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Range DescriptionOceanodroma monorhis breeds on Verkhovsky Island (7,500 pairs), south of Vladivostok, Russia, and Japan (a minimum of 1,000 pairs). There are little-known populations in China, Taiwan (China), North Korea and South Korea, and records suggest that breeding possibly occurs in the North Atlantic. In winter, it migrates south and west to the northern Indian Ocean (Brooke 2004). 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. The species nests at six or seven breeding islets in South Korea (Chang-Yong Choi in litt. 2012). There is apparently anecdotal evidence that some colonies are in decline (N. Moores in litt. 2011).