The Besra in Hong Kong

This Besra (Accipiter virgatus) was photographed a few weeks ago in a tree it sometimes visits in the morning. The Besra is a forest bird but is known to frequent perches in the open at that time of day. It is widely distributed in southern Asia.

It is only in recent decades that the taxonomy and identification of sparrowhawks has been worked out. In the 1960s the Besra was completely unknown to Hong Kong birders. That is because there were only though to be two species visiting Hong Kong: the Japanese Sparrowhawk (Accipiter gularis) and the Eurasian Sparrowhawk (Accipiter nisus). Both were thought to be passage migrants.  The Japanese Sparrowhawk and the Besra were thought to be geographical variants of the same species. When it was realised that two different species were involved, and it was found that one is actually resident in Hong Kong (Besra) and the other entirely migratory (Japanese) did the position become clear. The Eurasian is still a rare migrant.

Identification of the Besra as a Hong Kong bird, also cleared up our scratching of heads in earlier years, starting in 1966,  as we saw display flights of sparrowhawks above Hong Kong. We could not decide between the two stated to be there at the time. They seemed too big for Japanese and not in the season for migrants of either species. And would migrants be displaying?

The Besra must have become more common as there are more and more trees and bushes compared with the hillsides devastated for decades by the collection of firewood for cooking during the Japanese occupation. The latest field guide has them as ‘fairly common, widespread resident and possibly autumn migrant’ whereas in 2005 it was down as ‘a scarce resident, possibly with increased numbers in autumn’.