Do baby ducks sleep with light on or off?

Well I'm takin care of a baby duck my friend found. Older ducks were tryin to drown it. so my friend took it. she had to go somewhere so im ducksitting. I made the duck named lucky go to sleep by turnin the light off. And also pat his head sometimes they like to sleep in human hands. Id he doesn't peep while hes sleeping check on him. Usually they cheep. I hope this works!