Where we used to live there was a small farm pond about a block away. One year a mated pair of mallards flew over the bird feeder in our yard and landed for a look. My mother threw out two slices of bread to them, and after conferring between themselves they ate the bread. The male let the female go first, and she ate the center parts; then the male ate the crusts. They flew back in the direction of the pond..Every day about the same time they would land about 200 feet away from our house, waddle up to the back door, and quack until we threw them two slices of bread. They had the same routine for about two weeks and then didn’t return anymore..We knew married human couples that weren’t as polite as those ducks were to each other.