The female begins incubation when the first egg is laid, unlike most other birds, which delay incubation until the last egg is laid to cause simultaneous hatching. Barn owls lay subsequent eggs every two or three days. Eggs hatch after 21 to 24 days of incubation. However, because the last egg may be laid a week after incubation began, the female may have to incubate for 32 to 34 days before all eggs are hatched. For comparison, chickens incubate their eggs for 21 days and turkeys for 28 days.
Males bring food to incubating females.
This incubation strategy results in siblings occuring in stair-step ages. The first owlet may be 6 to 18 days older than its youngest nest mate. This age difference is visible in the varying size and plumage development of nestlings. Young owls fledge when they are about eight weeks old. Parent owls keep busy feeding themselves and their hungry owlets.