It is difficult to judge size in Doug's photos. In some, the mystery duck looks about the size of nearby Blue-winged Teal (15.5 inches). In others it looks somewhat larger. Relying upon Doug's estimate that it was somewhat larger than a Blue-winged Teal, it still looks significantly closer to 15.5 than to a Gadwall's 20 inches or a Mallard's 23 inches. Unless there is such a thing as a runty Brewer's Duck, I think we can rule out that hybrid.

If the bird is the same size as or larger than a Blue-winged Teal, it is unlikely to be a Green-winged x Common Teal hybrid. Both of those species are smaller than BWTE. (GWTE is 14 inches long, Common Teal about the same).

I don't see any sign that the mystery duck is closely related to a Shoveler or to a Wood Duck. Without some Mallard in him, the green of his head indicates that one of his parents was a Green-winged or a Common Teal. Since the shape of the head's green closely resembles that of a Green-winged or Common Teal, I think one parent almost certainly was one of those two species. The green speculum further supports that speculation. (This is the first time I have speculated using a speculum).

That's as far as I can go with my speculations.

 Bob Fisher
Independence, MO
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