Coturnix japonica breeds in eastern Asia, including northern Mongolia, Sakhalin Island and the Baikal and Vitim regions of Russia, north-eastern China, Japan, North Korea and South Korea. Some populations in Japan are resident, but most birds migrate south, wintering in southern China, Laos, Vietnam, Cambodia, Myanmar, Bhutan and north-eastern India (del Hoyo et al. 1994). There are also introduced populations in Italy and Hawaii (USA). No reliable population estimate exists, and although the species was previously considered to be fairly common in China (del Hoyo et al. 1994), declines appear to have occurred in Laos (Duckworth 2009) and Japan (Okuyama 2004, H. Nagata in litt. 2009), and there are fears that the species has undergone a significant decline overall (del Hoyo et al. 1994, Duckworth 2009).