Hornbills – Natural histories of extraordinary species that changed our world

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Hornbills – Natural histories of extraordinary species that changed our world

Myths and Ornaments

At first glance Tring seems an unlikely place to find hidden treasure. But the former private museum of Walter, Baron Rothschild, in this small Hertfordshire town, is full of surprises. Along with one of the finest collections of stuffed mammals, reptiles and insects in the UK, it is also home to the bird collection of the Natural History Museum, its darkened rooms full of avian treasures. Skins and specimens of now extinct species such as the great auk and dodo are stored next to those of the familiar birds we take for granted, along with tray after tray of eggs, collected from all over the world. But of all these remarkable specimens, one stands out: an object so unusual it takes a moment to realise what it is.

It is the skull of a helmeted hornbill, a bird native to the Malay Peninsula, Sumatra and Borneo in South East Asia. But this is no ordinary skull, for its rich, buffy-orange front is covered with intricate and beautiful carvings, done in such detail you need a magnifying glass to appreciate their beauty. It depicts a band of Chinese warriors in a town alongside a river, with a man holding a flag showing a Chinese character that means ‘literature’ or ‘culture’. As Jo Cooper, Senior Curator of the avian anatomical collections, notes, there is also a tiny kingfisher caught at the very moment when it dives into the waters.

Technically speaking, the carving is not actually on the skull itself, but on the ‘casque’: a large plate on the bird’s forehead, which it uses in fights with rivals. Other hornbills sport casques, but the helmeted is the only species in which the front few centimetres of the casque is completely solid, making it suitable for carving.

The skull was donated to the museum collection by Philip Burton, former Principal Scientific Officer at the ornithology department, who had been given it by the eminent ornithologist Phyllis Barclay-Smith shortly before she died. The story this object tells is a complex one, combining ancient tribal beliefs, commerce, art, natural history and conservation. It takes us from this bird collection in the heart of the Home Counties, all the way to Asia and Africa, and back again. And it reveals some astonishing facts about one of the most fascinating groups of all the world’s birds: the hornbills.

Few of the world’s 230 or so bird families are quite as distinctive as hornbills. Even though most people will never have seen one in the wild, hornbills are familiar from zoos and bird collections, while their fame has spread in the last two decades or so thanks to the Disney film The Lion King. This features a hornbill named Zazu, who serves both the original lion king Mufasa and his son Simba, flying around frantically and commenting sardonically on what is going on.

As their name suggests, each of the sixty or more recognised hornbill species sports a distinctively huge bill, with that unique horny casque – sometimes huge, sometimes little more than a narrow ridge – on the top of the beak. The pioneer of evolutionary biology Alfred Russel Wallace tried to describe them for Victorian England in 1863:

The hornbills are large and clumsy birds, seldom adorned with bright-coloured plumage, but in many cases bearing a really prodigious bill … The form varies in every species, varies often in the sexes of both species, varies even in the same bird from youth to age, yet … it is always considerably curved … generally forming a sharp keel along the top.

The bill is so heavy that the hornbills’ first and second neck vertebrae (known as the atlas and axis) have fused together to allow the body to carry this heavy weight – a feature not found in any other group of birds. These unique qualities, along with molecular evidence, have recently contributed to hornbills being allocated their very own order of birds, the Bucerotiformes (a name that derives from the Greek for ‘ox horn’).

Hornbills come in many different sizes: from the red-billed dwarf hornbill of equatorial West Africa, which at 30 centimetres long and weighing between 84 and 122 grams is about the same size as a mistle thrush; to the massive southern ground-hornbill found across much of sub-Saharan Africa, which can reach a length of 1 metre and tips the scales at 4.5 kilos – equivalent to a Canada goose. Some larger individuals have been estimated to weigh 6 kilos.

They are not generally very colourful, being mainly black and white, grey or brown; but their size, shape and appearance, together with splashes of colour (usually yellow or red) on their heads and bills, make them just as striking as gaudier tropical species such as bee-eaters, kingfishers and rollers, to which they were, until recently, thought to be closely related. Some also sport large, rather attractive eyelashes – described by one scientist as the avian equivalent of sunglasses – to shade their eyes from the glare of the sun.

Hornbills are found across a broad swathe of the Old World, through the tropical and subtropical regions of Africa, Asia and Melanesia (the western Pacific). The greatest variety of species is found in west, central and east Africa, the Malay Peninsula, India, Borneo, Sumatra and the Philippines. However, fossil remains of hornbills dating from the late Miocene period (roughly 5 million years ago) have been found as far away as Morocco in north-west Africa and Bulgaria in south-east Europe.

The hornbills found in Africa and Asia display strikingly different lifestyles. All but one of the Asian hornbills live in forests, while about half of the African species are birds of the open savannah, some living in very dry, virtually desert environments. Some hornbills, such as the African grey, are widespread, while others, including the five species of tarictic hornbills of the Philippines, are confined to individual islands, and are perilously close to extinction. Incidentally the unusual name ‘tarictic’ is an onomatopoeic representation of the birds’ calls, which have a staccato quality that carries well through their forest habitat.

Hornbills are fairly catholic in their choice of food, though their diet does vary between species. Some, especially those that live in forests, eat mainly fruit, which they pluck carefully from the trees in a surprisingly delicate manner. Others, especially those on the African savannah, hunt a wide range of small animals including insects, molluscs, birds and rodents; and in the case of the two ground-hornbills, prey as large as hares, mongooses and even cobras.

They have a very distinctive feeding action: because their tongue is too short to swallow items of food held by the tip of their bill, they jerk their head back to toss them down their throat. Unlike most birds, they have binocular vision, which enables them to focus more precisely when feeding. Perhaps surprisingly, however, most never drink water, obtaining hydration directly from their food.

When hunting, several species of African hornbills will follow other creatures to find things to eat, including army ants. Two species, Von der Decken’s and eastern yellow-billed hornbills, have evolved a mutually beneficial relationship with dwarf mongooses, in which the birds act as sentries, warning of any danger from predators, while the mongooses find the food. One scientist even observed hornbills waking up the mongooses from their sleeping quarters inside termite mounds, chivvying them by calling loudly when they had overslept.

But of all the extraordinary behaviours, by far the most bizarre – and widely known – is the strange custom in which the nesting female hornbill is walled up into her nest for the whole of her incubation period. During this time she lays her eggs, incubates them, feeds the chicks, and takes advantage of being safe from predators by undergoing a full moult of her feathers. It is a common, though mistaken, belief that the male walls up the female; in fact the female usually does the work herself, using a combination of mud and her own droppings. At the last moment she enters, and the male seals the entrance shut, leaving just enough space for her to stick her beak through to be fed.

Some commentators have used this behaviour to comment on human relationships, but this apparently odd conduct is in fact perfectly sensible. Hornbills are not agile at the best of times and this keeps the nesting female and fragile offspring safe from predators such as snakes and arboreal mammals. And the male hornbill is too busy to stray, as he must constantly bring food to his mate; hence making a compelling if unromantic case why hornbills are mostly monogamous.

After hatching, the chicks grow inside the nest, defecating through the tiny entrance, so that by the time they are ready to leave, the conditions around and beneath the nest-hole can be somewhat insanitary. Finally the mother breaks through the hard mud seal – a process that can take several hours from start to finish – and they can all leave the nest.

Of all the world’s species of hornbill, perhaps the most striking is the helmeted – the bird whose skull resides in the collection at Tring. As it calls from the depths of its native home, the rainforests of Borneo and Sumatra, it sounds more like a monkey than a bird: a trumpeting sound followed by a peal of ringing laughter, which hangs as an echo in the air before fading away. Despite its large size – males can be more than 1.2 metres in length, including their long and impressive tail – this is a difficult bird to see, as it forages high in the canopy of the tallest trees, hunting for snakes, squirrels and birds, and sometimes even preying on smaller species of hornbills.

If you do catch a glimpse, be prepared for a bird that appears bizarre even by hornbill standards. The plumage is mainly dark brown, with an enormously long white tail marked with a band of black towards the tip. But it is the head and neck that are most striking: apart from the front of the casque and the tip of the bill, which are yellow, the head is bright red; and the neck is not covered with feathers, but consists of rough bare skin – red in the male and pale blue in the female.

The helmeted hornbill’s casque does indeed look rather like a helmet. It uses its weight like a hammer to dig into rotten wood or pull back pieces of tree bark to obtain food, and also as a weapon in aerial jousts between rival males (and occasionally females), usually in competition for food or nesting resources. In their authoritative The Ecology and Conservation of Asian Hornbills (2007), Margaret F. Kinnaird and Timothy G. O’Brien describe this extraordinary display: ‘When collisions occur the resulting sound – a loud CLACK! – can be heard in the forest understory at least 500 metres away. Most collisions occur while gliding, and the impact can be so powerful that one or both birds are thrown backward, performing dramatic, acrobatic flips before righting themselves and flying level.’

Despite this unusual behaviour, the casque itself is smaller than that of its relatives the great and rhinoceros hornbills. Yet it has a quality unique even among this unusual family: unlike all other hornbill casques, which are hollow and spongy, that of the helmeted hornbill is heavy and partially solid. It is this peculiar departure from the norm that may ultimately lead to the species’ downfall.

For the helmeted hornbill’s casques have long been valued in various western and Asian cultures as hornbill ivory. Also sometimes known as ‘golden jade’, the casque is neither jade nor ivory, but keratin – the same substance that makes hair, horns, hoofs and teeth in mammals. It was probably carved into ornaments by the indigenous peoples living in the species’ range – the Malay Peninsula, Sumatra and Borneo – for thousands of years. But it was only when the area was discovered by Chinese, and later European, explorers that the trade in hornbill ivory really took off.

The anthropologist and ornithologist Tom Harrisson – also the founder of the Mass-Observation social research movement in the 1930s – devoted much of his later life to the study of the birds and indigenous cultures of South East Asia. In his contribution to the landmark 1960 book Birds of Borneo he wrote:

It is likely that the casques were mainly exported raw, and worked with a heat treatment and pressing … to preserve and heighten the lovely deep golden and surface red patina of the fresh ivory … The uses of hornbill casques in Borneo are various and frequently effective; [but] while the Borneo usages persist to this day, all trace of the art of the Chinese carver seems to have vanished. Very little has survived of a remarkable craft which undoubtedly paid for many of the old jars, plates, and beads still decorating the longhouses or wives of better-off Bornean pagans many generations later.

During the Ming dynasty, which ran from the mid-fourteenth to the mid-seventeenth centuries, it is said that hornbill ivory was valued even more highly than elephant ivory. The Japanese, too, wanted this unusual product: from the seventeenth century onwards they used it as the raw material for those delicate miniature sculptures known as ‘netsuke’. The fad for collecting these exquisitely beautiful carvings soon spread to the west, and netsuke made from hornbill ivory became a much sought-after addition to the display cabinets of rich Victorian households. Those coloured red – from ivory stained by the bird’s preen gland – were especially highly prized.

Later on, live hornbills imported into Britain from Asia and Africa caused amazement among those who saw them, as their almost human-like gait, strange calls and bizarre bills were unlike any bird Europeans had ever encountered. Curiosity only increased when people learned of the birds’ strange breeding behaviour. London Zoo held a number of captive hornbills, which were always among the most popular attractions, and were regularly depicted in publications such as the Illustrated London News. Not everyone was impressed, though: Edward Stanley, the Bishop of Norwich and author of some of the most inaccurate and sentimental works on birds ever written, dismissed their ‘seemingly deformed and monstrous bills’.

But by the end of Queen Victoria’s long reign in 1901, the constant demand for hornbill ivory had led to the birds’ rapid decline. Sadly that decline has accelerated in recent years. Today hornbill ivory can reach as much as £4,000 per kilo – more than three times that for true elephant ivory – making the trade a lucrative one for organised crime syndicates. In one region alone helmeted hornbills are being killed at an estimated rate of 6,000 every year.

There is one possible piece of good news: in Indonesia, the native peoples regard the helmeted hornbill as a very special creature which guards the thin veil between life and death, ferrying souls between earth and heaven. Conservationists are now trying to enlist this ancient and sacred belief to help protect the species as it disappears at an alarming rate, by enlisting these rainforest tribes to protect both the bird and its special habitat.

Although all hornbills share the same unmistakable characteristics, together with a number of internal, morphological traits such as the fused vertebrae in their neck, two African species are considered to stand apart from the others, and have been placed in their own sub-family, Bucorvinae (the others are in the sub-family Bucerotinae). These are the northern (or Abyssinian) and the southern ground-hornbills, and they too display an intriguing combination of bizarre behaviours and cultural significance.

Whereas the other hornbills of the African savannah mostly perch on high vantage points in trees and bushes, occasionally dropping down to grab an item of prey, the two ground-hornbills mainly stay, as their name suggests, on the deck. Huge – about a metre tall – and black, with colourful wattles on the throat and around the eye (blue and red for the northern, red for the southern), and white on the wings, they walk in a slow, shuffling gait, rather like elderly gentlemen out for a stroll.

But as soon as they see potential prey, their demeanour changes. They stop in their tracks, and move slowly and carefully forward like a stalking lion, before jabbing at the ground like a pickaxe with that huge, fearsome bill, and grabbing their victim. The unfortunate animal is then despatched in the classic hornbill manner, with a jerk of the head and a rapid swallow. Their more or less exclusively carnivorous diet means that, unlike most other hornbills, they do not have a pouch beneath the bill in which to store fruit.

Ground-hornbills hunt in pairs or small packs, taking insects and other invertebrates such as snails and scorpions, or frogs and toads, for their hors d’oeuvres, and then moving on to a more substantial meal: anything from snakes and lizards to squirrels, hares and even the occasional tortoise. When feeding on snakes, including the highly venomous puff adder, the bird must use a combination of speed and its huge bill to despatch the reptile before it has the chance to bite.

The southern ground-hornbill, found across a wide swathe of southern and eastern Africa from Kenya to Botswana, has another claim to fame in the bird world. It breeds less frequently than any other species – sometimes only every three years – and is also among the longest lived of all the world’s birds, reaching up to sixty years old. Even when they do breed, only the largest male and female in the social group actually do so; the others (probably close relatives of the breeding pair) act as helpers, in a co-operative breeding strategy.

Like some birds of prey such as the larger eagles, their eggs hatch asynchronously, so that the first chick is larger and heavier than its sibling; as a result, the younger chick usually dies before it gets the chance to fledge and leave the nest. Because southern ground-hornbills are such slow breeders – sometimes rearing only one chick to adulthood every nine years – they are very vulnerable to changes in their environment; so although the species is not yet seriously threatened, it is currently in decline.

The southern ground-hornbill has a central place in African folklore and culture, which has helped protect the bird – at least until recently. Like many birds with loud calls elsewhere in the world, it is associated with the coming of the rainy season; more unusually, groups of the birds (whose sexes are very similar, though not identical) are negatively associated with homosexuality, while a Zulu word for the species, ‘Ingududu’, is used as an insult, suggesting that the recipient is not particularly intelligent. In Kenya, ground-hornbills used to be a problem on golf courses, as they would mistake stray balls for eggs and steal them. Some clubs even formulated rules to cover how to continue play when hornbills had stolen a ball.

One detailed South African study, published in the Journal of Ethnobiology and Ethnomedicine in 2014, showed that the southern ground-hornbill is also closely associated with death or some other impeding calamity; but also paradoxically seen as a protective influence against evil spirits and witchcraft. The bird is also thought to be able to use its powers to alter people’s perceptions of the world, and to be a good and accurate timekeeper (for example being able to predict changes in the seasons or the start and end of the working day).

The authors point out that some of these characteristics are helpful to the protection and survival of the species, while others may lead to its harm. They conclude that the more we know about such cultural practices and beliefs, the easier it will be to conserve the southern ground-hornbill, by encouraging positive beliefs and discouraging negative ones. Whether or not this will ultimately lead to a stabilisation in the southern ground-hornbill population and range is too early to say, but it is a good example of how to use traditional beliefs in modern conservation, by working sensitively with different cultures instead of – as has happened all too often in the past – simply dismissing these ancient beliefs as superstitious nonsense.

As we’ve seen, as well as helping to protect these unique birds, traditional beliefs can threaten them too. The rhinoceros hornbill, a huge and conspicuous black and white bird with a massive bill and casque, was described thus by Alfred Russel Wallace:

In the great rhinoceros hornbill the bill attains perhaps its greatest size and beauty, the rich hues of orange crimson and ivory white with which it is adorned in the living bird being scarcely capable of imitation … It is this bird which excited the wonder of the early voyagers to Ceylon (where a variety of it exists) who believed it to have two heads – a statement which was long credited in Europe and which may serve to teach us that the wildest and most improbable fictions of early ages had probably a foundation in some curious natural phenomenon.

Yet it is not the bill that has led the rhinoceros hornbill into trouble, but its long tail feathers, which are pure white with a black band towards the tip. For centuries the indigenous peoples of northern Borneo have coveted these striking feathers, which they use in their traditional costumes and in displays of dancing. They also make an effigy of the bird and hoist it high on the end of a pole, to summon their god of war to seek out and kill members of enemy tribes.

But this reverence comes at a price. Each group of dancers uses about 400 tail feathers, so they need to kill roughly forty birds. Because the species is so long-lived it breeds very slowly, which means that traditional hunting – especially when combined with habitat loss through logging activities – is putting too much pressure on an already rapidly dwindling population. Although hunting is illegal, it is very hard to enforce the law in such remote regions.

Ironically, the rhinoceros hornbill is the state bird of Sarawak, a part of Malaysia on the north-west of the island of Borneo, which promotes itself to tourists as ‘Sarawak – Land of the Hornbills’. Sadly this does not appear to be doing the birds much good.

Elsewhere in South East Asia, in the Philippines, a tribe living in hill country about 145 kilometres north-east of the capital Manila have long regarded rufous hornbills as deeply significant. A 1968 study calculated that more than 90 per cent of Ilongot men over twenty years old had taken at least one human head. Headhunting and hornbills are closely related in their mythology. The hornbills were understood to act as spirit birds, guiding and protecting the hunters. The bird’s shrill cry was likened to the screams of victims receiving their deathblows. The night before a raid, hunters sang in high-pitched tones to persuade the life-force of their victims to fly to them.

Skilled hunters often also wore elaborate headdresses featuring the entire beak and crest of a rufous hornbill. But it was the acquisition of hornbill earrings with dangling shell pendants (called batling) that represented the pinnacle of achievement in the life of an Ilongot boy. A man only earned the right to wear batling – or even to marry – once he had taken a head. According to the ethnographer Dr Renato Rosaldo, who spent several years doing fieldwork with the Ilongot: ‘[These] earrings announced to enemies, to allies, to family, to friends, that the person they saw before them was a formidable headhunter. Hunters wore their batling for the rest of their lives. Upon their death, the earrings were buried with them, thrown away, or given to an initiated relative.’

In north-east India, hornbills are not just part of an ancient tribal culture, but are also the centrepiece of a very modern event, the annual Hornbill Festival. Held in the state of Nagaland – known as the ‘Land of Festivals’ – during the first week of December, the event was first organised by the state government in 2000, to bring several disparate festivals under a single larger banner.

The name of the festival is a tribute to the largest species of hornbill in the country: the great (also known as the great pied or great Indian) hornbill. Found in western and north-eastern India, this large and impressive species is much admired by the Naga people for its appearance and behaviour, and has inspired some of the ornate dances and songs performed at the festival. But not all the hornbill-related events are quite so traditional: there is also a hornbill rock contest, international motor rally and photo competition, while the opening ceremony features a 100-strong choir performing a specially composed ‘Hornbill theme song’.

So what is the future for the world’s sixty-plus species of hornbills? Despite efforts to use deep-seated tribal beliefs to conserve them and their habitat, we might consider it fairly bleak. As the authors of the monumental Handbook of the Birds of the World concluded in 2001, it is reasonable to assume that despite their wide global range across much of Africa and Asia, hornbills are in decline, ‘since the habitat changes wrought by man are rarely beneficial to the members of this intriguing family’.

That destruction began thousands of years ago, with the coming of agriculture, and the widespread use of fire and axes to clear forested areas, but it has accelerated rapidly in recent decades, thanks especially to widespread logging. This particularly affects hornbills as – especially in the larger forest-dwelling species found in South East Asia – they tend to nest in the oldest trees, which are in turn the most attractive to loggers.

But we can ill afford to lose such unique and splendid birds. Nigel Collar of BirdLife International sums up both the cultural and ecological importance of all hornbills:

Hornbills hold a special attraction for all of us – one of the few kinds of bird that everyone knows, revered by tribal peoples, sought after by birdwatchers, gasped at by visitors to zoos, used by several Asian states as symbols. Yet their vital ecological function, as seed-dispersers particularly of fig-trees (which are themselves crucial components of tropical forests), is barely appreciated and poorly understood.

Back in the Natural History Museum Bird Collection at Tring, the carved skull of the helmeted hornbill serves as a timely reminder of the fragility of not just hornbills but of all tropical bird species, which are increasingly threatened by habitat loss and collecting for profit. Only by understanding their scientific and cultural significance, and working with local peoples for whom birds such as hornbills are so important to their way of life, will we stand any chance of saving these extraordinary birds.

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As when, upon a tranced summer-night,

Those green-rob’d senators of mighty woods,

Tall oaks, branch-charmed by the earnest stars,

Dream, and so dream all night without a stir,

Save from one gradual solitary gust

Which comes upon the silence, and dies off,

As if the ebbing air had but one wave.

John Keats, ‘Hyperion’

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