Colours of Wildlife - Monteiro's Hornbill
Created | Updated Aug 4, 2013
Monteiro's Hornbill
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!"
Hornbills count among my favourite of all the birds, and I've already featured the Southern Yellowbilled Hornbill, the Sulawesi Wrinkled Hornbill, the Malabar Pied Hornbill and the Southern Ground Hornbill. But the more the merrier – I wouldn't mind painting them all! Monteiro's Hornbill, Tockus monteiri, is a species I haven't seen yet. It occurs in Namibia, a country I've only visited once, and it lives in the northern parts while I've only been in the south. This hornbill is the most arid-adapted of the hornbill species. Most of them live in rainforests, but this species lives in sparsely-wooded, rocky semi-desert. In some parts of its range the average yearly rainfall is less than 100 mm/4". Apart from Namibia it also occurs in southwestern Angola.
Monteiro's hornbill is generally similar to other small African hornbills like the Yellowbilled and Redbilled hornbills. It also has a resemblance to the Crowned Hornbills, which are forest species, and the Bradfield's Hornbill, which lives in dry but still well-developed woodland. It reaches a length of about 55 cm/22", and a weight of about 350 grams/12.5 oz. For its size it has quite a formidable bill, which, being dark red, is its most conspicuous visual attribute. The male has a slightly larger bill than the female.
This hornbill's call also most resembles those of the Yellowbilled and Redbilled hornbills. It is a repeated series of clucks, hoarser and lower than those of the aforementioned species. Its territorial call starts with single notes, 'kok-kok-kok-' which then turns into double-notes, 'kokkok-kokkok-kokkok' with an increase in volume and pitch as well.
Ground Feeders
The small African hornbills include a number of species that, unlike most other hornbills, have become adapted to feeding partly on the ground, of which this species is a good example. They are not nearly as terrestrial as the ground hornbills, though. They still have very short legs and small feet. But they will often be feeding down below the trees, in the grass or on open patches of rocky or sandy soil, taking short hops, catching insects in their stout but dexterous bills. They will also pick up fallen fruits, pods and flowers, or snip off new, tender shoots forming after good spring rains. They will use their bills to dig in the soil, excavating trenches up to 30 cm/12" long and 5 cm/2" deep in search of subterranean bulbs. But they do not feed only on the ground: they will hunt insects in the bushes and trees as well, sometimes raiding wasp's nests. After each day's foraging they will roost in trees or on rocky ledges.
In these arid regions rains are unpredictable. These hornbills therefore are not always bound to strictly defined territories. In dry times they will form flocks of up to 50 birds that will wander around in search of good foraging areas. But during the rainy season they will pair up to map out and defend their territory. The pair will give their territorial call together, lowering their heads and bobbing their body up and down with each 'kok' or 'kokkok'.
Nesting and Breeding in the Desert
This species' dry habitat affects its breeding. The small hornbills (all those other than the ground hornbills) all have the system of 'imprisoning' the female while she breeds. The other hornbills pick a large hole in a tree, the entrance of which they seal up with mud and/or dung. But because this species lives in such arid land, large trees are rare and thus it frequently cannot find any suitable tree holes. Therefore it very often chooses a crack or hole in a cliff or rock face. Also, such holes often don't have neat, round openings.
Thus the Monteiro's hornbill often has a much more extensive job of plastering it up to leave only a small slit for the female's bill to poke through so the male can feed her.
The male is the one who seeks out suitable nest sites. It searches its territory and first plugs up the openings of suitable rock or tree cavities with mud so that other birds or animals can't use them. Then it will show these to the female, and she will pick the one she considers to be the best. The sealing is done with mud, taken from rivercourses that in the rain season will contain a trickle of water. Monteiro's hornbills also incorporate mashed-up millipedes in their nest walls and linings! These invertebrates exude a poisonous juice and this might help control bacteria, fungi and nest parasites. The female will seal herself up and then wait for three to fifteen days before starting to lay eggs, perhaps to make sure the site is a safe one. The cavity is lined with grass, leaves, pods and bark. The clutch size depends on how much rain falls during the season: in good seasons she may lay as many as eight eggs, in dry seasons as few as two. The eggs are laid at intervals of two to four days so that the chicks vary in ages. Because she cannot mate once sealed up she has to store her mate's sperm and keep it viable for as long as 21 days, taking into consideration her pre-egg-laying test time in the hole as well as the time she takes until she lays the last egg.
While incubating the eggs in her little 'prison' the female hornbill moults her feathers. She first sheds her wing and tail feathers. Thus, her period of flightlessness coincides with her being safely shut in. She also sheds some of her body feathers. All these feathers contribute to the nest lining so when the chicks hatch – which have naked skins – they have a nice fluffy nest to keep them warm. Not to mention their mother!
During all this time the male hornbill is very busy catching food not just for himself but for his female and her chicks as well. At two separate periods he will make a point of bringing snail shells to her: first when she's about to lay her eggs – to ensure enough calcium to form thick, strong shells for them; and second, before she exits the nest, to make sure she has enough calcium to strengthen her bones after the long period of inactivity. The female breaks out when the chicks are about 20-25 days old. She with the male's help re-seals the nest and now they both feed the still-growing chicks, until they are able to fly and fend for themselves. They break out then. But the nesting hole is often re-used again for the next and following breeding seasons.
Because of the female's extreme dependence on the male during her period of incarceration, these hornbills are amongst the most strictly monogamous of all bird species. The slightest sign of cheating by the female will lead to the male no longer being as interested in caring for her and her chicks. This forces the male to be faithful as well – he simply will not be able to find other females willing to risk their and their chicks' livelihoods for the sake of a fling!
Because of the aridity of this hornbills habitat, food is hard to come by, and even with the male doing his best it often happens that chicks starve to death after hatching. This usually happens to the youngest and smallest of the chicks. On average, only about a third of all eggs laid ultimately lead to fully fledged chicks.
So far Monteiro's Hornbill is fairly common in its restricted range. Its habitat is dry and rugged and not many humans share it. But in some areas of its distribution humans raise cattle and goats and this can result in overgrazing and reduced vegetation and food. But this hornbill benefits greatly from nest boxes – this is one way in which humans can help this interesting species. Not only that, but by erecting nest boxes that could be inspected easily with minimum disturbance to the birds inside, ornithologists have managed to learn a great deal about the breeding habits of this species and, by extension, hornbill breeding in general.
