An adult drake CANVASBACK photographed in Maryland, USA, showing some paleness on the upper bill (Curtis Brant)
See putative CANVASBACK images here:
http://www.surfbirds.com/cgi-bin/gallery/display.cgi?gallery=gallery9&start=37
For the second year running, this drake CANVASBACK has returned to Suffolk, in East Anglia (Britain). In every sense of the word, this is a typical drake Canvasback but my main reservation is the amount of pale bluish-white half-mooning on the upper surface of the upper mandible. I have always considered this feature to be associated with in-breeding and therefore suggesting that the bird is an escape; obviously in its ancestry, there are Northern Pochard genes.
However, I am keen to hear from birders in North America with experience of wild Canvasbacks. Do you see wild birds with this same feature and if so, what proportion of birds have this feature
Of the 5 or so Canvasbacks I have seen in Europe, four of them have shown some paling on the upper bill, suggesting this may well be a frequent feature. However, on the other hand, it could suggest that the majority of our birds are escapes
I would be very grateful for any comments