African Wildlife and Environment Issue 64

BIRDING

BIRDING

On average Verreaux’s Eagle pairs breed two out of three years. Predators on Verreaux’s Eagle nestlings are baboons, White-necked Ravens and possibly pythons, leopards and small predatory mammals such as genets. The 2015 Eskom Red Data Book of Birds of South Africa, Lesotho paints a very bleak picture, in that this magnificent eagle is qualified as regionally vulnerable The bird’s primary threat is the stock farmer. Incidents of eagles being caught and killed or maimed in gin traps have been reported. Direct persecution by farmers is usually in retaliation to the eagles catching domestic livestock. Ironically, the beneficial role that a pair of Verreaux’s Eagles play on a farm, in terms of controlling hyrax numbers and distribution, outweighs the cost of an occasional lamb by a factor of 155 times. The depletion of the primary prey species, Rock Hyrax, through hunting is likely to have a negative impact on breeding success. Collisions and electrocutions on powerlines, as well as collisions with wind turbine blades, pose future threats to the species. To conclude, a quote from Jeanne Cowden’s For the Love of an Eagle , copyright 1973. “The sound of the shot froze lizards and hyraxes into gargoyles of terror; and the sudden stillness was so intense that the gale itself seemed to stay in its onslaught. In the late afternoon rain threatened in the ragged clouds as the sun pulled the day over the high towers of the Drakensberg Mountains toward the endless ranges of Lesotho. Only one thing moved. A Black Eagle began to fall from the sky, the spread of its great wings crumpling in grotesque outline. High above, pinned against the void, now alone and suddenly incomplete, its mate watched the crazy plummeting course earthward. A desolate cry tore from it, and the gale caught at the sound, sending it echoing through ravines and crevices until, in rising crescendo, it rang as a challenge to the mountain world. And with the cry, the crier, too, dropped.The great living body planed down with controlled purpose across the mountain’s face. Then abruptly, as though conscious for the first time of danger, it winged over and sped once again to the clouds. There it hung, bewildered, as it quartered each segment of its domain with its fantastic sight. Its gaze came back always to its fallen mate, a black smudge on the mountainside”. under the population-size criterion. Threats highlighted in their findings

it soon replaces it with another one from the unpaired population. They are on the wing at first light and spend their day hunting, soaring, displaying or perching for long periods. Its soaring flight is buoyant and extremely graceful. The Verreaux’s Eagle is extremely prey specific, Rock- and Tree Hyrax being their principle food. Other prey includes a variety of mammals, various birds and occasionally reptiles. Several hunting techniques are applied; they sometimes attack from a perch or with a tremendous swoop from a soaring position, but usually a planned sneak approach is used. Once prey has been spotted, the eagle drops out of view and then suddenly appears in a surprise swoop to make its kill. A pair will hunt co-operatively. The Verreaux’s Eagle rarely calls. One call is a ringing, melodious ‘keee-ooo keee-ooo’, a variant is a loud ‘whaee-whaee’, used when chasing off intruders near the nest. Courtship displays are similar to the territorial displays performed throughout the year and is done singly or by the pair. These spectacular displays include steep, undulating dives, and sometimes somersaults and rolls into the next dive with wings held against the body. Nests are usually built on cliffs or sheer boulder outcrops, some may be on exposed ledges with little shade, and others are placed in small caves where they are sheltered. The nest is usually in an inaccessible position. New nests are flattish structures about 1 m across, but those in long use may grow to large proportions, some 1.5 m across and 2 m and more in height. Nests of 4 m in height are not unusual. Both birds take part in nest building and large sticks are collected on the ground or broken off dead trees in flight. Normally the same site is used year after year. The nest cup is lined with green sprays. Two eggs are normally laid from late April to June, three to four days apart. First-laid eggs are incubated immediately. The female sits overnight and the male shares during the day. The incubation period is normally 44 days. An egg takes about two days to hatch. When the second egg hatches three to four days later, the first chick has already developed its co-ordination, and ‘Cainism’ occurs during which the smaller chick is killed. This apparent biological waste of the second hatchling is an intriguing phenomenon that remains to be convincingly explained. The young eaglet does a lot of wing exercising prior to flying off the nest for the first time between 90 and 98 days. During its first month the juvenile spends much of its time on or near the nest. In its second month it becomes more adventurous, exploring and expanding its range, as well as accompanying its parents for short distances. During the third month out of the nest it wanders further afield. Towards the end of the post nestling period the parents begin to chase it away. By the time it leaves the territory it has not yet killed for itself.

Willie Froneman Birding Expert & Enthusiast willie.froneman@gmail.com

52 | African Wildlife & Environment | 64 (2017)

53 | African Wildlife & Environment | 64 (2017)