I own two muscovy ducks (male and female) until last they bought sleep together. They are young adult though haven't begin laying. Last night my drake when to bed alone and his babe kept hunting insect all night but they were back together this morning.
This sounds like normal duck behavior to me, ducks don't sleep at night like chickens when they roost until morning? Ducks can sleep with one eye open as the other half of their brain is at rest. 
