On August 2017, I observed a Northern Goshawk (Accipiter gentilis) wearing an anklet at Mizumoto Park, Tokyo. Thereafter, I observed such a goshawk eleven times until early April 2018. In all records, the observed individual was a juvenile. Characteristics of plumage and the presence of an anklet suggested that all eleven observation records were derived from one or a few individuals, which had escaped from captivity. If the last observed individual was the same as the first one, it had survived for at least 110 days. Currently, by law most goshawks held in captivity cannot be a subspecies breeding in Japan. If exotic subspecies escaping from captivity bred with Japanese subspecies, native subspecies will be at risk of genetic disturbance due to hybridization.
