Initial deadline for comments: 31 January 2012.
Swinhoe’s Storm-petrel Oceanodroma monorhis is a localised breeder on islands and coastlines in north-eastern Asia, specifically Japan, Russia, North Korea, South Korea, China and Taiwan, ranging widely to the territorial waters of countries in South-east Asia, South Asia, the Middle East and East Africa when not breeding. The species is listed as Least Concern on the basis that it was not thought to approach the thresholds for Vulnerable under any of the IUCN criteria.
This species has a very large non-breeding range, but a restricted breeding range that was not thought to approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence of less than 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). The population trend appeared to be stable, and hence the species was not thought to approach the thresholds for Vulnerable under the population trend criterion (at least a 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 (fewer than 10,000 mature individuals with a continuing decline estimated to be at least 10% over ten years or three generations, or with a specified population structure).
A recently published study, however, has improved our knowledge of this species’s status, including the threats it faces. Sato et al. (2010) describe threats at breeding sites as including mining operations, introduced predators and tourism. On Koyashima, Fukuoka (Japan), the breeding colony was decimated by accidentally introduced brown rats Rattus norvegicus (Takeishi 1987 in Sato et al. 2010) and has not fully recovered despite predominantly successful eradication efforts (Sato et al. 2010, Takeishi per M. Sato in litt. 2011). The island of Okinoshima, only 1 km away, is inhabited by both black rats R. rattus and brown rats and is likely to be a source for the accidental introduction of rats to Koyashima in the future (M. Takeishi per M. Sato in litt. 2011). On Chilbaldo, South Korea, the species has been severely impacted by introduced plants, such as Mugwort Artemisia vulgaris and Achyranthes japonica, that, if tall and dense, prevent birds from entering their burrows (Lee 2010). In addition, Achyranthes japonica acts like a mass of hooks when the plants mature in September, and hundreds of O. monorhis perish when they fly into the plants and become trapped. Although work has been undertaken in the past to remove introduced plants from parts of the island, the problem posed by Achyranthes japonica now appears to be getting worse (Lee 2010).
Some colonies in Japan are threatened or potentially threatened by the activities of recreational visitors in warm seasons (Sato et al. 2010 and references therein). Disturbance from tourists visiting Gageo Island, South Korea, is increasingly likely to impact birds nesting on the nearby Gugeul Islets (Birds Korea 2010). Furthermore, Bentenjima Islet, Shiriyazaki (Japan), has been connected to the mainland to facilitate the mining of limestone, and breeding there is thought to have ceased (Sato et al. 2010). Intense fishing operations near the species’s breeding sites probably result in occasional landing by fishermen, increasing the risk of rats being introduced to other breeding colonies. In addition to anthropogenic threats, rocky islands with shallow soil that are inhabited by the species, such as the Kutsujima Islands, could suffer severe erosion during a typhoon or other heavy rainfall event, which would probably seriously affect colonies. Competition for nesting sites from species such as Streaked Shearwater Calonectris leucomelas, could negatively impact O. monorhis. Predation by gulls is another potential threat (Sato et al. 2010). Sato et al. (2010) also estimate the world population at a minimum of 130,000 pairs, confirming that the species has a very large population. However, Birds Korea (2010) state that c.100,000 pairs nest on Gugeul Islet, implying that possibly over 75% of the global population breed on one very small island. On the basis of a high proportion of the total population breeding there, combined with the threats associated with this location (primarily human disturbance), Birds Korea (2010) propose that the species be uplisted to Near Threatened.
Further information is sought on the likely population trend in this species. A rate of population decline approaching 30% (typically 20-29%) over the last three, or projected over the next three, generations would probably make the species eligible for listing as Near Threatened under criterion A. A decline of at least 30% over the same time period would likely qualify the species for Vulnerable. BirdLife estimates the generation length for this species to be c.14.6 years, giving a trend period of c.44 years.
Birds Korea (2010) Swinhoe’s Storm Petrel Oceanodroma monorhis. The Birds Korea Blueprint 2010 for the conservation of the avian biodiversity of the South Korean part of the Yellow Sea. Busan, South Korea: Birds Korea.
Lee K.-G. (2010) The status of seabirds on Sasu and Chilbal islands, and the management of invasive species. The Birds Korea Blueprint 2010 for the conservation of the avian biodiversity of the South Korean part of the Yellow Sea. Busan, South Korea: Birds Korea.
Sato, F., Karino, K., Oshiro, A., Sugawa, H. and Hirai, M. (2010) Breeding of Swinhoe’s Storm-petrel Oceanodroma monorhis in the Kutsujima Islands, Kyoto, Japan. Marine Ornithology 38: 133-136.