Penguins form monogamous pairs for a breeding season, though the rate the same pair recouples varies drastically. Most penguins lay two eggs in a clutch, although the two largest species, the emperor and the king penguins, lay only one.[54] With the exception of the emperor penguin, where the male does it all, all penguins share the incubation duties.[55] These incubation shifts can last days and even weeks as one member of the pair feeds at sea.