Usually red kites first breed when they are two years old, although exceptionally they can successfully breed when they are only one year old. They are monogamous and the pair-bond in populations is probably maintained during the winter, particularly when the pair remain on their breeding territory. For migrant populations the fidelity to a particular nesting site means that the pair-bond is likely to be renewed each breeding season. The nest is normally placed in a fork of a large hardwood tree at a height of between above the ground. A pair will sometimes use a nest from the previous year and can occasionally occupy an old nest of the common buzzard. The nest is built by both sexes. The male brings dead twigs in length which are placed by the female. The nest is lined with grass and sometimes also with sheep's wool. Unlike the black kite, no greenery is added to the nest. Both sexes continue to add material to the nest during the incubation and nestling periods. Nests vary greatly in size and can become large when the same nest is occupied for several seasons.