Colours of Wildlife: Giant Eagle Owl
Created | Updated May 11, 2014
African Giant Eagle Owl
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!"
People seem to like owls, so here is another one for you! This is the (African) Giant Eagle Owl, Bubo lacteus. Its common name is self-explanatory: it is the largest of the eagle owls occurring in sub-Saharan Africa, reaching 3 kg/7 lbs in bodyweight and an overall length of 66 cm/26". (The female is bigger than the male.) It is one of the largest owls in the world, only a few such as the Eurasian Eagle Owl being larger. This species is also known as Verreaux's Eagle Owl, or as the Milky Eagle Owl. The last name refers to its light grey coloration, and is also reflected in its species name, lacteus meaning 'milky'.
It is a species I know well: the first time I saw them in the wild was in the Kruger National Park in 1985, where we found a couple resting in the branches of tall trees growing along a river. They were remarkably well camouflaged amidst the grey of the bark but I was sharp-eyed enough to spot them. They appeared very relaxed. I've seen this species in captivity a lot as well. They often land themselves at raptor rehab centres, and there I was able to get many close-up looks at them.
Pink Eyelids
This eagle owl is one of the easiest to recognize if seen well. Its size, blunt ear tufts, light grey finely barred plumage, dark eyes, and prominent black borders to its white face together are distinctive. But seen close perhaps its most remarkable feature is its eyelids! The upper eyelids are featherless and pink-skinned. This owl also has a habit of letting its eyelids droop halfway over its eyes so that it has an expression of drowsiness, boredom or mild contempt. The actual purpose of the pink eyelids is unknown. It might help with species recognition or signalling between birds but this has not yet been proven. Some owls have been seen with brick-red eyelids; raptor expert Peter Steyn speculates that they might be suffering from sunburn!
Skinner of Hedgehogs
Giant eagle owls are powerful predators. They even catch other large owls and eagles, and one has been seen carrying off a Meller's Mongoose of over 2 kg. At the other end of the spectrum, they often eat insects, particularly the flying termites that constitute one of the great food sources of the savannah. But they are also the only known bird to regularly prey on an item left alone by most other predators: hedgehogs! In South Africa we only have one hedgehog species, which lives in dry, open savannah and bush. Its spines protect it against almost anything – except for the claws and beak of the giant eagle owl. The owls catch the hedgehogs with their powerful feet, the dense scales of which protect them, and with bill and feet together, they actually peel off the spiny skin of the hedgehog, and eat the rest of it. The leftover spiny skin is discarded, usually at a specific dump site a distance away from the owl's perch or nest. It can be distressing to come upon such a site of dumped hedgehog skins, thinking of all the poor critters that fell prey to the owls.
Feigning Injury
An interesting behaviour of breeding giant eagle owls is their feigning displays. These occur in some other birds as well, plovers being well known for it. Eagle owls nest in a variety of sites, often taking over the nests of other large birds like Hamerkops or eagles. They will lay their eggs exposed on the very top of such a nest. When the eggs hatch the owlets (usually two, but the younger of the two invariably dies soon after hatching) try to conceal themselves by lying flat on the nest if they suspect the presence of a potential predator. But the parents – probably the mother, mostly – will try and distract the predator instead. She will do things like flying a distance off and falling to the ground where she will limply flop about as if she were injured. She may even dangle upside down from a branch and then crash into the undergrowth. These bizarre displays are sure to distract most predators who will focus on the female instead while the chicks will lie frozen on the spot on the nest. This behaviour is so ingrained that even if you took the owlet from the nest and put it on the ground right in front of you, it would still try to lie flat and motionless as if that would somehow make it invisible! The owlet is therefore completely docile and doesn't seem to feel any fear or aggression at all. Young owls have been seen going beyond this merely passive display, in actually trying to feign death by lying flat on their bellies with their necks stretched out, heads sagging to the side and their eyes closed.
An Uncommon Owl
Today the giant eagle owl is not very common. It feeds rather voraciously and each owl needs a large hunting territory. But despite occurring at low densities, the owl has a very wide distribution, encompassing all of sub-Saharan Africa apart from the dense rainforests or the open grasslands and deserts. It needs large trees for roosting and nesting. These owls hunt at night but also around dawn and dusk where it will use its excellent eyesight to spot prey. In utter darkness it will, like other owls, mostly rely on its sense of hearing, being able to detect the direction of the slightest rustle caused by a moving critter. Its call is a deep grunting hoot, which resounds through the savannah at night, proclaiming its territory. Mated pairs call to each other in a duet of hoots. They also make bubbling and whistling sounds, and both females and chicks use screeching whistles to beg for food. When food is abundant, breeding can take place each year, but in regions of scarce resources like semi-deserts, breeding may happen only every 2 to 3 years. Chicks fledge at the age of two months but attain sexual maturity only at the age of 3 to 4 years. They may stay with the parents for a year or two before going off on their own. In captivity these owls have lived for 15 years. An adult giant eagle owl is considered an apex predator – at the top of the food chain, fearing no other predator. They are only at risk from ingesting poisonous bait left out by farmers, and from habitat destruction.
