A male duck will try ti mate with anything remotely poultry, lol, or so i've heard. It will be able to mate with your 2 lb chicken, but as for your 10lbers, he probably won't be able to because the chickens won't let him. lol. A drake will most likely want to be around your chickens because ducks are flock animals. He might go wander off on his own every now and then, but will probably stay near the chickens. While a duck will probably mate with a chicken, the ability to produce offspring from such a crazy mix is astronomical. I have heard of the possibility of a half duck half goose, but geese and ducks are much more closely related, and even then, I've only heard about it, never seen it.
If you really want ducks, I recommend getting just a few females for eggs and enjoyment, or get two-three females and a male. Then you can have baby ducks... And I'm pretty sure it's been voted that baby duckies are the cutest of baby water fowl, lol.
