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