Question: Which parent is sitting on the eggs? What role do the parents play during incubation?
Answer: Incubation does not begin until the third or fourth egg is laid and lasts until the eggs hatch in about 33 days.
The peregrines' typical daily routine during incubation is:
- The female incubates all night.
- At or before dawn her mate goes out hunting. When he returns he calls to her and she leaves the nest to eat. The food exchange usually happens away from the nest. During this period the eggs are unattended.
- Soon after the food exchange the male comes to the nest and incubates the eggs.
- After the female has taken a break, she'll return to the nest and resume incubation. The male will leave.
- At other times during the day the male will offer to incubate the eggs. There is no set time, but at the University of Pittsburgh nest E2 normally relieves Dorothy for a couple of hours in early afternoon.
The amount of incubating the male does depends on the couple's preference. Some males share more incubation duties than others. In the middle of the incubation period, the male is on the eggs 30-50% of the daytime hours. Towards the end of incubation when the eggs are about to hatch, the female spends most of the time on the nest. She wants to be there to assist the chicks as they break out of their shells.
So which parent is on the eggs right now? If it's the middle of the night, it's the female. Otherwise, you'll have to watch closely at "shift change" to see which bird is larger.
(photo from the National Aviary webcam at the University of Pittsburgh)