brendank

26-8-2010 Shing Mun Reservoir

I seem to be seeing lots of Besras suddenly.  It seems to me from photos on the net that on Besra's P4-P6 are about equal length while on Japanese Sparrowhawk--from what I can see on photos on the net--P4 is long, P5 variable (sometimes as long as P4 but sometimes much shorter) and P6 is always short.  This photo shows the equal long primaries for P4-P6.

besra.JPG (194.87 KB)

26/08/2010 22:44

Brendan

HFCheung

Crested Goshawk?  There are six "fingers", or is that the alula?  Also, the "crest" seems to be just visible.

HF Cheung

[ Last edited by HFCheung at 27/08/2010 12:58 ]

ajohn

It looks like a Besra to me.

Brendan, you are correct about the differences in wing shape - Besra has relatively short, rounded wings due to the similarity in length of the primaries. Japanese has a more pointed wing due to having one or two longer primaries.

There are a lot of Besras around at the moment; I saw two at Mai Po yesterday evening. This is typical for late summer, presumably as young birds fledge and leave the nesting location.

brendank

I am not sure whether that is the Alula or not.  I assumed, perhaps wrongly, that it is was P1.  In any event, in the field this bird looked small.  Furthermore, I believe the talons looks quite small and thin and the undertail coverts quite non-distinct.  I don't think that you can see a crest in this picture or any other I took.  I will try to look later to see if any other pics of this bird showed the back of the head more clearly.

Brendan

brendank

I did get one picture of the back of this bird.  I don't see a crest.  But I will let everyone judge for themselves.

Brendan

besra2.JPG (163.23 KB)

28/08/2010 00:14

ajohn

The outer feather on the first photo is, I think, the alula. It is at a different angle from the primaries in the first photo, and on the second photo looks to be overlying the front of the wing (as would be expected of the alula). It would not be visible as a 'finger' in flight (bear in mind that a sunning bird like this may not show the same structure as a flying bird).

For the record, data from birds trapped in HK shows that the longest primary on Besra is usually P4 (occasionally P5). P4 and P5 are always very similar in length (usually 1-2mm difference), P3 is slightly shorter (up to about 10mm shorter). Brendan's photo also fits with this assessment: P4 is the longest, P5 slightly shorter and P3 slightly shorter again. See also: http://orientalbirdimages.org/se ... _ID=&pagesize=1
According to trapping data, Japanese Sparrowhawk invariably has P4 as the longest. P3 and P5 are similar to each other (usually about 5mm shorter than P4), but P3 is usually longer than P5. This leads to a more pointed wing for Japanese. See: http://orientalbirdimages.org/se ... _ID=&pagesize=1
We don't have enough trapping data for Crested Goshawk, but what we do have shows a similar wing structure to Besra. This is supported in the field: Crested Goshawk has a very rounded wing. I find it more noticeably rounded than Besra due to the bulging secondaries, making the wing look 'paddle-shaped'. See: http://orientalbirdimages.org/se ... Family_ID=&p=15

By the way, these are great photos Brendan, very useful for illustrating the differences. I just wish Besras would obligingly perch like this for me. I almost always see them in flight, often just diving into trees.

[ Last edited by ajohn at 28/08/2010 09:08 ]

brendank

Yes, I feel lucky to have two cooperative Besras to photograph in as many weeks.  This is a bird that I have hoping to photograph for a while but only could get quick glimpses of.  Perhaps young birds are less shy than adults.