Data Zone
Justification of Red List category
This recently described species is listed as Critically Endangered because it is thought to have an extremely small population, which is inferred to be declining as a result of predation by introduced mammals.
Population justification
The species's population size has not been quantified, but given its apparent rarity it is thought to have an extremely small population, probably numbering fewer than 250 mature individuals. The population is therefore placed in the band 50-249 mature individuals, assumed to equate to a total population of c.70-380 individuals.
Trend justification
The population is inferred to be in decline owing mainly to predation by introduced rats (Kawakami et al. 2012, Fjeldså 2013).
The species is currently only known from individuals found in burrows on Midway Island in the north-western Hawaiian chain, U.S.A., and in the Bonin Islands (Ogasawara Islands), Japan. The species was described from an individual collected in 1963 on Midway Island, with another individual of this species observed on Midway during the winters of 1990-1991 and 1991-1992. It is considered unlikely that the species is regularly breeding on Midway or other Hawaiian atolls, as the seabird colonies there have been studied in detail and appropriate natural breeding habitat is lacking (Pyle et al. 2011, 2014). Subsequent analysis of specimens from the Bonin Islands suggests that its main breeding range is within that group, although much exploration is still to be done (Kawakami et al. 2012). In February 2015, 10 birds and at least one nest were discovered on Higashijima in the Bonin Islands (Forestry and Forest Products Research Institute 2015), after calls were detected there and on other Bonin Islands with passive acoustic sensors in 2012-2014. Prior to 2012, five of the six individuals recorded on the Bonin Islands had been corpses, three of which had been predated by Black Rats Rattus rattus (Kawakami et al. 2012, Fjeldså 2013). The at-sea distribution is effectively unknown, although at minimum it transits through the tropical or subtropical waters of the central western Pacific Ocean between the north-western Hawaiian chain and the Bonin Islands. Its apparent rarity suggests that the population is extremely small.
Very little is known about this species. It breeds during the boreal winter, as the specimens found so far on land and calling from burrows and nesting have been in the period December to May (Kawakami et al. 2012, Fjeldså 2013, Pyle et al. 2014). The nesting individuals recorded on Higashijima in February 2015 were found in a mosaic of scrub forest and grassland, consisting of Screw Pine Pandanus boninensis and Bonin Silver Grass Miscanthus boninensis (Forestry and Forest Products Research Institute 2015). The nest site was a burrow in grassland. The individual recorded on Midway Atoll in 1991 was found in a crevice in rocky habitat (Pyle et al. 2014). To date, it has only been found on small islands. It may co-utilize nesting sites with Bulwer's Petrel Bulweria bulwerii (Pyle et al. 2014).
Introduced Black Rats Rattus rattus pose a considerable threat to the species, being present on more than 20 islands in the Bonin group (Kawakami et al. 2012). On Higashijima Island, three carcasses of Bryan’s Shearwater were found that had been depredated by rats and it is suspected that the paucity of records of the species may be a result of rat predation (Kawakami et al. 2012, Fjeldså 2013). Predation of smaller seabirds by rats on Higashijima dramatically increased in 2005, attributed to a shift in the foraging behaviour of the rats (Kawakami et al. 2012). The Ministry of Environment responded to the mass depredation of small petrels by initiating a rat eradication program on Higashijima in 2008, which has apparently been successful, with no rats observed since 2010 (Kawakami et al. 2012). Rats are also absent from Kitanoshima Island, but remain in large parts of the species’ range. Eradication of rats from these islands would be necessary for these areas to be suitable as breeding locations (Kawakami et al. 2012, Fjeldså 2013). Invasive plant species, Casuarina equisetifolia and Leucaena leucocephala, may also have impacted breeding success on Higashijima, as they invade the breeding habitat and alter the environment (Forestry and Forest Products Research Institute 2015). The Forest Agency has eradicated almost all matured C. equisetifolia so far and is conducting an eradication program for L. leucocephala. Light pollution is another potential threat. It is a significant cause of mortality in Newell’s Shearwater Puffinus newelli, and two of the six P. bryani specimens that were located in the Bonin Island prior to 2015 were collected after apparent disorientation due to artificial lighting.
Conservation Actions Underway
Higashijima is an IBA. It is protected by the Forestry Agency and access to the island is restricted (Forestry and Forest Products Research Institute 2015). Rats have already been eradicated on Higashijima, following a program of poisoned bait application between 2008 and 2010 (Kawakami et al. 2012). Currently, there is an eradication programme ongoing , as detailed for each island in the Ogawasara Islands Ecosystem Conservation Action Plan (Anon. 2010). Work is ongoing to remove introduced plant species on Higashijima. A careful investigation of known seabird colonies in the subtropical/tropical western Pacific may reveal additional records. Street lights that reduce light pollution have been installed in residential areas in the Bonin Islands to reduce disturbance to the species (Forestry and Forest Products Research Institute 2015).
Conservation Actions Proposed
Survey seabird colonies on Higashijima and Kitanoshima to confirm additional breeding sites for this species. Examine other known seabird colonies in the subtropical west Pacific for evidence of this species, in particular northern Marianas, Nihoa and Necker Islands and the north-west Hawaiian islands with habitats that support Bulwer's Petrel which may co-utilize breeding crevices with Bryan's Shearwaters (Pyle et al. 2014). Ensure Higashijima is free of rats. Eradicate rats, goats and pigs from all small islands in the Bonin group. Although feral goats and pigs have already been eradicated from all uninhabited small islands in the Bonin Islands, feral goats continue to exist on the inhabited Chichijima Island. Study the ecology and distribution of the species; more information is needed on their at-sea biology (Pyle et al. 2014).
c. 25 cm. Smallest of all Puffinus shearwaters but very similar to P. boydi especially, being slaty black above with white underparts including the lores, supercilliary region and ear coverts. The undertail coverts are blackish. Similar species. P. boydi very similar, but has considerably longer tarsi and shorter tail as well as white undertail coverts.
Text account compilers
Ashpole, J, Martin, R., Hermes, C., Moreno, R., Fjagesund, T., Stuart, A., Symes, A., Taylor, J.
Contributors
Kawakami, K., Pyle, P.
Recommended citation
BirdLife International (2024) Species factsheet: Bryan's Shearwater Puffinus bryani. Downloaded from
https://datazone.birdlife.org/species/factsheet/bryans-shearwater-puffinus-bryani on 22/12/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 22/12/2024.