A dishonest dealer in birds who "makes up" his wares,
either by painting the plumage of live birds
or by fabricating bird skins, affixing false labels, etc.
Hard to believe this happened often enough to warrant its own word.
However, I immediately thought of this video. I give you the best visual reference of a bird-duffer that you will ever see:
Gotta love those Pythons. They set the standard. Best. Ever.