Archived 2011-2012 topics: Swinhoe’s Storm-petrel (Oceanodroma monorhis): eligible for uplisting?

Initial deadline for comments: 31 January 2012.

BirdLife species factsheet for Swinhoe’s Storm-petrel

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 Chinese 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.

This entry was posted in Archive, Asia, Seabirds and tagged . Bookmark the permalink.

7 Responses to Archived 2011-2012 topics: Swinhoe’s Storm-petrel (Oceanodroma monorhis): eligible for uplisting?

  1. Nial Moores says:

    In the Birds Korea Blueprint 2010, we provide a population range in the ROK of between “less than 30,000 pairs” to 110,000 pairs, with the vast majority of this upper range estimate said to nest on one islet. These estimates are based on the ornithological literature, and were provided with our explicit caveat that colony survey methods are “unavoidably time-consuming and can be prone to high levels of bias, sometimes leading to estimates that are either far too low or far too high” (p. 72-73). It therefore seems highly unlikely that even major changes in population could be detected in the short-term or even medium-term.
    Based on present knowledge, the global population is confined to a small number of sites for breeding; threats have been observed, and documented, at several of these sites (in Japan and in the ROK); and there is a growing body of anecdotal evidence to suggest that some colonies have declined in size, and that threats at some sites are likely to increase. In the absence of improved conservation measures, it seems likely that large declines might occur – and if key nesting sites were affected, this could lead to a very substantial decline in population in a period shorter than three generations. The species should not, at this time, be considered for listing as Vulnerable, but improved knowledge suggests that the population is more susceptible to decline than understood until recently. The main colonies (and therefore the species) already depend on active conservation measures including eradication of invasive alien species and prevention of disturbance.

  2. Praveen J says:

    Recent pelagic trips in SW India (2011) indicate that this species is probably present in fair numbers in autumn in the Arabian Sea.

    July 2011: 1 bird
    Sept 2011: 11 birds
    Oct 2011: 58 birds

    This species was also observed by friends visiting the other side of Arabian sea from UAE ( during the same months.

  3. The Republic of Korea may host more than 100,000 breeding pairs of the Swinhoe’s Storm Petrels in six (or possibly seven) breeding islets, and it may exceed the total breeding pairs of its global population ever known (unpublished data requring futher confirmation).

    It is clear that this species is significantly threatened by invasive plants (and partially invasive animals) in ALL breeding colonies in Korea, and the mass mortality of breeding adults by invasive plants has been also reported. Though this threat seems to be rapidly increasing, nevertheless, there is NO clear evidence of rapid decline of the population, reduced geographic range of occurrence, and so on. According to rough population estimates in one major breeding colony on Chilbaldo, no change was detected since 1980s. Its population size is still quite large as well. Therefore, it is not reasonable to evaluate the Swinhoe’s Storom Petrel as a threatened species using the IUCN Red List criteria at this point.

    However, there may be some pitfalls on this preliminary decision: 1) the recent increase in the extent of invasive plants’ occurrence on all breeding islets (possibly since late 1990s) in Korea will largely increase the adult mortality of the long-living species and it may cause a sudden collapse of a breeding colony. 2) Though there were many short-term case studies, the large number of breeding birds nesting in diverse environments on breeing islets may cause big bias in population estimates due to sampling errors. Thus, we may failed to detect true population trends on breeding islets because there was no long-term and systematic study on the breeding performance due to limited access and logistics. Further information on its breeding status and threats is strongly reqired to understand its conservational status and to manage/protect breeding habitats.

  4. Joe Taylor says:

    The following comment has been received from Dr Masayoshi Takeishi via Mayumi Sato:

    The description about Koyajima and Okinoshima is correct, and I don’t have any more comments to add.

  5. Joe Taylor says:

    The following text has been extracted from the poster abstracts of the First World Seabird Conference Programme:

    Kyung-Gyu Lee

    Impacts of introduced plants on the breeding
    Swinhoe’s Storm Petrels (Oceanodroma
    monorhis) and restoration activities in Korea

    “Impacts of introduced plants on the breeding Swinhoe’s
    Storm Petrels (Oceanodroma monorhis) were studied at
    Chilbaldo, Sokuguldo, Kuguldo, Gaerindo islet of Shinan,
    Korea during the breeding seasons of 2008-2009. Usually,
    Swinhoe’s Storm Petrels make a nest burrow under the cluster
    of Carex boottiana, the dominant vegetation type of the four
    islets. However, invasion of introduced plants, such as
    Achyranthes japonica, Artemisia princes, was detected. In the
    study plots (5m◊5m, n=34 in total), the damage of Chilbaldo
    (13) and Sokuguldo (5) was about 36%, and it was more
    severe than those (about 10%) of Kuguldo (9) and Gaerindo
    (7). Tall and densely occupied introduced plants prevented the
    birds from reaching ground. Moreover dead Swinhoe’s Storm
    Petrels entangled by the utricles of Achyranthes japonica was
    observed at the study areas, except Kuguldo. Especially 386
    dead bodies, including 47 juveniles, were observed at
    Chilbaldo in 2009. When the utricle of Achyranthes japonica
    ripens at fall, its hook-like shape becomes stiff and traps the
    birds. The damage of Achyranthes japonica on Swinhoe’s
    Storm Petrels were reported from 1980s, but current situation
    seems to be more severe than before. In 2008 introduced
    plants were removed in two experimental plots at Chilbaldo,
    and it increased the number of Carex boottiana and the ratio
    of laying burrows. In addition, there were no dead birds in
    three plots where Achyranthes japonica was removed before
    its maturity, but average 2 birds were dead in three control
    plots. Thus, removing introduced plants enhanced habitat
    quality and reduced mortality of the petrels. With the results,
    now we are trying to restore seabird colonies in Shinan.”

    Jong-Gil Park; Chang-Yong Choi; Gyeong-Nam Ko; Gi-
    Chang Bing; Miran Kim; Hee-Young Chae; Gil-Myung Jegal

  6. Joe Taylor says:

    The following text has been extracted from the poster abstracts in the First World Seabird Conference Programme:

    Chang-Yong Choi

    Population viability analysis for Swinhoe’s Storm
    Petrels on Chilbaldo Islet, Korea

    “Approximately 12,000 breeding pairs of Swinhoe’s Storm
    Petrels (Oceanodroma monohris) breed on Chilbaldo Islet,
    Korea. The population was stable for past 20 years, but rapid
    expansion of introduced plants severely threats the breeding
    colony; introduced tall shrubs replace the available nesting
    areas, and Achyranthes japonica entangled and killed storm
    petrels. To identify the effects of each threat, the population
    viability analysis was performed by Vortex 9.98 software
    based on field data in 1987-1988 and in 2008-2009. In 2009,
    we estimated that 424 adults and 59 fledged juveniles killed
    by A. japonica and that the total area of native vegetation
    decreased by 0.3% annually. Because control of introduced
    plants may affect two different ways in harvest and carrying
    capacity, we tested four scenarios: 1) no management, 2) tall
    shrub controls, 3) A. japonica controls, and 4) intensive
    managements for both. When the intensive managements are
    adapted, 21,474±1,190 storm petrels may survive after 100
    years later. Control of tall shrubs also may secure
    14,590±1,443 birds in 2110. However, unless urgent control
    of direct mortality by A. japonica is taken, total population
    will be extirpated within 35.5±4.1 years (scenario 2) and
    33.2±4.0 years (scenario 1). Although many variables were
    rough estimation due to insufficient information on life
    history of this species, this result indicates that control of
    introduced A. japonica is most required on Chilbaldo Island.
    Considering occurrence and rapid expansion of A. japonica in
    all known breeding colonies of the storm petrels in Korea,
    this study suggests that urgent development of action plan and
    its implementation to control A. japonica in breeding colonies
    are essential to long-term survival of Swinhoe’s Storm Petrels
    in Korea.”

    Kyung-Gyu Lee; Jong-Gil Park; Hyun-Young Nam;
    Hee-Young Chae

    • Joe Taylor says:

      The following comments were received from Chang-Yong Choi:

      Please note that this PVA result is too pessimistic. Though we have no further scientific information since then, recent observations suggest that the mortality of adults on the breeding site is highly variable by years (but not constant as high as of 1.8%). Therefore, at this time, I don’t believe the worst case scenario will actually happen.

Comments are closed.