This is a very large eagle. The adult is pitch black with a white ‘V’ on its back and white on the rump. The female has solid white on the back and rump, while the male has the white of its back and rump separated by black feathering. The bill is black, the cere and feet are yellow. White ‘windows’ in the wings are a prominent feature of this species. The wings are broad, narrowing towards body. The juvenile is a mottled golden dark brown with black blotches. The nape and crown are golden brown. The immature bird begins to develop white on its back and rump well into the second year of its life.
General Characteristics of Eagles
The word “raptor” comes from the Latin raptare, which means ‘to seize’. Raptors therefore have clasping talons and hooked beaks with which to catch and tear their prey. There are a total of 84 raptor species in South Africa of which 12 are owls and 9 vultures. Some scientists argue that vultures are not really raptors, as their talons are not very powerful and they do not seize their prey in true raptor style, instead eating carrion and relying on their powerful beaks to tear meat and crush small bones.
Depending on conditions, adult eagles may live for 20 to 30 years, and in common with most long-lived animals have very slow breeding rates and an extremely high incidence of mortality among young birds. On average, only 30% of young eagles survive their first year, and only half of these eventually reach maturity. This situation is acceptable provided the adult survival rate remains high. If the balance is disturbed by unnatural mortality factors such as poisoning or shooting, the population may exhibit a drastic decline or even become extinct.
The Black Eagle is limited to mountain ranges and rocky outcrops throughout Africa (from south to north), but young birds may wander widely. The distribution of these birds closely correlates with that of the Rock Hyrax, its favourite prey. Territory size is determined by prey availability and topography.
Black Eagles are monogamous. The nest is built on cliff ledges and may be used for many years. Within the pair’s territory a number of nest sites may be selected, but one being favoured. They are territorial, so will not tolerate other Black Eagles nesting or passing through their territory. Courtship consists of spectacular flights where both birds fall and climb for hundreds of metres. They frequently drop a stick, especially the male, and then stoop and roll onto their backs to catch it.
Feeding & Hunting
Rock Hyrax or dassie make up at least 90% of their preferred prey with the male and female often hunting cooperatively with one bird making it obvious to the prey while the other stoops and veers around rocks to surprise the unsuspecting victim. Black Eagles will also hunt guineafowl, francolin, rock rabbit, scrub hare, mongoose and carrion.
The nest is built by both the male and female and consists of a platform of large sticks. The cup is lined with green leaves. Old nests can be 2.5m in diameter. The nest is almost always on a steep, inaccessible cliff, but very rarely also in a tree. Two plain white or blotched eggs are laid from April to July (mid-winter) and are approximately 66.7-86.0 x 52.0-62.0 mm in size. Incubation is about 45 days and chicks take about 2 days to hatch. Ninety-nine percent of the time only one chick survives due to the “Cain and Abel” struggle where the stronger (usually older) sibling kills the weaker. The surviving youngster will fledge at about 13 weeks. Once hatched, the nestling spends 3 months in the nest before being able to fly and post fledging will remain dependant on the adults for an additional 3 months when it will be forced out of the territory by both adult eagles. The young bird goes through various stages in plumage growth and reaches adulthood over a period of 3 to 5 years.