An interesting variation in a male Eurasian Wigeon Anas penelope L., 1758 at Slimbridge, Gloucestershire
Paul F. Whitehead
Moor Leys, Little Comberton, Pershore, Worcestershire, WR10 3EH. Email: firstname.lastname@example.org
During a visit to the Wildfowl and Wetlands Trust Slimbridge Reserve in Gloucestershire (VC34 SO70) on 19 January 2015 enormous numbers of dabbling ducks were active especially on Tack Piece grazing marsh. Amongst them was a single male Eurasian Wigeon Anas penelope which differed from all others in having a clear wide metallic green flash on either side of the head rather like that of male Teal Anas crecca L., 1758. The bird watchers that I pointed this out to agreed that they had seen nothing like it before and the possibility was that it had acquired some Teal genetic material in the past.
I discussed the matter with experts at WWT Slimbridge including Mr Martin McGill, the Senior Reserve Warden, who kindly informed me that a small percentage of Eurasian Wigeon that winter at Slimbridge are known to show this feature the significance of which is unknown (on the day the frequency would seem to have been less than 0.2% of all wigeon). Both Mr McGill and Mr David Paynter, the WWT Slimbridge Reserve Manager, felt that the feature did not result from hybridisation or certainly not recent hybridisation; I agree with this. However, it may well raise questions about the evolution of the group.
As far as I can see from a limited quick scan this striking variation is not depicted in the literature. The World Wide Web reveals images of similar but not nearly such well-marked birds, two of them from North America, at http://www.raywilsonbirdphotography.co.uk/Galleries/Birds/non-passerines/Anatidae/Wigeon.html and https://vancouverislandnature.wordpress.com/2013/02/. The image shown at http://vanwaglajam.deviantart.com/art/Wigeon-Stroll-503084425 includes some speculative observation.