Just promoting your guide business is all.
You think I made that up on how to tell the drakes apart? Even 40+ years ago the duck id hand books mentioned the primary differences. And since you do not believe me, then go argue with Cornell Ornithology Lab.
https://www.allaboutbirds.org/guide/greater_scaup/id "head with greenish iridescence."
https://www.allaboutbirds.org/guide/Lesser_Scaup/id "head with purplish iridescence"
I'm pretty surprised neither of you knew this as I've considered both of you veteran hunters and not at all wet behind the ears. That being said, it then makes me wonder what % of the hunters have no idea how to ID in hand a lesser form a greater ...