I think they go on little spurts of sleep, and then they have to make sure that everything is okay in the dark. I wonder if it happen to wild ducks, since you would think it would alert predators. I hear off and on my ducks inside their duck cage in the closet at night, and I imagine within any group of ducks that something like this is happening:
-zzzzzz *wake* oh, oh, HEY, I'M NOT ALONE AM I?
-NO, YOU'RE NOT ALONE, WAIT, AM I ALONE TOO?
-NO, YOU'RE NOT ALONE, I'M HERE TOO
-I'M HERE TOO, AND GOSH YOU GUYS I REALLY CAN'T TELL YOU HOW HAPPY TO SEE I'M NOT ALONE EITHER
-HEY IS THAT YOU, HOW YA DOIN, ITS BEEN WHAT, LIKE TWO HOURS? I'M HERE TOO, AIN'T THAT SOMETHING
-OH HEY YOU, YEAH, IT'S BEEN A WHILE, I'M GLAD TO SEE YOU'RE STILL HERE, BECAUSE I'M HERE TOO
-OK THEN, WELL IF WE'RE ALL HERE then I guess I'll just ....
[all] zzzzzzzzz