Justification of Red List Category
This species has a small population which is thought to be declining rapidly as a result of disturbance at breeding sites, predation and mortality from drift-net fisheries. It is therefore listed as Vulnerable.
By 2015, 38 colonies (current and historical) were reported, with a total estimated population of 2,600-4,700 pairs (Otsuki and Nakamura 2016), equating to around 5,200-9,400 mature individuals. National population sizes have been estimated at <100 breeding pairs and c.50-1,000 individuals on migration in Korea and c.100-10,000 breeding pairs and c.50-1,000 wintering individuals in Japan (Brazil 2009).
Populations are thought to be declining rapidly through the combined impact of bycatch mortality and predation by invasive species.
Synthliboramphus wumizusume is endemic to the warm current regions near central and southern Japan, where it breeds on uninhabited islands (BirdLife International 2001). The most important breeding sites are in Kyushu, notably the islands of Biro-Jima, Koya-Shima and Eboshi-Jima, and the Izu Islands, notably Onbase-Jima and Onohara-Jima. Breeding has also been recorded on Gugul Island and Jeju Island off the southern coast of South Korea, is suspected at Dok Island in the East Sea/Sea of Japan (Kim et al. 2012), and it may also breed in Peter the Great Bay, Primorye, Russia. After breeding, birds move northwards along Japan’s Pacific coast towards Hokkaido, and recent tracking of three individuals found that two birds travelled along the coasts of the Japanese archipelago in an anticlockwise direction during the course of a year, whereas the third bird moved up and down the Pacific coasts of Japan’s main islands (Yamaguchi et al. 2016). Early winter movements include southwestward along the coast of Primorskii, the People’s Democratic Republic of Korea and the Republic of Korea, or southwestward along the Pacific Coast of Honshu and Shikoku. Birds have been found to winter in the southwestern part of the Sea of Japan, or move southward into the Pacific Ocean (Yamaguchi et al. 2016), with some apparently moving south to the Nansei Shoto Islands. The species is still declining in many localities, particularly the Izu Islands (Carter et al. 2002).
It frequents rocky islets and headlands during the breeding season (between mid-February and early May), nesting in single pairs, small groups and sometimes in large colonies. In the non-breeding season, it occurs offshore, occasionally entering bays. Juveniles have been sighted outside the breeding season in the Seto Inland Sea, an area previously thought unsuitable for Japanese Murrelet, at least 150 km from the nearest known breeding site (Iida 2008). This was confirmed by the sighting of several family parties around the south-west of Yashima Island in the western Seto Inland Sea (Iida 2010). Two adults and two chicks with down, seen close to the coast of Tateyama City at the south end of Boso peninsula, point to other unknown breeding locations, as these sightings were 70 km from the nearest known breeding islands (Fujita 2008). Breeding is suspected on Dok Island in the East Sea (Sea of Japan) from a dead chick recorded on Seo Island in 2005 and an adult with two fledglings filmed in 2009. More recent records confirm a further breeding location in southern South Korea based of a downy chick photographed on the south coast of Jeju Island, and one adult and two juveniles seen and photographed at sea between Gapa and Mara Islands offshore from Jeju Island (Kim et al. 2012).
In the past, high levels of harvesting of both eggs and adults likely contributed to substantial population decline. Egg harvesting at Biro-Jima likely occurred through most of the 20th century until about 1993, but particularly heavy harvesting occurred in 1940–1960s, during and after World War II. The estimated number of eggs harvested in the 1940s to 1960s period was 1,100–2,080 eggs per year. In total, an estimated 47,740– 111,880 eggs were harvested in the 81-year period between 1912 and 1992 (Otsuki 2013). A rough conservative estimate of the number of adults harvested in 1944–1959 is 180–320 adults per year, and 3,056–5,450 adults were estimated to have been killed over a 27-year period between 1944–1970. By about 1970, harvesting of adults appeared to have been discontinued (Otsuki 2013).
At present, the species suffers from interaction with commercial fisheries. The estimated total mortality of the species in high-seas drift-net fisheries represents a significant proportion of the total world population (Piatt and Gould 1994). At least 98 Japanese Murrelets were killed in 1990 and between 40-160 individuals may have been killed in 1991. The estimated annual mortality of adults in drift nets (24-250) would equal 1-10.4% of the breeding population. Cessation of gill-net fisheries in international waters in 1992 may have reduced the impact from past levels, but a 320 km Exclusive Economic Zone of Japan still remains operational (Piatt and Gould 1994).
The species is known to be vulnerable to predation by rats Rattus spp. (Piatt and Gould 1994, Croxall et al. 2012). In 1987, the remains of 145 individuals were found on Koya Island, where the birds had apparently been killed by rats (Takeishi 1987, Ono 1993). The estimated total mortality was 414 birds. Brown rat Rattus norvegicus has been introduced to some nesting colonies and almost extirpated the population on Koya-Jima, before rats were been eradicated in 1987/1988. However, rats were reintroduced in 2006, and then possibly eradicated for a second time. Landings by fishermen pose a continuing threat of rat reintroduction (M. Sato in litt.). The species is also susceptible to cat Felis catus predation, and is exposed to cats at some colonies. Marado, South Korea, is a popular tourist attraction, and a breeding ground for c.400 Japanese Murrelets, accompanied by c.40 cats. It is believed that cats kill at least 30 birds per annum on Marado (S. Chan pers. comm. 2015). However, the presence of other predators on the island has been confirmed, so mortality might not be caused by cats alone (K. Otsuki pers comm. 2015).
Previously, oil spills have occurred within the species's range. The Nakhodka oil spill in 1997 is one of the largest tanker spill accidents on the Japanese coast, releasing almost 6200 kl of oil in the coastal area of Mikuni (Toyoda and Inagaki 2000). The level of regular exposure to oil at sea likely makes the threat ongoing, but only to a minority of the population at a particular time. No rapid population impacts resulting from oil spills have been recorded as yet.
Conservation Actions Underway
CMS Appendix I. It is legally protected in Japan. Several breeding colonies are protected as National Wildlife Protection Areas, including Nanatsu-Jima, Kiinagashima, Okino-Jima, Danjo-Gunto, Biro-Jima, Tadanae Island, Ohnohara-Jima and Kanmuri-Jima (K. Ono in litt. 2012). Gugul Islet (South Korea) has been designated as a Natural Monument. In Japan, educational materials have been produced to inform fishers about the species and about the importance of the largest known breeding colony on Biro-Jima Island, and research on nest predation is ongoing.
Conservation Actions Proposed
Conduct coordinated surveys of breeding sites to determine current population size and trends. Improve understanding of movements during the non-breeding season. Establish new protected areas at important colonies that are not officially protected. Restrict human access to islands with breeding colonies. Control predators at breeding colonies and establish artificial nest boxes. Research and design methods to reduce the bycatch of seabirds by fisheries.
26 cm. Small alcid. Short, thick, pale bluish-grey bill. Black head with black crest (summer only) and white stripes on sides of head from top of eyes, meeting on nape. Blackish and bluish-grey upperparts. White throat and underparts. Greyish-black flanks. Yellowish-grey legs and feet. Juvenile has browner upperparts. Similar spp. Ancient Murrelet S. antiquus lacks crest and has black on throat.
Text account compilers
Moreno, R., Mulligan, B., Taylor, J., Benstead, P., Fjagesund, T., Anderson, O., Gilroy, J., Khwaja, N., Martin, R., Miller, E., Calvert, R.
Sato, M., Otsuki , K., Ono, K., Chan, S.
BirdLife International (2020) Species factsheet: Synthliboramphus wumizusume. Downloaded from http://www.birdlife.org on 14/08/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 14/08/2020.