Large feral shelduck?

Large feral shelduck?

Observation - Large feral shelduck?. Description: Large (50% bigger than mallard) duck. Chestnut body, yellow legs, blue-grey bill with black tip, irridescent (blue/green) black wings and head. Seemed imprinted on a mallard drake. No knobs on bill (c/f scoter). On stream, at Fife coast

Large (50% bigger than mallard) duck. Chestnut body, yellow legs, blue-grey bill with black tip, irridescent (blue/green) black wings and head. Seemed imprinted on a mallard drake. No knobs on bill (c/f scoter). On stream, at Fife coast