This odd duck caused some confusion at first, but the dust seems to have settled and the consensus is that this is a hybrid between Mallard and Mexican Duck. Mexican Duck has a rather tortured taxonomic history, formerly being classified as a separate species but then lumped with Mallard because of extensive hybridization with Mallard in the northern part of its range. More recently it has been elevated back to full species status despite the apparent hybridization. The rationale as I understand it, is that the amount of hybridization is not significantly different from other Mallard relatives such as American Black Duck and Mottled Duck. To be consistent we need to treat them all the same; either lump them all or treat them all as separate species. In brief this bird is clearly not a pure Mexican Duck because of the black frame at the base of the bill, the dark crown and back, the white in the tail, the black uppertail coverts, the warm ruddy-brown color to the chest, the gray tertials and scapulars, and the more Mallard-like bill. There was some concern that the other parent might be an American Black Duck, but people familiar with those hybrids report that such hybrids are typically much darker than this.
