Okay, so I'm once again looking into ducks. Right now I feed my chickens starter/grower feed with oyster shell on the side, and it's worked great. Can I feed ducks the same thing? I plan on keeping them in a pen next to the chicken pen to start and then letting them free range with my chickens. I plan on getting around four ducks and I've got two large dog houses so can they use those as small coops? And will they come when called if trained? Thanks!