查看完整版本: Besra or Crested Goshawk?

Besra or Crested Goshawk?

This accipiter landed almost right over me yesterday 21-8-10 at Tung Ping Chau.  Initially thought it was quite small so was thinking Besra.  However, then thought based on iris color that it was more likely a Crested Goshawk.  But then it seems that in photos many Besras have yellow irides.  Didn't really see this bird in flight clearly. Any thoughts from the photo?

[attach]6949[/attach]

Brendan

Hello Brendan,

I'm going for Japanese Sparrowhawk: from what I've seen of Crested Goshawks, they show thicker talons, a longer bill, and bulkier build than in this bird. Besra juveniles tend to have thicker stripes on the abdomen, while young Japanese Sparrowhawks tend to show round spots on the belly as in this bird. Also Besra doesn't seem to migrate much, but Japanese Sparrowhawks certainly do - and thus turn up on offshore islands more frequently I guess.

In any case, it's still very exciting to have an accipiter to land right on top of your head 3551873d93aa445  !!

Interesting!  From what I can see in photos and there aren't too many good ones--the gular stripe on Japanese Sparrowhawks appears less distinct than Besra or Crested Goshawk.  This birds seems to have a have a quite pronounced gular stripe.

Also, from what I can see for the Avifauna of Hong Kong, Japanese Sparrowhawks seem to start showing up in October.  There does not appear to be any summer records of this species so it would be interesting if this bird could be IDed as a Japanese Sparrowhawk.

I think this bird is a juvenile Besra. It seems to be relatively small and slim, which does not favour Crested Goshawk. I also think the bird is too heavily marked below for a juvenile Crested Gos, which usually seem rather pale and spotted.
I find structure to be the best way to separate Besra and Japanese. Japanese usually appear longer-winged and shorter-tailed, compared to Besra which has rounded wings. The wing on this bird appears to be fairly rounded - the longest primary appears to be P5 (i.e. the 5th feather, counted from the outer wing). This favours Besra over Japanese, which should have the wing point at the 4th primary, notably longer than the other feathers. I am not sure about plumage differences between the two, but I think that the plumage fits OK for juvenile Besra. Also, of course, date does not favour Japanese which has never previously been recorded in summer.

In terms of location, I think the suggestion that Japanese is more likely on offshore islands is misleading. All the HK accipiters have turned up on Po Toi and other offshore islands, and Besra seems to be at least partly migratory through HK (with peak numbers during passage). I would think that Tung Ping Chau provides suitable breeding habitat for both Besra and Created Goshawk, and either should be possible there.