In some areas birds form an important part of the diet, including guineafowl, francolins, bustards, and poultry. Birds as large as a European Stork are recorded to have fallen prey to the Martial Eagle. In other areas the diet is largely mammalian, especially hyrax and small antelopes.
Animals as large as an Impala calf are taken, and some monkeys, also occasionally young domestic goats, and lambs. Carnivores like mongoose are sometimes taken, even occasionally Serval Cat and Jackal; also a few snakes and large lizards. It will evidently eat whatever is available, with a preference for game-birds, hyrax, and poultry. It is not known to eat carrion at all except possibly dead lambs.
Nests are built invariably in trees, at any height from 20 to 80 feet above ground, but often in the largest tree in the area, growing on a steep hillside or in a gorge, where the bird has a clear sweep off the nest. Pairs have one or two nests, which are used in alternate years if more than one, but for successive breeding attempts if only one.
They are huge structures about four to six feet across and up to four feet thick, and often basin-shaped when new - much broader than they are deep. They are made of large sticks up to one-and-a-half inches in diameter, lined with green leaves. They may be used by a succession of birds for many years.
The Martial Eagle breeding season may thus begin in various parts of the range in a wet season, the early dry season, or late in the dry season, and some part of the cycle must extend through rainy periods. Incubation is normally by the female, but a male has been known to sit. The female leaves the nest to feed and is not usually fed by the male at the nest. The incubation period is probably about 45 days. The young is very weak and feeble when first hatched, but becomes more active after about twenty days.
At 32 days feathers show through the down, and completely cover the bird at 70 days. The young Martial Eagle is fed by its parent till it is about 60 days old, and well feathered, when it starts to tear up its prey itself. During the early fledging period the female remains near or on the nest, and the male hunts and brings prey.
The female remains in the area and receives prey from the male for about 50 days. After that she hunts or brings prey to the nest herself and the male seldom appears. The young one is closely brooded in its first few days, but after fourteen days the female does not brood it except at night.
The young bird, after making its first flight (at about 100 days), may return to roost in the nest for some days, and thereafter moves away from it. It remains loosely attached to the nest site for some time, and may be seen not far from it for up to six months.
The largest eagle in Africa, this is a bird of the uninhabited stretches of thornbush and savannah found over much of Africa, occurring also in open plains and semi-desert country. Martial Eagles spend on average 85% of their time perched and take to the wing predominantly in the late morning (10am). This behaviour drops off sharply from around 3pm and is largely driven by thermal availability. Martials are thus also predominantly opportunistic perch and ambush hunters.
Martial Eagles will soar for hours on updraughts without hunting, and with a full crop, but it does most of its hunting from the soar also, killing or attacking by a long slanting stoop at great speed, or a gentle descent into an opening in the bush, the speed of the descent being controlled by the angle at which the wings are held above the back. It may kill from a perch, but does so seldom, and most of its kills are surprised in the open by the speed of the eagle's attack from a distance.
A pair of Martial Eagles may have a home range of anything up to 50 square miles, and they wander about over most of it. They often hunt for several days in one area and then move on to another, since complaints of kills are often voiced for several days in succession in the same area. It is much shier than the other big eagles of Africa, and generally keeps away from man.
Although not migratory in the strict sense it makes local movements involving flights of several hundred miles, and a pair may not habitually be found near their breeding locality. It is by habit a hunter of game-birds and small mammals out in the open, but also preys upon man's domestic animals, though it certainly kills much less than it is often accused of killing. Probably on balance it is a beneficial bird to man.