SCIENTISTS say hornbills are a family of birds found in tropical and subtropical Africa, they are characterised by a long, down-curved bill which is frequently brightly coloured and sometimes has a casque on the upper mandible.
Hornbills are the only birds in which the first and second neck vertebrae are fused together, probably providing a more stable platform for carrying the bill.
The family is omnivorous, feeding on fruit and small animals. They are monogamous breeders nesting in natural cavities in trees and sometimes cliffs. A number of species of hornbill are threatened with extinction, mostly insular species with small ranges.
The most distinctive feature of the hornbills is the heavy bill, supported by powerful neck muscles as well as by the fused vertebrae.
The large bill assists in fighting, preening, constructing the nest, and catching prey. A feature unique to the hornbills is the casque, a hollow structure that runs along the upper mandible.
In some species it is barely perceptible and appears to serve no function beyond reinforcing the bill. In other species it is quite large, is reinforced with bone, and has openings between the hollow centres, allowing it to serve as a resonator for calls.
Hornbills possess binocular vision, although, unlike most birds with this type of vision, the bill intrudes on their visual field.
Scientists say this allows them to see their own bill tip and aids in precision handling of food objects with their bill.The eyes are also protected by large eyelashes which act as a sunshade.
Hornbills are diurnal, generally travelling in pairs or small family groups. Larger flocks sometimes form outside the breeding season where the largest assemblies of hornbills form at some roosting sites, where as many as 2,400 individual birds may be found.
Hornbills are omnivorous birds, eating fruit, insects and small animals, they cannot swallow food caught at the tip of the beak as their tongues are too short to manipulate it, so they toss it back to the throat with a jerk of the head.
While both open country and forest species are omnivorous, species that specialise in feeding on fruits are generally found in forests, while the more carnivorous species are found in open country.
Some hornbills defend a fixed territory whereby territoriality is related to diet, and fruit sources that require travelling long distance to reach are often patchily distributed.
Hornbills generally form monogamous pairs. Although some species engage in cooperative breeding, the female lays up to six white eggs in existing holes or crevices, either in trees or rocks.
The cavities are usually natural, but some species may nest in the abandoned nests of woodpeckers and barbets. Nesting sites may be used in consecutive breeding seasons by the same pair.
Scientists say during breeding season and before incubation, the female sometimes assisted by the male begins to close the entrance to the nest cavity with a wall made of mud, droppings and fruit pulp.
When the female is ready to lay her eggs, the entrance is just large enough for her to enter the nest, and after she has done so, the remaining opening is also all but sealed shut. There is only one narrow aperture, big enough for the male to transfer food to the mother and eventually the chicks.
The savannah has many species of these birds but Tanzanian red-billed hornbills found in central Tanzania are small hornbills in the group of the red-billed hornbills. They have curved, bright red bills that end in a small dot of dark orange.
Their sclera can vary from light orange to dark yellow and their pupils are usually dark black. Like most species of hornbills, they support medium-sized circles of black skin around their eyes, both in females and males.
They have greyish-white necks and bellies and their wings, like all red billed hornbills, have large and small spots of white surrounded by black feathers. Their tail feathers are long and black on the exterior and white on the interior.
The trumpeter hornbill is another species of hornbill which is a gregarious bird, usually living in groups of two to five individuals, although sometimes as many as fifty.
Scientists say this hornbill is a locally common resident of the tropical evergreen forests of different parts of Africa south of Sahara.
The African grey hornbill is a member of the hornbill family found in the sub-Saharan Africa. The African grey hornbill is a large bird, although it is one of the smaller hornbills.
Its plumage is grey and brown, with the head, flight feathers and long tail being of a darker shade. There is a white line down each side of the crown and another down the back which is only visible in flight.
The western red-billed hornbill is another species of hornbills that are found in Tanzania, there are five species of red-billed hornbills generally recognised now, but all five were once considered conspecific.
These birds have curved red beaks which are more orange on the lower beak and more bright red on the upper beak, with both ending with a dark orange colour. Their heads are greyish white and have black feathers along the back of their heads and neck.
They have white plumage on their faces and large dark grey eye rings, their sclera is dark brown and their pupils are black.
Their wings are like all red-billed hornbills, with large and small circles of white feathers surrounded by black feathers on the exterior and white on the upper half of the interior and black on the lower half of the interior. They have long tail feathers that are black on the exterior and a greyish white on the interior.
The Abyssinian ground hornbill or northern ground hornbill is another hornbill which is found in Tanzania, this is an African bird, found north of the equator, and is one of two species of ground hornbill. It is the second largest species of African hornbill, only surpassed by the slightly larger southern ground hornbill.
Abyssinian ground hornbill is a large, terrestrial hornbill with black body feathers and white primary feathers which are visible in flight.
The adult male has a patch of bare blue skin around the eye and an inflatable patch of bare skin on the neck and throat which is red, apart from the upper throat which is blue.
The Abyssinian ground hornbill or northern ground hornbill is found in open habitats such as savannah, sub-desert scrub, and rocky areas, preferring short vegetation which enables its visual foraging technique.
The areas inhabited by this species are usually drier areas than the preferred habitat of the Southern ground hornbill. It will tolerate disturbed areas but does require large trees to be used as nest sites.
The Abyssinian ground hornbill lives in open grassland, in pairs or small family parties. They patrol their territory by walking and are reluctant fliers, usually only taking to the air when alarmed.
In captivity, the Abyssinian ground hornbill can live 35 to 40 years, their diet in the wild consists of a wide variety of small vertebrates and invertebrates, including tortoises, lizards, snakes, birds, spiders, beetles, and caterpillars, they also take carrion, some fruits, seeds, and groundnuts.
The Abyssinian ground hornbill prefer to nest in large trees, with baobabs and palm stumps being preferred, the nest is constructed in a cavity. They have also been recorded nesting in other types of cavities including holes in rocks and man-made cavities such as bee-hive logs or baskets.
In other hornbills the nesting female molt their all flight feathers at once but this is not the case in the ground hornbills, the male prepares the nest by lining the cavity with dry leaves before the female enters and lays a clutch of one or two eggs over around five days.
She starts to incubate as soon as the first egg is laid so that the chick which hatches first has a head start in development over its sibling. Incubation of each egg takes between 37 and 41 days.
Scientists say it is during this time when there is no effort to keep the cavity clean and the male is responsible for providing food to the incubating female.
Abyssinian ground hornbills invest a lot in their offspring and the fledged juveniles will remain with their parents for up to three years.
They have a slow breeding rate and an average of one chick is raised to adulthood every 9 years so the adults’ investment in each young bird raised is exceptionally high.
Abyssinian ground hornbills are opportunist feeders, following ungulate herds and forest fires so that they can prey on small animals disturbed by the larger animals or flames. An individual hornbill can walk up to 11 kilometres in a day, pouncing on and eating animals they come across.
They have also been recorded digging for arthropods in the soil and attacking bee hives for honeycomb; they very rarely consume any plant matter as their strong bill is used to capture and overcome the prey before it is eaten.
The southern ground hornbill is one of two species of ground hornbill and is the largest species of hornbill, this is a large bird standing between 90 to 129 centimetres long as females weigh between 2.2 to 4.6 kilogrammes.
The southern ground hornbill is characterised by black coloration and vivid red patches of bare skin on the face and throat which are generally believed to keep dust out of the bird’s eyes while they forage during the dry season.
The white tips of the wings whereby primary feathers are seen in flight are another diagnostic characteristic. The beak is black and straight and presents a casque, more developed in males.
Different researches show female southern ground hornbills are smaller and have violet-blue skin on their throats.
The southern ground hornbill is a vulnerable species, they live in groups of 5 to 10 individuals including adults and juveniles.
They forage on the ground, where they feed on reptiles, frogs, snails, insects and mammals up to the size of hares, meanwhile Southern ground hornbills very rarely drink.
Southern ground hornbill groups are very vocal, their range is limited at its western end by the lack of trees in which to build nests.
Different scientists say while foraging, contact is made by calls in chorus which can usually be heard at distances of up to 3 kilometres.
Southern ground hornbill groups are very vocal and their calls allow each group to maintain its territories, which must be as large as 100 square kilometres even in the best habitat.
The southern ground hornbill is an obligate cooperative breeder, with each breeding pair always assisted by at least two other birds.
It is known via experiments in captivity that birds without six years’ experience as helpers at the nest are unable to breed successfully if they do become breeders.
This suggests that unaided pairs cannot rear young and that helping skill as a juvenile is essential for rearing young as an adult.
In captivity, a maximum lifespan of 70 years is recorded, and it is generally believed that the life expectancy of a bird that survives long enough to fledge is as high as thirty years or more.
Ground hornbills are believed to reach maturity at six to seven years, but very few breed at this age. Nests are almost always deep hollows in very old trees, though there exist reports ground hornbills have on occasions nested on rock faces.
Among Southern ground hornbills, One to three eggs are laid at the beginning of the wet season but siblicide ensures that only one nestling is ever fledged.
Scientists say the period of parental dependence following a 40 to 45 days incubation period and an 85 day fledging period is between one and two years depending on climatic conditions before the young are independent of parents and helpers, which is the longest of any bird.
This means that ground hornbills can normally breed successfully only every third year, breeding is extremely rare in birds probably the only other bird which breeds on a triennial basis is the rainforests.
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