Colours of Wildlife: Martial Eagle
Created | Updated Jul 1, 2012
Martial Eagle
Willem is a wildlife artist based in South Africa. He says "My aim is simply to express the beauty and wonder that is in Nature, and to heighten people's appreciation of plants, animals and the wilderness. Not everything I paint is African! Though I've never been there, I'm also fascinated by Asia and I've done paintings of Asian rhinos and birds as well. I may in future do some of European, Australian and American species too. I'm fascinated by wild things from all over the world! I mainly paint in watercolours ... but actually many media including 'digital' paintings with the computer!"
This is a painting of a Martial Eagle, Polemaetus bellicosus. The scientific name is in Greek and Latin, and means 'war–like war eagle'. It is the only species in its genus; most other large eagles reside in the genus Aquila (Latin for Eagle). In Afrikaans it is called 'Breëkoparend' or 'Broad–headed Eagle', because of its broad, rather flattened head. The martial eagle is the largest eagle species in Africa, and one of the largest in the world. (Some of the Eurasian Sea Eagles, and the South American Harpy Eagle, are bigger.) It reaches an overall length (bill to tail) of 90 cm/3 ft, and a bodyweight of 6 kg/13 lbs. Its wingspan can reach 8.5 feet/260 cm. In this species, as in the Gabar Goshawk that I wrote about previously, the females are bigger than the males.
From its name you probably can deduce that this eagle means business. It is one of the fiercest predatory birds in the world, and occasionally kills antelopes (specifically, duikers – I hope to paint and write something about them soon) that are six times its own weight! It will rarely attack full–grown antelopes, but lambs are fair game. In South Africa it has been recorded taking young (not to mention occasional adults) of the Common, Red and Blue Duikers, Impala, Springbok, Oribi and Grysbok. It also takes young baboons, warthogs, jackals, and adult hyraxes, hares, squirrels, monkeys, mongooses and rodents. It will occasionally prey on farm animals: poultry, piglets, sheep and goat lambs. For this reason it is often persecuted by humans. But these are never a significant component of its diet. Martial eagles also hunt reptiles, including the largest of snakes, and lizards, especially the large and tough monitor lizards. They will catch birds up to the size of adult storks, or young ostriches, but they mostly hunt medium–sized ground birds like guineafowl, francolins (a kind of partridge) and bustards. Lastly, they will even eat carrion if it is available.
This eagle, with its huge wings, is an expert at soaring. This is an amazingly energy–efficient mode of getting around. Eagles have an uncanny ability of knowing just where updrafts are, however much these may vary depending on the day and the weather, and will use minimal energy to travel from one to the next, merely allowing the air movements to waft them higher and higher, traversing huge expanses of the countryside while hardly beating a wing. Martial eagles often reach altitudes at which they are invisible to human eyes from the ground … in fact, if you follow them as they spiral upwards on the thermals over the hot African savannah, they will eventually be beyond the resolving ability of powerful binoculars as well. Yet, from that height they can nevertheless still spot their prey, even if it's something as small as a hare! They have some of the keenest eyes of any raptor species … indeed, this means they have perhaps the sharpest vision of any living thing. Their broad, flat heads are made to assist them with this: their 'eyebrows' project sideways over their eyes to shade them from the intense, tropical sun. They do most of their hunting by spotting prey from the air.
When a promising item is spotted, the eagle will swoop down on it. This is not done in the steep, ultra fast dive that the Peregrine Falcon uses … instead, it is typically a slower, shallower swoop, started from as much as 6 km/4 miles away from its intended prey. If the environment is not open enough, it will use a more vertical approach, attacking from above and dropping down using its wings like a parachute. It hits its target feet first, and strikes with its long and immensely powerful talons. Its momentum magnifies the effect of its strength and weight, and many times the force of the collision is enough to kill its prey instantly. It can kill antelopes by grabbing them around the neck and strangling them. Like falcons, it will occasionally catch other birds in mid–flight, surprising them with a fast stoop from above. It will sometimes steal food items from other large raptors as well.
Sometimes this eagle will also hover in place over a patch of ground, lightly trilling its wings, seeming to defy gravity. In such cases it will still be making uses of breezes and updrafts to help it stay in place. Lastly it will hunt from perches high up in trees as well. My eagle is shown perched in the typical attitude: straight, upright, broad–shouldered, alert and attentive, in almost military posture.
Despite its militant name and nature this is a very vulnerable eagle species. It needs huge swathes of territory for hunting: in the entire Kruger National Park, over 20 000 square kilometers/4 000 square miles, there are only about a hundred breeding pairs. Also, it is a slow and erratic breeder. It needs tall trees to nest in, but has been recorded breeding in a pothole in a cliff, and some nest on power pylons. They often nest around valleys where there will be air movements and updrafts to get them started on the soaring, but will use flat land as well. The nest is usually in the fork of a tree, 6 to 15 m/20 to 50 ft above the ground. It is made of sturdy sticks, and pairs keep adding to it, year after year, until it is huge, over 2 m/almost 7 ft deep and wide. There is a shallow central depression which the pair lines with leaves, in which they lay their eggs, or more accurately, egg. (This is therefore not one of those eagles that lay twoeggs, with the first–hatching chick then killing the younger, weaker one.) The female does most of the incubation duty, but the male does help out. He brings food to her as well. The female on the nest will lie down flat and try to make herself inconspicuous, so as to minimize chances of predators spotting the activity at the nest and deducing that it contains a yummy egg or chick. The incubation period seems to be about forty–five to fifty days.
The female will brood the chick or stand over it to shade it from the sun. The male will bring food for them both. He will very considerately and painstakingly pluck all bird prey items. When the eaglet is seven weeks old, the female will start leaving it alone to hunt for herself, and for the chick – she now becomes its main provider. The chick is able to fly at around 90 to 110 days, but its parents may continue to feed it for another three to eight months, while it learns to hunt for itself. On average a pair of eagles will successfully raise one chick every two years. It takes the young eagle six to seven years before it attains full adult plumage, going through a number of different molts. Typically a sub–adult martial eagle will be grey above, with white edges to the feathers, and white without spotting below. Its size and crest distinguish it from the youngsters of other eagle species.
Although the Martial Eagle is very widely distributed in sub–Saharan Africa, occurring everywhere except in the dense rainforests, it is a threatened species. It is very thinly scattered over its range, because of heavy persecution by humans, as well as habitat destruction, particularly the cutting down of trees large enough to nest in. They are also at risk from man–made environmental factors: some collide with power lines and are electrocuted, while others drown when trying to drink from steep–sided reservoirs. There are still some, but not many, in the large nature reserves and national parks. But outside these areas the species is in serious need of protection, which mainly comes down to educational initiatives among the farming community. Eagles may rarely catch livestock, but they also catch animals that prey on crops, and the presence of large eagles indicates healthy environments and ecologies.
