Mexican duck Id help

[ronbco]

I’m not home in CO at the moment but I have tried to id Mexican Duck a few times on the front range so please excuse the general question about a possible id in AZ.

Would there be any iridescence on the dark mantle of a male Mexican Duck? It was subtle just in the back of the head. Perhaps that is indicative of intergrade?

The other field marks were there though I didn’t look at the tail.

Thanks

Ron Bolton

Berthoud