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Range DescriptionThis species is found in the western Pacific, breeding on the coast and on offshore islands of Japan, Russia, and on islands off the coasts of China, North Korea and South Korea. It migrates south during winter, being found off the coasts of Viet Nam, New Guinea, the Philippines and Australia (del Hoyo et al. 1992). The global population has been estimated to number c. 3,000,000 individuals (Brooke 2004). In Japan, where it is thought that the majority of the speciess world population breeds, there are 11 islands that are each thought to be inhabited by more than 10,000 breeding pairs (Oka 2004). A recent survey on the island of Nakanokamishima estimated the population at 5,566 individuals and 2,783 nests (Yamamoto et al. 2015). According to islanders, the species appears to have been declining rapidly on Mikura-jima, but quantitative data are not available (S. Uematsu in litt. 2012). The prevalence of threats from introduced predators suggests that the species is in overall decline; however, further data are required from throughout the speciess range to assess the current population trend.