Japanese Murrelet Synthliboramphus wumizusume Scientific name definitions

24–26 cm; 139–213 g (1 Gaston, A. J., and I. L. Jones (1998). The Auks. Oxford University Press, Oxford, UK and New York, USA. Close ). Short, thick, pale bluish-grey bill with dark culmen; iris dark brown, almost blackish; black head with crest of long, narrow black feathers, and with white stripes on sides from top of eye meeting on nape; blackish and bluish-grey upperparts ; white throat and underparts, with greyish-black flanks ; yellowish-grey legs and feet. Distinguished from S. antiquus by crest, more prominent white on crown-sides, lack of black on lower throat and by slightly larger bill (2 Brazil, M. (2009). Field Guide to the Birds of East Asia: Eastern China, Taiwan, Korea, Japan and Eastern Russia. Christopher Helm, London, UK. Close ). In winter, lacks crest  and head stripes; more closely resembles <em>S. antiquus</em> , but separable by having overall paler head  with dark cap less extensive, and often retains at least indication of white crown-sides (2 Brazil, M. (2009). Field Guide to the Birds of East Asia: Eastern China, Taiwan, Korea, Japan and Eastern Russia. Christopher Helm, London, UK. Close ). Juvenile as winter adult, but head and upperparts appear browner.

Coasts and islands off E & S Japan (mainly from S Honshu and Izu Is S to Shikoku and Kyushu) and S Korea; possible breeding in Russia (Peter the Great Bay). Winters mostly offshore from breeding locations.

Offshore and along sea coasts in boreo-cool subtropical waters of NW Pacific. Breeds on small rocky islets and sea coasts. Forages mainly offshore, to edge of continental shelf, also inshore where upwellings or converging currents concentrate food near surface. Winters offshore, mostly in temperate, cool subtropical waters.

Winters mainly offshore, mostly close to breeding areas. General post-breeding dispersal normally within warm currents flowing NE off E coast (Kuroshio Current) and W coast (Tsushima Current) of Kyushu and Honshu; birds reported N to S Sakhalin and Kuril Is and S to Taiwan, but speculated that largest numbers might winter at sea SE of Hokkaido, at the confluence of the Oyashio and Kuroshio Currents (3 Piatt, J.F. and Gould, P.J. (1994). Postbreeding dispersal and drift-net mortality of endangered Japanese Murrelets. Auk. 111: 953-961. Close ). Most return to vicinity of colonies by mid to late Feb, reoccupying nesting sites shortly thereafter. Movements between post-breeding exodus and spring return comprise short distances. Winter distribution poorly known, but probably determined by relative abundance of small fish and planktonic crustaceans. Two out of three murrelets tracked during the non-breeding season using light-level geolocators stayed in winter in SW part of Sea of Japan, while the third moved S into the Pacific Ocean (4 Yamaguchi, N.M., Iida, T., Nakamura, Y., Okabe, H., Oue, K., Yamamoto, T. and Higuchi, H. (2016). Seasonal movements of Japanese Murrelets revealed by geolocators. Ornithological Science. 15(1): 47–54. Close ).

Mostly planktonic crustaceans, especially euphausiids, and small larval fish throughout year. Summer foods probably similar to those of S. antiquus in Sea of Japan and S Sea of Okhotsk, mainly crangonid shrimps (Sabinea, Sclerocrangon) and Pacific herring (Clupea harengus), Pacific saury (Hypoptychus dybowskii), sandeels (Ammodytes), smelt (Osmerus) and sculpin (Triglops). Winter diet unknown, probably largely euphausiids. Feeds mainly over continental shelf, usually in small groups, with diving times and depths as for S. antiquus.

Two calls described, a "byubyubuy" nocturnally at colonies, and a bunting-like "chi chi chi chi", uttered abruptly (2 Brazil, M. (2009). Field Guide to the Birds of East Asia: Eastern China, Taiwan, Korea, Japan and Eastern Russia. Christopher Helm, London, UK. Close ).

Phenology and reproductive biology poorly known. Spring arrival mid to late Feb; laying normally mid Mar to late Jun or early Jul, and fledging mostly by late Apr to end of May. Probably monogamous, with high mate and site fidelity. Colonial, in small and localized groups owing to small population size. Nocturnal at colony. Nests primarily in rock crevices and cavities and under boulders, but also excavates short burrows in soil and under roots of trees and tussock grasses, sometimes in debris and stone walls; may use existing burrow of other species. Two eggs, pale tan or buff (sometimes bluish), size 51·8–56 mm × 33·5–35·5 mm (1 Gaston, A. J., and I. L. Jones (1998). The Auks. Oxford University Press, Oxford, UK and New York, USA. Close ), sometimes one, laid at night, laying interval probably 7–8 days; incubation period unknown, probably c. 32–33 days, by both sexes for periods of 24–72 hours; hatching synchronous, within a few hours; downy chick brownish grey above, white below (differs from that of S. antiquus in having a dark cap contrasting with white cheeks and throat, whereas S. antiquus has dark cheeks with some white behind the eye) (5 Kim, D.-W., Kang, C.-W., Kim, H.-J., Kwon, Y.-S. and Park, J.-Y. (2012). Breeding of the Japanese Murrelet Synthliboramphus wumizusume in South Korea. Forktail. 28: 151-153. Close ), precocial, unfed until leaving at night with parents for sea, c. 1–2 days after hatching, when family immediately swims offshore, often travelling non-stop for 10–20 hours; parents guard and feed young until fully grown, probably at least one month later. Breeding success relatively low, c. 38% of eggs laid produce chicks that go to sea. Most losses at egg stage, occasionally young chicks, usually taken by introduced predators e.g. rats (Rattus) and other small rodents when left unattended. Survival rates and age of first breeding unknown; probably as for S. antiquus.

VULNERABLE. Rarest and most threatened alcid, and probably second-most threatened seabird species in N Hemisphere. Population small and still declining, estimated by BirdLife International at c. 2500–10,000 mature individuals (1995), restricted to five small areas off SE Japan: Izu Is, with c. 1670+ birds at eight sites; Honshu, with 200+ at Mimiana I and small numbers at Kutsujima and Nanatsujima in Sea of Japan; Shikoku, with small numbers on Koshima I; Kyushu, with 3000 at Biro I, 60 at Eboshi I, and 30 at Okinoshima Is; and Danjo Is, with small numbers at two sites. A new estimate in 2015 amounted to 2,600–4,700 pairs BirdLife International . Other breeding sites may exist: juveniles recently sighted outside breeding season in Seto Inland Sea, >150 km from nearest known breeding site (6 Iida, T. (2008). The first confirmation of the non-breeding habitat of Japanese Murrelets Synthliboramphus wumizusume. Ornithological Science. 7(2): 163–165. Close ), with several family parties also seen SW of Yashima Island in W Seto Inland Sea (7 Iida, T. (2010). [The first confirmation of several family parties of Japanese Murrelet Synthliboramphus wumizusume in the western part of the Seto Inland Sea.] Japanese Journal of Ornithology. 59(1): 73–75. In Japanese. Close ), and two adults and two downy chicks off Tateyama City, at S end of Boso Peninsula, 70 km from nearest known breeding islands. Minute population of perhaps <10 pairs reported in South Korea (on Daegugul I, Dong I and Jeju I) (5 Kim, D.-W., Kang, C.-W., Kim, H.-J., Kwon, Y.-S. and Park, J.-Y. (2012). Breeding of the Japanese Murrelet Synthliboramphus wumizusume in South Korea. Forktail. 28: 151-153. Close ); may also nest in very small numbers (under 100 birds) in Peter the Great Bay, Russia, but fledglings and adults collected at sea in region may have migrated there from Japanese colonies. Small population concentrated at only a few locations during and outside breeding season makes species highly vulnerable to disturbance from human activities. Historically, believed to be more widespread and numerous, but human exploitation for food, habitat destruction and alteration, and introduction of alien predators to breeding colonies have undoubtedly caused extirpation of many island populations. In Izu archipelago, once considered the stronghold of the species, current total is under 2000 birds, with breeding on only three of ten islands that had active populations in early 1950s. Rats and feral cats continue to be the major threat, but species also features in bycatch of Korean squid fishery operating in sea area thought to be important for S. wumizusume in winter (3 Piatt, J.F. and Gould, P.J. (1994). Postbreeding dispersal and drift-net mortality of endangered Japanese Murrelets. Auk. 111: 953-961. Close ). Immediate conservation need for species' survival is protection of existing breeding sites by: regulation and control of human activity; initiation of programme to eradicate all alien predators at active and former colonies; establishment of control measures to prevent spread of alien predators to predator-free islands; and a comprehensive survey and monitoring programme to determine present distribution and numbers, assess population trends, and identify factors responsible for changes observed. Highest priority must be given to this conservation goal by national and international agencies responsible for protection and management of marine birds and their ­habitats.