Status and Conservation of the Japanese Murrelet (Synthliboramphus wumizusume) in the Izu Islands, Japan

Abstract

We collated available evidence of breeding and conservation problems for the Japanese Murrelet in the Izu Islands, Japan. After species description in 1835, it was first collected in the Izu Islands in 1877, with breeding first noted in 1901. Over the 20th century, murrelets were found breeding at 11 islands (i. e., Udonejima, Niijima, Shikinejima, Hanshima, Kozushima, Onbasejima, Tadanaejima, Sanbondake, Motone, Kojine, and Torishima) and were not thought to breed at 7 islands (i. e., Oshima, Toshima, Jinaijima, Miyakejima, Mikurajima, Hachijojima, and Hachijokojima). Surveys have not been conducted at 7 islands (i. e., Zenisu, Inanbajima, Aogashima, Beyoneizu-Retsugan, Myojinsho, Sumisujima, and Sofugan). The population is centered in the northern Izu Islands between Udonejima and Sanbondake. Once considered the world stronghold for the species, a large population decline apparently occurred in the mid-late 20th century: a) breeding no longer occurs at Shikinejima and Kozushima; b) some breeding habitat has been lost at Sanbondake; c) large numbers of nests reported by egg harvesters at Udonejima, Hanshima, and Sanbondake in early century no longer occur; and d) murrelets were observed less frequently on ferry trips between Oshima and Niijima in 1990-95 than in 1983-89. Current breeding population size appears to range between 350-850 breeding pairs (-7-43% of the global population estimated between 4, 000-10, 000 birds or 2, 000-5, 000 pairs). Major colonies occur at Tadanaejima (100-300 pairs), Onbasejima (75-150 pairs), and Sanbondake (75-100 pairs), plus 20-30 pairs at Kojine. Another 100-300 pairs may nest at other islands (i. e., Udonejima, Niijima, Hanshima, and Torishima) where recent estimates are not available. Conservation issues include: human settlement; past egg harvesting; recreational surf fishing at remote islands; predation by introduced predators; habitat loss due to post-war bombing of Sanbondake; habitat destruction due to human activities; habitat loss due to volcanic eruptions; relatively high levels of predation by crows, snakes, and falcons; and mortality in commercial gill nets. Additional surveys, monitoring, and assessment of conservation issues are urgently needed in Izu Islands for this rarest species of the family Alcidae which is endemic to Japan.