My Hen Carrie has 8 chicks that are 3 weeks old today. None of the eggs were from her. She takes care of them wonderfully. I do not think they know the difference.
Just please be careful when you mix ducks and geese with chickens, turkeys and gamebirds. I had a friend who hatched out turkeys with a duck and some of them followed "mom" into the water and actually drowned before she could separate them.