How do parent procellariiform birds share incubation duties?

Parent procellariiform birds share incubation duties through a system of alternating shifts, ensuring the egg is constantly attended while the other partner forages at sea.1

Once a nest site is established, one member of the pair typically remains on guard to protect the territory while the other feeds to meet the nutritional demands of the developing egg. During the incubation period, mated birds do not feed each other; instead, they take turns incubating for periods of several days at a time.1

This division of labor is essential for their survival: the bird at the nest fasts and loses weight, while the bird at sea feeds and builds up fat reserves. This cycle allows the parents to manage the long incubation periods required by these species, which can range from 40 days in the smallest petrels to approximately 80 days in the wandering albatross.1