VU
Providence Petrel Pterodroma solandri



Justification

Justification of Red List Category
This species qualifies as Vulnerable because it has a very small range, being confined to one very small island and one tiny islet, and it is therefore susceptible to stochastic events and human impacts.

Population justification
During the 2002 breeding season the estimated the Lord Howe Island population was estimated at just over 32,000 breeding pairs (Bester 2003). Current estimates for the Phillip Island population are at 10-100 pairs (Priddel et al. 2010) with 250 burrows counted in 2011 (N. Carlile unpub. data).

Trend justification
Surveys have determined that the species's distribution is likely to have increased since the eradication of pigs on Lord Howe Island and it appears to be establishing itself in the lower elevations south of Mt Lidgbird (Bester 2003).

Distribution and population

Pterodroma solandri breeds in the southern section of Lord Howe Island (Australia), and on Phillip Island, Norfolk Island (to Australia). It was exterminated on Norfolk Island itself between 1790 and 1800, where it was once considered numerous. One million adults and young were harvested for food from 1790-1793 and numbers dropped to 15,000 by 1796, with complete extermination by 1800 (Priddel et al. 2010). The population on Lord Howe Island was estimated at 20,000 breeding pairs in the 1970s (Fullagar et al. 1974); however a more comprehensive survey during the 2002 breeding season estimated the population at just over 32,000 breeding pairs (Bester 2003). Surveys also determined that its distribution has likely increased since the eradication of pigs on Lord Howe Island and it appears to be establishing itself in the lower elevations south of Mt Lidgbird (Bester 2003). The Phillip Island population was discovered in 1985 and numbered at least 20 birds, with current estimates of 10-100 pairs (Priddel et al. 2010) with 250 burrows counted in 2011 (N. Carlile unpub. data). Pigs, goats and rabbits all impacted Phillip Island, mainly through removal of vegetation causing large-scale soil erosion, until all were eradicated by the 1980s, since when vegetation has increased (Priddel et al. 2010). Its non-breeding distribution is across the western Tasman Sea with some dispersing to the north and northwest Pacific Ocean, perhaps as far north as the Bering Sea (Nakamura and Tanaka 1977, Cheshire and Jenkins 1981, Tanaka 1986, Marchant and Higgins 1990, J. Hobbs in litt. 2009).

Ecology

It nests in burrows or under rock cavities and occasionally between tree buttresses from sea level to 900 m, but mostly between 500 and 800 m (Bester et al. 2002, Bester 2003). On Lord Howe, it breeds in forest, as once did the population of Norfolk Island, so the Phillip Island population is atypical, burrows being in eroded cliffs of soft volcanic tuff (Priddel et al. 2010). It is a winter breeder, with birds from Phillip Island breeding at the same time as Lord Howe Island (Priddel et al. 2010). Adults arrive at Phillip from mid-April, a single egg is laid mid- to late May, hatching starts mid-July, and chicks are near-fledged by early November (Bester et al. 2007, Priddel et al. 2010). Adults land during daylight, often about 15.30 h (Priddel et al. 2010). A study on Lord Howe Island in 2000-2001 determined 54% breeding success in burrows visited twice and contents not handled, with 34-36% success in burrows repeatedly visited (Bester et al. 2007). Nests closest to burrow entrances had lowest breeding success, with the main causes of failure being flooding and predation of eggs and chicks by the endemic, threatened Lord Howe Woodhen Hypotaenidia sylvestris (Bester et al. 2007). A study in 2008 on Lord Howe Island found the breeding success in a small lowlands population to be three times higher (58%; n = 104) than in populations on Mount Gower (15%; n = 33) (D. Binder unpubl. data). Additionally, adult provisioning trips were between 2–12 days (mean 4.8), with no evidence of a bimodal distribution of long and short trips (Binder et al. 2013). The adults feed predominantly on squid and fish with crustaceans less important. The most important prey item is bioluminescent fish from the genus Electrona; maximum diving depths have been recorded at 5 m (Bester 2003). It also scavenges for food taking fish offal and has been recorded scavenging on a Shining Bronze-cuckoo Chalcites lucidus (Bester 2003). It only occasionally follows fishing boats (Kuroda 1955, Bester 2003), but some fishing material has been reported in their diet (Bester 2003).

Threats

This species is at risk from flooding due to heavy rains and the flooding of burrows represented the main cause of breeding failure on Lord Howe Island in the 2000 and 2001 breeding seasons (Bester et al. 2007). Although flooding is unlikely to kill adult birds, it kills eggs and chicks through chilling and can weaken burrows, causing them to collapse (Bester et al. 2007).

The native Lord Howe Woodhen is known to prey on eggs and young chicks and is known to be a significant source of nesting mortality (Bester et al. 2007). Wedge-tailed Shearwaters are also problematic, known to evict smaller petrels from burrows, they have been seen to kill chicks in the small population on Phillip Island (Priddel et al. 2010). Invasive and introduced species have also been a problem in the past, however, wild pigs, cats and goats have been successfully eradicated from Lord Howe Island (Department of the Environment and Energy 2015). Rat predation accounts for a small proportion of breeding failures each year (Bester et al. 2007). The rat population on Lord Howe is being controlled by baiting, with some plans to eradicate them in the future. If rat eradication does occur, introduced masked owls may switch to preying on petrels, potentially causing problematic declines (Bester et al. 2007), for this reason there are plans for the eradication of this species on Lord Howe (Milledge et al. 2010).

The Providence Petrel is at risk from drowning due to entrapment in fishing gear, however, this is not thought to be a significant source of mortality (Bester et al. 2007). Hunting is known to have severely affected the Norfolk Island population in the past, possibly causing its extirpation (Medway 2002), but is thought to be unlikely to return. Plastic ingestion may also represent a threat, with plastic found in the stomachs of over 10% of the birds sampled (Bester et al. 2010), however, this is not known to have any adverse consequences.

Conservation actions

Conservation Actions Underway

The Lord Howe Island group was designated a World Heritage Site in 1982. The control of rats has been taking place on Norfolk Island, however in 2006, the control measures were noted to be budget-constrained and limited in effectiveness (S. Garnett in litt. 2006). While a rat control programme is also ongoing on parts of Lord Howe Island (Bester et al. 2007) an eradication of all rodents is planned (Lord Howe Island Board 2009). In 2006, a proposal was submitted to eradicate all mammalian predators from all, or at least a significant part, of Norfolk Island (Holdaway 1999). Such measures might involve the establishment of an exclosure in the National Park in which all mammals are eliminated, and where chicks are translocated (Holdaway 1999, S. Garnett in litt. 2006).

Conservation Actions Proposed

Census the Lord Howe Island population at least once every five years, and the Phillip Island population every three years. Monitor breeding success on a 1-3 year basis. Eradicate cats and rat species from Norfolk Island (Holdaway 1999), or at least establish an exclusion area (Holdaway 1999, S. Garnett in litt. 2006). Consider translocation of chicks (Holdaway 1999, S. Garnett in litt. 2006). Implement bird-safe fishing practices in the Pacific Ocean fleet. Impose strict quarantine procedures on any vessels visiting Phillip Island and Lord Howe Island.

Identification

40 cm. Medium-sized, all-dark gadfly petrel. Uniform, fairly dark grey-brown with extensive whitish scaling around face and on chin, and white skua-like base to primaries on underwing. Sexually dimorphic. Males larger with significantly longer culmen (Bester et al. in press). Similar spp. Relatively long, wedge-shaped tail useful character when visible. Murphy's Petrel P. ultima has more slender bill, whiter throat, and stronger traces of "M" pattern on upperwing. Even darkest Kermadec Petrel P. neglecta has white primary shafts on upperwing. Grey-faced Petrel P. macroptera gouldi has similar face pattern, but is darker.

Acknowledgements

Text account compilers
Martin, R., Anderson, O., McClellan, R., Moreno, R., Stattersfield, A., Stuart, A., Taylor, J., Garnett, S., Fjagesund, T., Hermes, C.

Contributors
Binder, D., Carlile, N., Garnett, S. & Hobbs, J.


Recommended citation
BirdLife International (2022) Species factsheet: Pterodroma solandri. Downloaded from http://www.birdlife.org on 22/05/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 22/05/2022.