Black Duck (American Black Duck) Anas rubipres
In its normal range of North America this species is under threat through hybrisation with introduced Mallards. It occurs in Europe only as a rare vagrant, and some individuals may show evidence of hybridisation with Mallard. In addition some vagrant Black Ducks have bred with local Mallards to produce hybrids this side of the Atlantic.
The following bird was paired to a Mallard. It seems to be regarded as a pure bird, but the dark behind the eye showed a hint of green at some angles and the tertials seem a little on the pale side, so I am not entirely convinced it is 100% pure. Not an F1 hybrid anyway, so presumably originating from North America either way.
Black Duck (with Mallard), Strontian (Highland, UK), 15th March 2014