Yes, and they will generally get along most happily. At certain times of the year they might or might not scrap a bit, but you can see that happen with any birds; I have several pens of bachelor drakes who do quite well together. I even have ones that have been in breeding pens with females and they get along well with other males when put back into bachelor pens as long as they don't have females to fight over. Calls are very social and will often sleep together in little piles to stay cozy. I only have one pen that gets riled up, but they only get that way when I let a bunch of ducks out free around their pen, and understandably so: they want out too! Three boys, especially if they have been raised together, will likely do fine; always expect an initial pecking-order sorting out if they don't.