Justification of Red List Category
The prevalence of threats from introduced predators on the species's main breeding grounds in Japan and additional factors such as fisheries bycatch and human disturbance suggests that the species is in overall decline. It is therefore precautionarily classified as Near Threatened as it almost meets the requirements for listing as threatened under criteria A2abe+3be+4abe. Further data are required from across its range to quantify the trend.
Brooke (2004) estimated the global population to number c.3,000,000 individuals, while national population estimates include: c.100-10,000 breeding pairs, c.50-1,000 individuals on migration and c.50-1,000 wintering individuals in China; c.100,000-1,000,000 breeding pairs, c.10,000 individuals on migration and c.10,000 individuals on migration and c.50-1,000 wintering individuals in Japan and c.10,000-100,000 breeding pairs and c.1,000-10,000 individuals on migration in Russia (Brazil 2009).
The population is suspected to be undergoing a moderately rapid decline, owing primarily to predation by introduced mammals (S. Uematsu in litt. 2012).
This species is found in the western Pacific, breeding on the coast and on offshore islands of Japan, Russia, and on islands off the coasts of China, North Korea and South Korea. It migrates south during winter, being found off the coasts of Vietnam, New Guinea, the Philippines, Australia, southern India and Sri Lanka (del Hoyo et al. 1992, Praveen et al. 2013). The global population has been estimated to number c. 3,000,000 individuals (Brooke 2004). In Japan, where the majority of the species’s world population breeds, there are 11 islands that are each thought to be inhabited by more than 10,000 breeding pairs (Oka 2004). A recent survey on the island of Nakanokamishima estimated the population at 5,566 individuals and 2,783 nests (Yamamoto et al. 2015). According to islanders, the species appears to have been declining rapidly on Mikura-Jima, but quantitative data are not available (S. Uematsu in litt. 2012). The prevalence of threats from introduced predators suggests that the species is in overall decline; however, further data are required from throughout the species’s range to assess the current population trend.
This marine species can be found over both pelagic and inshore waters. It feeds mainly on fish and squid which it catches by surface-seizing and shallow plunges. It often associates with other seabirds and will follow fishing boats. Breeding begins in March in colonies on offshore islands, occupying burrows on forested hills. It undergoes transequatorial migration (del Hoyo et al. 1992).
Introduced mammals poses the greatest threat to the population, with cats Felis catus and rats Rattus norvegicus and R. rattus being present throughout the species’s range. Rats have invaded at least three of the Japanese breeding islands, with current impacts largely unknown, but likely to affect fledgling success and egg predation (Lee 2010). The shearwaters appear to suffer significant impacts from rats on Mikura-Jima, which is populated by c.300 people and is popular with tourists, thus making an eradication programme problematic and the subsequent reintroduction of rats more likely (Oka et al. 2002, J. Croxall in litt. 2011). Feral cats may also be inflicting increasing mortality on the Mikura-Jima population through predation on chicks, young birds and adults (N. Oka per M. Sato in litt. 2012, S. Uematsu in litt. 2012). Efforts are being taken to capture and neuter feral cats, however due to pressure from the public, cats are hard to eliminate.
Currently, climate change is affecting foraging distribution and hence energetic budgets of adults. It is further predicted that whole colonies may be affected in the future as prey populations shift distribution in response to climate change.
In addition to these threats, the species is also susceptible to fisheries bycatch (Birds Korea 2010, J. Croxall in litt. 2011), but the impact has not been quantified.Research suggests the Fukushima nuclear accident may have had negative impacts on birds breeding on Mikura Island, with reduced vitamin A levels detected in chicks following the release of radioactive material (Uematsu et al. 2014). The researchers suggest that additional negative impacts may be expected in the population in the future.
Conservation and Research Actions Underway
On Mikura-Jima, some management actions have been carried out to control cats (both feral and domestic); these have included neutering and subsequent release (N. Oka per M. Sato in litt. 2012).
Conservation and Research Actions Proposed
Monitor population trends at selected breeding sites throughout its range. Quantify the impacts of introduced predators on all affected breeding islands, and study the potential impact of fisheries bycatch. Implement robust control measures and strengthen existing management actions to alleviate, and if possible eliminate, the threat of introduced predators on all affected breeding islands. Carry out awareness-raising activities on breeding islands to reduce the impacts of human disturbance and introduced mammals.
Text account compilers
Newton, P., Stuart, A., Symes, A., Taylor, J., Ashpole, J, Ekstrom, J., Fjagesund, T., Butchart, S., Hermes, C., Martin, R., Calvert, R., Moreno, R.
Lavers, J., Watanuki , Y., Bourne, W., Uematsu, S., Croxall, J., Sato, M., Sato, K., Takeishi, M., Oka, N.
BirdLife International (2020) Species factsheet: Calonectris leucomelas. Downloaded from http://www.birdlife.org on 24/01/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 24/01/2020.