3cy american herring gull, NW-Spain

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Stefan
Posts: 65
Joined: Tue Feb 07, 2012 6:28 am

3cy american herring gull, NW-Spain

Post by Stefan » Wed Nov 13, 2019 9:07 pm

This 3cy american herring gull was found by Daniel López Velasco at the fishing fish farm in Lago, Xove in Lugo, Galicia (NW-Spain) on the 23-1-19 and stayed there for about one month. Photos are taken by Daniel López Velasco and David Calleja Marcos. It has several features supporting the identification as being an american herring gull, including pale head, dark-centred tertials, the sharply demarcated bill, scapular feathers of two generations, smooth blotches on the underparts and dark and smooth greater coverts. The barring of the upper tail coverts/rump is quite dense and the tail is quite dark, apart from bit of pale barring on outermost tail feathers (T5 and T6).Surprisingly, some second winter European herring gulls can have surprisingly amount of black in the tail feathers. This individual differs from any of the smith look-alikes I have seen in Iceland. This includes those individuals that have some glaucous gull genes (viking gulls). These tend to have less black in the tail feathes, the outermost secondaries are often not blackish and the upperparts (especially the greater coverts) are rarely so smooth [More comparative work neeed before more affirmative statements can be made]. It is however possible that it has genes from nearctic glaucous gull (i.e. Nelson´s gull). The glaucous gulls found on the E-coast of US tend to be much paler compared with those in Iceland, and thus produce hybrids that differ from those encountered in Iceland. Such pale glaucous gulls, that are sometimes seen in early winter (many glaucous gulls in Iceland become pale in late winter due due to plumage bleaching) are likely to have nearctic origin, including Greenland, but also possibly from Svalbard and Jan Mayen. I have no experience with Nelson´s gull, but one could speculate this could amount for the reduced amount of black in outermost tail feathers.
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