1940s: By this period, bower spinach was no longer recorded on the islands, likely due to intense grazing pressure from European rabbits (Oryctolagus cunciculus) which eliminated the species and resulted in low-lying vegetation and increased erosion. • Mid-1980s: European rabbits were removed from the islands but significant habitat changes had already occurred. Moreover, there were other two species, coast salt bush (Atriplex cinerea) and Australian hollyhock (Lavetera arborea) showed very high in distribution and became dominant within the colony of white-faced storm petrel. Potential Threats and Population Estimates • Late 15th century: Same potential threats as previous subspecies, rabbits (Oryctolagus cunciculus) were introduced intentionally to the Salvages Archipelago when the islands were first discovered. • Unknown date: House mice (Mus musculus) have been presented on the islands for centuries was likely brought over unintentionally, posed a significant threat to the breeding colonies. • 2010s: Yellow-legged gulls consumed thousands of this petrel species almost every year. At the same time, these gulls have become a major factor in the decline of the petrel population. Furthermore, the white-faced storm petrels that live in the pelagic ecosystems of the subtropical northeast Atlantic like this subspecies are increasingly affected by plastic contamination. These birds had plastic particles in their stomachs in at least 79% of them. Research conducted through analyzing the regurgitated pellets of yellow legged gulls showed the growing impact of pollution in their environment. ==References==