Well.
Yes, they can see better at night than hens. So they will stay out until you call them in. I pen mine around the house they are to live in to start with (a few days) and when I put them to bed at night, I call 'ducks, ducks, ducks' and herd them in. Then later, when they are free-ranging, they come to bed when called

Mine spend a lot of time 'fossicking about' in the edges of the beck banks or in muddy patches. They love playing in the beck, washing and chasing about, then they do quite a bit of preening, and then they sleep for ages. They definitely need water, which they can play in and that you can keep clean. Running water is obviously ideal.
I've never had a duck get too fat, so I just feed mine layer pellets ad lib. That said mine are free-range so that might be different if yours aren't. Other people will be able to tell you that better and I've never kept Aylesburys which are a meat bird so might be designed to put on weight a bit more than the Khakis (and my runners and calls).
I give mine sultanas for treats, I throw them on the floor by my feet and there is a 'duck scrum' to get at them
HTH for starters. I think I probably like my ducks the most of all my poultry, they are really funny. Enjoy yours
