LC
Bonin Petrel Pterodroma hypoleuca



Justification

Justification of Red List Category
This species has a very large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

Population justification
Brooke (2004) estimated the global population to approach c.1,000,000 individuals, while the population in Japan has been estimated at c.100-10,000 breeding pairs and c.50-1,000 individuals on migration (Brazil 2009).

Trend justification
The population is suspected to be in decline owing to predation by invasive species.

Distribution and population

The Bonin Petrel disperses widely over the subtropical north Pacific, nesting on Bonin and Volcano Island (Japan) and on the western Hawaiian Islands (U.S.A.) (del Hoyo et al. 1996).

Ecology

This species rarely approaches land except at colonies, feeding mostly at night on a diet predominately comprised of fish, as well as some squid, shrimps and sea skaters. It breeds on oceanic islands, creating burrows in areas of sandy soil or high sloping ground up to 918 m, usually amongst vegetation. Breeding starts in December, with individuals forming dense colonies (del Hoyo et al. 1996).

Threats

This species is threatened by climate change, having been identified as highly vulnerable to sea-level rise throughout the Hawai’ian Islands. Passive sea-level rise has been modelled to reduce the future carrying capacity for the species on Midway Island (Reynolds et al. 2015), with impacts from flooding predicted to cause further mortality and nest losses (Reynolds et al. 2015).

Three of the main invasive species known to have caused declines in the Bonin Petrel, the European Rabbit Oryctolagus cuniculus, House Rat Rattus rattus and Polynesian Rat Rattus exulans, have been eradicated from much of its range, with rapid population increases after eradication events (Rauzon 2007, Taylor 2017). House Rats remain a problem in some of the Japanese range, although this holds less than 5% of the global breeding population (Carboneras et al. 2018). House Mice Mus musculus predate on Bonin Petrels in some parts of its range, however, baiting and trapping is taking place to control the population and eradication is planned for 2018/19.

Acknowledgements

Text account compilers
Butchart, S., Fjagesund, T., Calvert, R., Hermes, C., Ekstrom, J., Martin, R., Stuart, A.


Recommended citation
BirdLife International (2019) Species factsheet: Pterodroma hypoleuca. Downloaded from http://www.birdlife.org on 17/07/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 17/07/2019.