Habitat, breeding and nesting habits
Eagles are monogamous and they pair for life, although if one of the pair dies, the survivor will readily accept a new mate.
Adults occupy a hunting and nesting area known as a ‘home range’ all year. Birds can be seen soaring and advertising their 'ownership' of a site at any time, but their spectacular undulating display flight is most often seen from February to May.
Each home range contains several night-time roosts and often a choice of two or three alternative nest sites, called eyries, usually on cliff ledges. Both adults build the nest, which is a substantial structure of branches, twigs and heather, lined with woodrush and grass, and decorated with green foliage.
The eyries are traditional and can be used for many years by the same or successive birds. The eyrie is added to each year it is used, and can end up quite a remarkable size. Cliff nests are 1-1.5m across and up to 2m high, while tree nests can be twice this size. The largest known British nest, discovered in Scotland in 1954, was 4.6m deep and had been used for 45 years.
The female generally lays two eggs 3-4 days apart in March, and incubates them for 43-45 days. Incubation starts with the first egg, and the chicks hatch a few days apart. The first chick to hatch is dominant over the younger one, which has only a 20 per cent chance of surviving the crucial first weeks.
The female does most of the brooding and feeding of the young, while the male provides the female and the young with all the food, especially in the early stages. She broods the chicks almost continuously for the first two weeks. After this, she will regularly leave the nest and share the hunting with the male.
The young will fledge when they are 65-70 days old, and will become independent after a further 90-100 days. Juveniles occasionally stay with their parents until November or December but are usually driven away by October. The young birds will breed for the first time at 3-4 years of age, when they can expect a lifespan of around 14 years. It is thought that 75 per cent of young birds die before reaching maturity. The oldest known golden eagle was more than 32 years old.