Abstract
On May 31st 1986, while observing a pair of Blakiston's Fish Owls (Ketupa blakistoni) in their breeding territory, I witnessed a unique encounter between the male owl and a Black-crowned Night Heron (Nycticorax nycticorax). The Black-crowned Night Heron is very rare in Hokkaido. It does not breed there (WBSJ, 1981), and in fact was not recorded there at all by WBSJ (1982), although OSJ (1974) does mention records from that prefecture. The early summer of 1986 saw an unprecedented invasion of herons and egrets of several species in southeastern Hokkaido (Brazil, in press) and clearly a single night heron arrived during this influx. Since, in Japan, the fish owl is confined to the island of Hokkaido, and now mostly to the eastern third, it is highly unlikely that these two species have encountered each other in this country before. The ranges of the two species do not overlap in the Soviet Union either (Flint et al., 1984).
