Buzzards are strongly territorial, and defend their territory throughout the year. They are usually sedentary birds, and movements over 100 km are rare. However, a bird ringed in Aberfoyle turned up in the Breckland region of Norfolk.
The nesting territory contains several alternative nest sites; usually 1-3, but up to 14 have been recorded. A different nest is used in successive years. Distribution of territories depends largely on availability of suitable nest sites. Since much of the foraging is done outside the territory, the territory size is not affected by food availability.
The nest, built by both birds, is usually in a tree, rocky crag or cliff. It is a substantial structure of branches, twigs, heather and other available material. The average size of a newly built nest is 1 m in diameter and 60cm deep. Re-used nests can be 1.5 m across. The shallow cup in the nest is lined with green material immediately prior to egg laying, with further material added gradually until the young fledge.
The female lays a clutch of 2-4 white eggs with red and brown markings, at three-day intervals in mid-April. She does most of the incubation for 33-35 days for each successive egg. The chicks hatch at about two-day intervals.
The female broods the young for the first two weeks, while the male brings the food. Later both parents hunt and provide food for the young. The young fledge when they are 50-55 days old, and stay with their parents for 6-8 weeks after fledging.
The breeding success depends largely on a good food supply and a lack of interference from humans, either illegal or accidental. Human interference causes up to half of nest failures. Three quarters of young buzzards die, mostly from starvation, before they mature at three years old. Those that reach breeding age have an average life span of around eight years. The oldest wild buzzard known was 25 years 4 months old.
The strong maternal instincts of buzzards can be demonstrated by the story of a captive female in the nineteenth century that was said to incubate and rear broods of hen chicks over a period of years.