When you pick them up by the neck and they are taller than you, you shot a swan.
The swan's look like 747's flying. Slower wing beat, smaller groups typically, large bodies. Snows have smaller bodies, necks and black wing tips. Go and do some research on line or hit one of the areas that holds them and watch their flight patterns, how they behave and take some lessons in the field on them. To many guys shoot at swans in the field thinking they are snow geese. If your not sure, don't shoot it.
I can't say I have seen any Peking ducks flying around unless someone slipped a Chinese menu under your vehicle wiper blade and it blew out. If by chance you do get a white duck, it's probably more likely a domestic, moorage, park or pen raised released to wild duck. Versus the leucistic bird that everyone always shoots. Maybe common, but not as common as one may think. Some guys probably have some domestic ducks on there walls. I could be wrong though.
