Passage: The nest is usually a depression in the ground, which may or may not be lined with bits of grass or similar materials. The eggs are mottled and camouflaged. Both sexes share incubation duties. The young hatch after 22–27 days and fledge after 21–24 days. If the parents are disturbed and flush from the nest frequently the incubation period could be extended to as long as 34 days.When hatched, the chicks are downy. Neither altricial nor precocial, the chicks begin to move around and explore their surroundings within one to three days after hatching. Usually they do not stray far from the nest. Chicks are brooded by the adults for the first ten days after hatching. Both parents care for hatchlings. Chick diets always include fish, and parents selectively bring larger prey items to chicks than they eat themselves. Males bring more food than females. Feeding by the parents lasts for roughly a month before being weaned off slowly. After fledging, the juveniles learn to feed themselves, including the difficult method of plunge-diving. They will fly south to winter with the help of their parents.Arctic terns are long-lived birds that spend considerable time raising only a few young, and are thus said to be K-selected. The bird has life span that was thought be around 20 years, however National Geographic, The University of Alberta & Massachusetts Institute of Technology, concluded in 2010 that more than 50% of this species will live past their 30th birthday. A study in the Farne Islands estimated an annual survival rate of 82%.

Question: How many days can the incubation period be extended to if the parents are disturbed from the nest?
34