Tuesday 29 December 2009

Japan day 2: Vega and Slaty-backed Gulls

This post shows various age classes of Vega and Slaty-backed Gull. I hope to upload a full sample of birds in the fullness of time, once I am home and can process all my pictures, but for the moment here are some example birds. Images 1-11 are Vega, while 12-15 are Slaty-backed. If you are interested in the field identification of Vega, you might find this article I put on surfbirds a few years ago of some use (http://www.surfbirds.com/ID%20Articles/JapanGulls/index.html); it contains various frequency statistics for wing tip patterns etc.

1. Eye pigmentation varies a lot in Vega; this is a very dark-eyed individual

2. A paler-eyed bird. Most Vegas, like this one, have not yet completed primary moult. This is a little behind the majority, with most birds having full new Primaries 1-9, with the new P10 approx 75% of its full length.

4. Note that the outer primaries are not properly visible as they are regrowing (e.g. P10 is not visible in the far wing)

5. Primary pattern varies a lot in Vega. This is a very typical individual; note the michahellis like P10 and 5 patterns. Some birds have P10 identical to cachinnans, With a long tongue and fully white tip; many also have black on the outer web of P4.

6. 2cy (second winter)? There has been some useful discussion of the age of this bird on Surfbirds Forums (advanced ID). Given the small white tips to the primaries, and the deep white secondary skirt, it may be a 3 cy (third winter). But its general plumage (heavy and extensive head and body blotching, limited grey in the wing coverts and tertials) and bare parts (bill colours, still wholly dark brown eye), are more consistent with a second winter; so if it is a third winter it is very retarded compared to the majoriy of Vega's of this age. I need to look for some other pics of this bird in case I have any flight shots than can resolve this issue properly.
7. 1cy
8. 1cy

9. 1cy
10. 1cy
11. 1cy
12. Slaty-backed Gull, showing off its 'string of pearls'

13. This may not be fully adult; note black on bill and tail.

14. 3 cy
15. 1cy

1 comment:

Tim Sexton said...
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