White-faced storm petrel

The white-faced storm petrel (Pelagodroma marina), (Māori: takahikare)<ref name=":29">Template:Cite book</ref> also known as white-faced petrel or frigate petrel is a small seabird of the austral storm petrel family Oceanitidae.<ref name=":27">Template:Cite journal</ref><ref name=":2" /> It is the only member of the monotypic genus Pelagodroma.<ref name="Handbook of the birds of the world">Template:Cite book</ref> 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.<ref name=":21">Underwood, M. (2012). Does size matter? Sex differences in white-faced storm petrels’ ecology (Doctoral dissertation, Deakin University).

</ref><ref name=":2">Template:Cite journal</ref><ref name=":6">Template:Cite journal</ref><ref name="Handbook of the birds of the world" /><ref name=":8" />

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:<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

• P. m. albiclunis Template:Small, 1951<ref name="Murphy et al., 1951" /> – Kermadec Islands
• P. m. dulciae Template:Small<ref name="Mathews, 1912" /><ref name=":4">Template:Cite journal</ref> – islands off southern Australia, Houtman Abrolhos in Western Australia, east to the Broughton Islands in New South Wales and Tasmania.<ref>Template:Cite journal</ref><ref name=":23">Template:Cite book</ref>
• P. m. eadesi or eadoserum Template:Small<ref name="Bourne, 1953" /><ref name=":5">Template:Cite book</ref>– Cape Verde Islands, within the North Atlantic.
• P. m. hypoleuca Template:Small<ref name="Webb et al., 1842" /><ref name=":5" />– 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.<ref name=":8" /><ref>Template:Cite journal</ref> An estimate from 1996 suggested a total of 61,000 breeding pairs in the Selvagens Archipelago with 36,000 counted on Selvagem Grande alone.<ref name=":8" /> Other breeding spots which are Canary Islands such as Montaña Clara and Alegranza.<ref>Garcia-del-Rey, E. (2011). Field Guide to the Birds of Macaronesia. Azores, Madeira, Canary Islands, Cape Verde. Lynx Edicions, Barcelona.</ref>
• P. m. maoriana Template:Small<ref name="Mathews, 1912" /><ref name=":6" /> – islands around New Zealand, including the Chatham, Auckland Islands and Whero Island.
• P. m. marina Template:Small<ref name="Latham, 1790" /> – Nightingale Islands, Tristan da Cunha, Inaccessible and Gough Island (Nominate subspecies).<ref name=":19">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.</ref>

Description

Commonly, the white-faced storm petrel is Template:Convert in length with a Template:Convert wingspan and 40 to 70 grams body mass.<ref>Template:Cite journal</ref> The key characteristics of this species include dark bill, tarsi, toes and claws.<ref name=":6" /> It has a pale brown to grey back, rump and wings with black flight feathers.<ref name=":3">Template:Cite book</ref> 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.<ref name=":2" /> However, they have slight differences with females are larger than males in tarsus, wing and tail lengths by around 1 to 3%. On the other hand, males have a larger bill depth than females by about 1.7%.<ref name=":21" /><ref name=":25">Template:Cite book</ref>

File:Pelagodroma marina (AM LB8147-5).jpg

Size and look of the species from the side<ref name="Auckland War Memorial Museum">Template:Citation</ref>

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.<ref name=":26">Template:Cite book</ref> 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.<ref>Template:Cite journal</ref>

File:Pelagodroma marina (AM LB8146-4).jpg

Young White-Faced Storm Petrel of 3 growth stages<ref name="Auckland War Memorial Museum"/>

Certain subspecies exhibit subtle differences such as a subspecies on the Kermedec Islands, P. m. albiclunis is similar like 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.<ref>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.</ref><ref name=":11">Template:Cite journal</ref><ref name=":7" /> The P. m. albiclunis also has white upper tail coverts instead of the usual grey that make them highly distinct.<ref name=":10">Template:Cite journal</ref> 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.<ref name=":10" /> 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.<ref name=":11" />

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.<ref name="Bourne, W. R. P. 1953">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.</ref>

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.<ref name=":2" /> This seabird burrows on both rocky slopes and flat sandy areas, favoring isolated islets for its nests.<ref name="Handbook of the birds of the world" /> Like most petrels, its walking ability is limited to a short shuffle to the burrow.

Breeding

File:Pelagodroma marina MHNT.jpg

Egg - MHNT

The white-faced storm petrel breeds on remote islands in the south Atlantic, such as Tristan da Cunha and also Australia and New Zealand.<ref>Template:Cite report</ref><ref>Template:Cite journal</ref> There are also north Atlantic colonies on the Cape Verde Islands, Canary Islands and Savage Islands.<ref name=":2" /> It nests in dense colonies close to the sea in rock crevices and lays a single white egg.<ref name=":3" /> 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.<ref>Template:Cite journal</ref><ref name=":4" /> 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.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref name=":30" /> 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.<ref name=":4" />

The breeding period is long and varies slightly between regions.<ref>Template:Cite journal</ref><ref name=":6" /> 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.<ref name=":6" /> 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.<ref name=":6" /> 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.<ref name=":6" /> 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.<ref name="imber1984" /> 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.<ref name=":23" /><ref>Template:Cite journal</ref>

High site fidelity observed in this species where many partners will stick together and use the same burrow year after year.<ref name=":6" /><ref name=":23" /> However, this tenacity may be lower at newly established colonies like in Bass Strait.<ref name=":28">Template:Cite journal</ref> 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.<ref name=":6" /> This is because Procellariform species have been shown to exhibit asynchrony, especially when they inhabit geographically separated breeding colonies.<ref>Template:Cite journal</ref><ref name=":24">Template:Cite journal</ref><ref>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.</ref> 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.<ref name=":24" /> Overall, this species exhibits extended incubation and chick-rearing periods like other Procellariformes which further emphasizes the complexities of their breeding biology.<ref>Warham, J. (1990). The petrels: their ecology and breeding systems. A&C Black.</ref>

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.<ref name=":27" /><ref name=":28" /> 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.<ref name=":6" /> 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 petrel

Subspecies	Colony area	Return to colony	Egg laying Period	Hatching period	Incubation Period	Fledging Period	Fledging Duration	Total breeding period	Notable observations
P. m. albiclunis	Kermadec Islands	August	Mid-August to mid-late-September in southern hemisphere (in between the two North Atlantic population, P. m. hypoleuca and P. m. eadesi)<ref name=":7" />	Late September to early November<ref name=":7" />	Early November and ended in October<ref name=":7">Template:Cite journal</ref> (55 days)<ref name=":6" />	Fledglings may depart late November to early January<ref name=":7" />	Unknown	Late May to December <ref name=":7" />	- 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 stragglers <ref name=":7" />
P. m. dulciae	Mud Islands, Port Philip Bay, Victoria	Early September	End-October to mid-December<ref name=":6" /> (mean = 11 November)<ref name=":4" />	Mid-December to end-December (mean = 24 December)	(51.7 days)<ref name=":4" />	Early to end-February (last chick to departure = 11 March)<ref name=":4" />	over 31 days (no exact period)	September to mid-March (6 and a half months)<ref name=":4" />	- 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<ref name=":4" />
P. m. eadesi	Laje Branca, Cape Verde Islands<ref name=":9" />	November<ref name=":12">Template:Cite journal</ref>	Late January to March<ref name=":5" />	Mid-March to mid-April<ref name=":20">Template:Cite journal</ref>	(~47 days)	Early May to mid-June<ref name=":20" />	Unknown	Mid-November to mid-June<ref name=":20" />	- 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 breeding <ref name=":18">Bartholomew, J. C., & Books, T. (1990). The times concise atlas of the world. Times Books.</ref>
P. m. hypoleuca	Savage Islands or Salvagens Islands<ref name=":9" />	Mid December	March to April <ref name=":5" /><ref name=":8">Template:Cite journal</ref> (mean = 17 March)	Mid-May to mid-June	(53.7 days)	Mid-July to mid-August (last chick to departure = mid August)	60.3 days	Mid-December to mid-August (9 months) <ref name=":8" /><ref name=":4" />	- Some pairs took 30% longer incubation period causes from neglected egg<ref name=":8" />- The colonies in this population sits on the cool Canaries current account for later breeding and longer incubation periods<ref name=":18" /><ref>Ferguson, M. W., & Deeming, D. C. (Eds.). (1991). Egg incubation: its effects on embryonic development in birds and reptiles. Cambridge University Press.</ref>
P. m. maoriana	Whero Island, New Zealand<ref name=":13">Richdale, L. E. (1943). The white-faced storm petrel or takahi-kare-moana (Pelagodroma marina maoriana, Mathews). Department of Zoology, University of Otago.</ref>	Mid-September	(Late October to late December) mean = 16 November<ref name=":6" />	Late-December to early February (mean = January)<ref name=":6" />	(~50 days)	Mid-February to early-April <ref name=":6" />	54 days	Mid-September to mid- April<ref>Template:Cite journal</ref><ref name=":13" />
P. m. marina	Tristan da Cunha<ref name=":9" />	Unknown	August to September<ref name=":9">Template:Cite journal</ref>	Unknown	Unknown	Late December to January<ref name=":30">Template:Cite journal</ref><ref name=":9" />	Unknown	August to May<ref name=":19" />

Migratory

P. m. dulciae

Those that breed on islands from Western Australia to New South Wales mostly migrate north-west to the Arabian Sea and Indian Ocean (May to July) <ref name=":25" /> but rarely entering Indian waters (May to September),<ref>Robertson, A. L. H. (1994). Occurrence of some pelagic seabirds (Procellariiformes) in waters off the Indian subcontinent. Forktail, 10, 129-140.</ref><ref>Praveen, J., Jayapal, R., & Pittie, A. (2013). Notes on Indian rarities—1: Seabirds. Indian Birds, 8(5), 113-125.</ref> while the migration routes of eastern colonies remain unclear.<ref>Serventy, D. L. (1971). Biology of desert birds. Avian biology, 1, 287-339.</ref><ref name="Bourne, W. R. P. 1953"/><ref name=":11" /> One individual breeding on Mud Islands (Victoria) was recovered 3070 km to west,<ref name=":25" /> and documented from east to Riau Archipelago, off northern Sumatra on October<ref>Rajathurai, S. (1997). First record of white-faced storm-petrel in the Riau Archipelago. Kukila, 9, 175-176.</ref>

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.<ref name=":12" /> Then, the birds spent the non breading season in regions connected to seamounts along the mid-Atlantic Ridge and south of the Azores.<ref name=":12" />

During the non-breeding season, the species is most active at night, indicating that it benefits from the diel-vertical migration of seamount-associated nekton and zooplankton. Additionally, because of the decreased capacity to fly during the moulting season, the amount of time spent on the water before returning to the colony increased.<ref name=":12" />

P. m. marina

It migrates east to Africa, reaching southern waters around South Africa,<ref>Lambert, K. (2001). Sightings of new and rarely reported seabirds in southern African waters. Marine Ornithology, 29, 115-118.</ref> then west to South America, with data indicating that this subspecies has reached Tierra del Fuego (55°S).<ref>Montalti, D., & Orgeira, J. L. (1997). White-faced Storm Petrels Pelagodroma marina in the south-western Atlantic Ocean and south of Tierra del Fuego. Marine Ornithology, 25, 67-67.</ref><ref>Del Hoyo, J., Carboneras, C. J., Collar, N. F., & Kirwan, G. (2020). Black-browed Albatross (Thalassarche melano phris), version 1.0 in: Billerman, S. M, Keeney, B. K., Rode-Wald, P. G., & Schulenberg, T. S. Birds of the World.</ref>

Foraging and flight

File:Whitefacedstormpetrel1.jpg

The distinctive "pattering" behaviour of white-faced storm petrel on the water surface

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.<ref name=":1">Template:Cite book</ref> The use of pattering is significant in this Oceanitidae family but this species pattering almost all the time than other petrels.<ref name="Handbook of the birds of the world"/> However, during strong wind, they move like pendulum by swinging side-to-side using their feet to push off the water, facing the wind and they will glide quickly across the water with stiff extended wings and one leg lowered when moving between feeding spots.<ref name=":2" /> This behaviour is influenced by their low wing loading, low foot loading and a long tarsus that contribute to the unique frequent pattering style differentiating them in flight performance.<ref>Template:Cite journal</ref> 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.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> 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.<ref name="imber1984" /> These anklets that are composed of trematode filaments could cause them entangled in vegetation.<ref name="imber1984" /><ref>Imber, M. J. (1981). Diets of stormpetrels Pelagodroma and Garrodia and of prions Pachyptila (Procellariiformes). In Proceedings of the symposium on birds of the sea and shore. African Seabird Group, Cape Town (pp. 63-88).</ref> 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.<ref name="imber1984" />

They mainly travel for significant distances to forage, covering up to 400 km from their breeding colony.<ref name=":0">Template:Cite journal</ref> 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.<ref name=":0" /><ref>Template:Cite book</ref> 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.<ref name=":0" /> For species in north-east Atlantic, they seem to travel without strong directional preferences for any well-defined foraging hotspot during incubation explaining that they are widely distributed when finding preys.<ref name=":0" /> Additionally, this white-faced storm petrels tend to exhibit higher travel speed at night during incubation period which suggests that they may patter less frequent and feed less time during nighttime compared to the chick-rearing period. This is because the chick rearing period is more energetically demanding and thus, resulting the birds to more likely forage at both day and night time. Therefore, it leads to similar travel speeds during both periods as they increase their efforts to provide consistent feeding for their chicks.<ref name=":0" />

Diet

These white-faced petrels are opportunistic feeders in which they could consume a diverse array of prey based on availability.<ref name=":1" /> They will take fish offal that has been thrown overboard.<ref>Medway, D. G. (1997). White-faced Storm Petrel (Pelagodroma marina) eating offal. Notornis, 44, 26-26.</ref> They might also primarily feed at night.<ref name=":26" /> Studies at the Chatham Islands found the white-face storm petrels feed on a wide range of krill, amphipods, planktonic crustaceans, and small fish.<ref name=":1" /><ref>Template:Cite journal</ref> Mesopelagic fish is one of their diet preferences to consume especially from Myctophidae family (FO = 71%) in the Pacific and North-east Atlantic.<ref name=":1" /><ref>Waap, S. (2015) Trophic relationships among pelagic predators of the deep seas of the Madeira islands. Doctoral Dissertation. Cardiff University</ref> 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.<ref name=":0" /> For the petrel subspecies that breed on Chalky Island and forage in the Bass Strait, they are also known as generalist diet with a majority of individuals are feeding on coastal krill and post-larval fish.<ref name=":31">Karmalkar, M., Roman, L., Kastury, F., Arce, G. F., & Swadling, K. M. (2023). Diet assessment and vulnerability of White-faced Storm Petrel Pelagodroma marina within a warming hotspot. Marine Ornithology, 51(2).</ref> The majority of prey are from the surface while flying or pattering, but occasionally while resting on the surface.<ref>Template:Cite book</ref>

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.<ref name=":21" /> During chick rearing, since white-faced storm petrels adjust their foraging patterns to meet higher energy demands by feeding their chicks at day and night, they have been observed consuming both mesopelagic and epipelagic prey which is consistent with their dispersal throughout ocean, as mesopelagic fish are hard to access in the shallower areas.<ref>Gjøsæter, J., & Kawaguchi, K. (1980). A review of the world resources of mesopelagic fish.</ref><ref>Nybakken, J. W. (1997). Marine biology. An ecological approach. USA: Addison-Wesley Educational Publishers Inc..</ref><ref>Pusch, C., Beckmann, C., Porteiro, F. M., & von Westernhagen, H. (2004). The influence of seamounts on mesopelagic fish communities. Archive of Fishery and Marine Research, 51(1), 165-186.</ref> 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.<ref name=":16">Template:Cite journal</ref><ref name=":17">Template:Cite journal</ref> 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.<ref name=":16" /><ref name=":17" />

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.<ref name=imber1984>Template:Cite journal</ref> Metacercariae<ref name=claugher1976>Template:Cite journal</ref> of S. filiferum attach using sticky filaments reaching Template:Convert long,<ref name=imber1984/> which adhere to the legs of the petrel and subsequently dry out as the petrels leave the water, resulting in trematode death.<ref name=imber1984/> The petrels can become caught in vegetation and die. This phenomenon has been described among white-faced storm petrel populations in the Chatham Islands,<ref name=claugher1976/> where it reportedly causes mortality epidemics.<ref name=imber1984/> The trematode larvae also attach to the legs of fairy prions but do not often cause bridging leg connections in that species.<ref name=imber1984/>

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.<ref name=iucnredlist/><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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;<ref name=":21" />

• Early 1900s: The vegetation of the white-faced storm petrel was characterised as having a succulent herb land with bower spinach (Tetragonia implexicoma) as the dominant plant.<ref>Template:Cite journal</ref> During this time, the vegetation began to undergo significant changes.<ref>Template:Cite journal</ref>
• 1928: The first population estimate recorded around 22,000 pairs of this subspecies on Mud Islands.<ref name=":14">Template:Cite journal</ref>
• 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.<ref name=":14" />
• 1958: The population dropped significantly to 10,000 pairs.<ref name=":14" />
• 1978: The estimates of white-face storm petrel recorded was only 5,600 pairs indicating a continued decline.<ref name=":22">Harris, M. P. (1979). The Seabirds of the Victorian Islands: A Report to the Ministry for Conservation, Victorian StateGovernment. Natural Environment Research Council.</ref>
• Mid-1980s: European rabbits were removed from the islands but significant habitat changes had already occurred.<ref name=":4" />
  File:Oryctolagus cuniculus 115212580.jpg

  European rabbits
• 1990s: An increase in the number of other breeding bird species especially silver gulls (Larus novaehollandiae) and both Australian white ibis (Threskiornis molucca) and straw-necked ibis (T. spinicollis) resulted in further changes to the vegetation composition of Mud Islands. This also led to increased phosphorus and nitrogen levels in the soil.<ref name=":15">Yugovic, J. V. (1998). Vegetation dynamics of a bird-dominated island ecosystem: Mud Islands, Port Phillip Bay, Australia (Doctoral dissertation, Monash University).</ref> 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.<ref name=":15" />
• 2007: There were less than 2,500 pairs of this subspecies in the Islands.<ref name=":21" />
• Recent observations: Given Mud Islands' proximity to Melbourne city in Australia, white-faced storm petrel from this colony may be exposed to higher levels of plastic pollution compared to colonies in more remote locations such as Chalky Island with lower number of human population in Bass Strait.<ref name=":21" /><ref name=":31" /> The increased human activity in the nearby city likely contributes to the elevated plastic contamination observed in these birds which could further impact their health and population numbers.

South Channel Fort (P. m. dulciae)

• 1920s: White-faced storm petrels first recorded breeding in this artificial island.
• 1978: The estimated population was more than 6000 pairs.<ref name=":22" />
• Present: Population significantly smaller.

Potential Threats

• The invasive African boxthorn (Lycium ferocissimum) spread across the island, resulting in some petrels and silver gulls getting stuck on the thorns.
• Few of this subspecies have been discovered drowning in gun emplacements or stuck in the tunnel system
• Human visitors trampling burrows, causing disturbance.<ref name=":22" />

Tullaberga Island (P. m. dulciae)

• 1978: Estimated population was over 21,000 pairs, being the biggest colony of this species in Victoria
• Present: The population has probably decreased, and the status was unclear.<ref name=":21" />

Potential Threats

• Increased population of short-tailed shearwaters (Puffinus tenuirostris) potentially competing with white-faced storm petrels for nesting areas.

Conservations

• No visitor could access to the island to protect the seabird populations there.<ref name=":21" />

Savage Islands (P. m. hypoleuca)

For this subspecies, due to its restricted breeding range which primarily nests in the Salvages Archipelago in the north-east Atlantic, they are considered vulnerable and has been designated as "Species of European Conservation Concern".<ref>Tucker, G., & Heath, M. (1994). Birds in Europe: Their conservation status. BirdLife Int. BirdLife Conservation Series, (3), 1-600.</ref>

File:Atlantic Yellow-legged Gulls (4990020070).jpg

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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.<ref>Template:Cite book</ref>
• 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.<ref name=":8" /> Another concerning potential threats were the petrel predators that can prey on the storm petrel called yellow-legged gulls, expanding in the population few years ago.<ref>Mougin, J. L., & Stahl, J. C. (1981). Le régime alimentaire des Goélands argentés Larus argentatus atlantis de’île Selvagem Grande. Cyanopica, 2(3), 43-48.</ref><ref>Zino, F., & Biscoito, M. (1994). Breeding seabirds in the Madeira archipelago. Seabirds on islands. Threats, case studies and action plans. BirdLife International Conservation Series, (1), 172-185.</ref>
• 2010s: Yellow-legged gulls consumed thousands of this petrel species almost every year.<ref>Catry, P., Geraldes, P. L., & Almeida, A. (2010). Seabirds of Selvagem Pequena and Ilhéu de Fora: censuses and notes, with data on the diet of the Yellow-legged Gull. Airo, 20, 29-35.</ref><ref>Template:Cite journal</ref> 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.<ref name=":32">Template:Cite journal</ref> Research conducted through analyzing the regurgitated pellets of yellow legged gulls showed the growing impact of pollution in their environment.<ref name=":32" />

External links

• BirdLife Species Factsheet
• The white-faced storm petrel discussed in RNZ Critter of the Week, 24 Jul 2020