I have two Mallards (drake and hen) that live in the chicken coop. They have been in there since they were 6 weeks old and they are now 4months old. We built them a nest in the corner of the coop and they slept there every night. Recently, they have learned they can fly and get themselves more than 5 inches off the ground. The past week, I go in to lock the coop up, and the ducks are sleeping in the chicken's nesting box. The boxes are about 2ft off the ground and the ducks get in the middle box together. I don't know if this is normal, or if something is getting in there and freaking them out on the floor. I really believe they think they are chickens, they act more like them than they do real ducks. They also have a strange attachment to our rooster, and the nesting box they sleep in is directly below where he sleeps.