Colours of Wildlife: Gabar Goshawk

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Gabar Goshawk

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 watercolour painting of a Gabar Goshawk, Micronisus gabar, sometimes placed in the same genus as the larger Chanting Goshawks, Melierax. The name 'Micronisus' is derived from 'mikros' (='small' in Greek) and 'Nisos', a Greek king who had magical powers that vanished when his daughter Scylla cut off a lock of his hair, much like Samson of the Bible. The gods then changed him into a hawk. The 'gabar' part is not so clear, but it might be based on a word in the language of the Khoi people. 'Melierax', its alternative genus, means 'song–hawk'. In Afrikaans it is known as a 'kleinsingvalk', or 'little singing hawk'.

I have seen this species only a few times so far. Nevertheless, it is not a rare species, and very widely distributed over the savannah regions of Africa, only absent from rainforest, true desert or treeless grassland. It also occurs in the south of the Arabian peninsula.

This is a small bird of prey, the size of a pigeon, with an overall length of about 30 cm/12". But it is a doughty hunter, mostly catching small birds. In this, and in overall appearance, it resembles the sparrowhawks of the genus Accipiter, to the point of being hard to distinguish from them in the field. But in its relationships it seems to be closer to the Melierax goshawks. These are much larger birds that hunt in open country and mostly catch prey on the ground. The similarity between this species and the sparrowhawks is therefore an example of convergent evolution: when species that are not very closely related come to resemble one another due to having adapted similar lifestyles.

Another interesting feature of the Gabar goshawk is that it comes in two different colour schemes. The one I illustrated is the typical, with a grey body and white–and–grey barred lower chest and abdomen, white barring in the tail and wing feathers, and a white rump. The rarer form is the melanistic, or black phase, where the body is uniformly blackish but still with white barring in the wing and tail. Both morphs have red legs and a red cere (the fleshy covering of the base of the bill and nostril region). The black form is more frequent in dry regions, and can comprise from a twentieth to a quarter of the individuals of any population.

Then there's an interesting feature that this goshawk shares with many other birds–of–prey, but especially the species that hunt birds: the females are significantly larger than the males. Why this is so is still being debated. It has been found that some sparrowhawks have a natural 'division of labour' between the sexes: the males hunt different–sized birds from the females. Other reasons may be that the female uses her greater size to protect her against unwanted attentions from males during the breeding season, or to defend her nest and chicks against predators. But none of these explanations are entirely satisfactory in the absence of clear evidence. This is yet another mystery of nature that we should research more.

The hunting method of this little raptor combines features of the chanting goshawks and the sparrowhawks. It frequently chooses a perch from which it spies out the environment, but this perch is usually not high and open, but rather a less conspicuous perch inside the canopy of a tree or bush. It will then, when it spots potential prey, fly out, and will most of the time pursue its targets on the wing. These are typically small birds like weavers, barbets, pipits or starlings, but occasionally as large as a francolin (a kind of partridge). The male and the female usually stay close to each other, but do not hunt cooperatively.

But sometimes this goshawk will be more active in its hunting method, flying rapidly from tree to tree or bush to bush, intending to flush out its prey, then chasing it down. It is very fast and agile. Pursuit flights lasting as long as a minute and a half, or as far as a hundred yards (90 m), have been recorded. Another method it employs is nest robbing, whether of open nests, or enclosed one like the densely woven nests of weavers. It sometimes tears a hole in the roof of the nest, other times hangs upside down and pushes its head or even a foot into the nest opening (which is at the bottom of the weaver nests) and tries to grab a chick. In typical weaver colonies, many of the nests are empty, 'dummies', mostly because female weavers will have their mates build several practice nests before finally settling on one to lay her eggs in. Therefore gabar goshawks will usually spend some time watching the weaver colony from a distance, checking out the activity of the weavers to determine which nests contain chicks.

Non–bird prey items have also been recorded: mice and other small mammals, lizards, and even small snakes. They will catch insects as well. They have even been seen chasing down prey on foot on the ground – sometimes chases starting in trees end up here.

When the breeding season starts, the male begins to call while sitting on his perch to attract females. The call is a high–pitched, repetitive 'ki–ki–ki–ki'. When a female shows up, additional courtship behaviours follow: they will chase each others in flight through the trees, and the male will also offer food to the female. If they finally decide they are right for each other, they'll build a nest. This is typically in a tall tree. Unlike many other raptors, this species does not seem fond of alien tree species like Eucalypts and Pine trees that have been widely planted in South Africa, sticking to the native thorn trees.

A very interesting nesting habit of this species is that it incorporates living spiders and their webs in its own nest! The basic nest is built from twigs, and then lined with smaller twigs and spiderwebs. Living spiders come along with the bits of spiderweb that the goshawk gathers, and when planted on the nest surface, simply continue building it so that eventually the whole goshawk nest is covered in cobwebs. Yet again we still don't know what the point of this is. It might be to camouflage the goshawk nest as nothing more than a big spider colony, or maybe the spiders keep away other insect pests from the chicks.

When the nest is ready, the eggs are laid. This happens in Spring or early Summer. The clutch ranges from two to four eggs. They are laid in intervals of a couple of days, and the chicks also hatch at these intervals. The male and female share incubation duties, and the eggs hatch after a bit more than a month. This is at least a raptor species where the siblings don't try to kill each other (as they do in many large eagle species) so more than one chick can be raised to adulthood each year. They are fully feathered at the age of four weeks, but the parents still feed them for a while longer.

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