[ Last edited by richome2 at 16/12/2011 15:35 ] Author: cgeoff Time: 16/12/2011 13:15
I don't believe this is a pure Vega Gull, as primary moult is insufficiently advanced. It can be seen that the outer two primaries, P9-10, are old, while the inner five (P1-5) are full grown. P6 is about three-quarters grown, P7 less than half, while P8 has been dropped but the new feather is not visible. At this time of year, a pure Vega Gull would be well on the way to completing its moult. In Japan, P8 of vegae is full grown a month earlier than this, and some birds would have completed moult entirely by this time.
No, the moult stage of this bird is strongly suggestive of the influence of Heuglin's Gull, which generally completes P8 sometime in December or early January. The leg colour does not seem to be strongly yellow, while the upperparts appear somewhat pale. Together, these features suggest this bird is a hybrid of Vega and Heuglin's.
GeoffC Author: thinfor Time: 16/12/2011 14:45
Thanks for you detailed analysis, Geoff. Author: richome2 Time: 16/12/2011 15:30
隻腳是粉紅色,都有可能是混種 heuglin and vega! Author: brendank Time: 16/12/2011 18:19
I would add that the intergrade zone between Heuglin's and Vega Gull is poorly understood. Many of our Heuglin's might have some amounts of Vega lineage.
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