Since I have dogs and a cat we mix their dog food with the cat food and my duck always eats their food. It's dry food and the bits are pretty small, I was really worried about her eating it but I read on a thread here that it's actually good for them (the cat food since it has more protein)
I know of a duck that suffocated because dry dog kibble got stuck in his throat. That's the worst case, and only once have I heard of that happening. But I wanted to share that knowledge so you'll know to be careful.
The cat kibble is small enough.
And I don't give any duck any food without water.