At Happy Island we saw many Sparrowhawks – both Eurasian and Japanese – allowing a good comparison of these similar species. The best indicator was structure with Japanese being smaller-headed, shorter-tailed and generally more compact. If seen well, plumage details, including the more strongly barred breast and underwing, with the streaking often reaching the vent, helped to distinguish Japanese from the more familiar Eurasian.
On our first day, I felt sorry for the migrant passerines. Not only were they dropping into the woods, exhausted, but the woods were full of Sparrowhawks. Every call or squeak from a passerine resulted in at least one but often two or three Sparrowhawks homing in on the noise like guided missiles. Surprisingly, we found one Japanese Sparrowhawk suspended high in a tree, obviously the victim of a collision with a branch, something one doesn’t expect from these highly maneuverable raptors.