IELTS Academic Reading Practice Test 444

Among the most unusual structures built by any animal are the bowers of the bowerbirds, a family of roughly twenty species found in New Guinea, eastern Australia and a few nearby islands. A bower is not a nest. It is a display ground, constructed by the male and used only to attract a mate; the female builds a separate, ordinary cup nest in a tree and raises the chicks without any help from him. The male's structure, by contrast, has no roof, no eggs and no young, and may be rebuilt or abandoned within a single season.

Bowers take three main forms. The simplest is the court, a cleared patch of ground where a male arranges leaves, stones or snail shells. The maypole bower consists of sticks piled around a sapling or a pair of upright stems, sometimes with a small hut of orchid stems or moss at the base. Best known is the avenue bower: two parallel walls of twigs, planted upright in the ground, enclosing a floor that the male sweeps clean and decorates.

The satin bowerbird of eastern Australia builds a true avenue and paints it. The male chews berries and then, holding a wad of fibrous bark in his beak like a brush, applies the pulp to the inner walls, so that the passage is stained a colour that varies from yellow to dark purple. His decorations are overwhelmingly blue: feathers, flowers, berries and, in recent decades, bottle tops, drinking straws and clothes pegs. Neighbouring males raid one another's bowers, and a bird whose decorations have been stolen will often replace them within hours.

Farther north, the great bowerbird decorates the ground in front of its avenue with pale objects — bones, shells and white stones — laid out on a court of sticks. A study published in 2010 reported that these objects are not placed at random. Small items are put close to the bower and larger ones farther away, and the court is graded so smoothly that a female standing inside the avenue sees the collection at a fairly uniform size. The researchers argued that the arrangement creates a visual illusion, and that males whose courts are most consistent attract the most visitors.

The Vogelkop bowerbird of the mountains of western New Guinea builds what is often described as a hut: a dome of orchid stems around a central pole, approached across a carpet of moss that the male keeps free of debris. He collects fruit, flowers, beetle wings and other bright objects and sorts them into piles by colour, keeping the most vivid items nearest the display area. When his supply of a particular colour runs low, he may fly a considerable distance to find a replacement.

Not every member of the family builds an elaborate structure. The tooth-billed bowerbird of the Queensland rainforest clears a small court and lays leaves upon it, pale side upward, but builds nothing else. The golden bowerbird, one of the smallest of the group, lives in the cooler uplands and builds two towers of sticks joined by a horizontal perch. The regent bowerbird, a striking black and gold bird, builds a small avenue and, like the satin bowerbird, paints its walls.

Whatever the design, the bower is only a stage. The male displays by calling, fanning his wings and dancing around the female, who visits briefly and then leaves. She may inspect several bowers before choosing, and each visit is short. Judgement is quick, and the male has no further role in raising the offspring.

Some species add sound to the performance. Satin bowerbirds are accomplished mimics, and their displays may include the calls of currawongs, kookaburras and other local birds, along with sounds that appear to be learned from their surroundings. A male may alternate between dancing, calling and rearranging his decorations for long periods while he waits for a female to appear.

Males do not build well at first. Young males spend several years practising: they watch older birds, construct untidy bowers that they later destroy, and steal decorations before they have a bower of their own. It takes a male satin bowerbird about seven years to acquire the glossy blue-black plumage of an adult, with its pale lavender eye, and the birds that hold the best sites and attract the most females are usually the oldest. Skill, in other words, improves with age, and the bower advertises that skill.

Maintaining a bower is laborious. Sticks must be replaced as they rot, the floor swept and the decorations rearranged after rain or theft. Rival males may wreck a neighbour's walls in minutes, and the owner must begin again. Yet males are extraordinarily persistent: a single bird may spend months of the year in repair and display. Bowers are often rebuilt on the same site in successive years.

Charles Darwin discussed bowerbirds in The Descent of Man, remarking on the pleasure they appeared to take in decoration, and the family has been studied closely ever since as an example of sexual selection — the process by which traits are favoured because they bring reproductive success rather than a better chance of survival. Bowerbirds also matter to their forests. Most species eat fruit, and as they move between patches of rainforest they disperse the seeds of many trees. Clearance for timber and agriculture has reduced the available habitat in parts of New Guinea and eastern Australia.

A wildfire is not a single object but a chain of small ignitions. For flames to spread, three things must be present: fuel, oxygen and heat. In the open air, oxygen is rarely the limiting factor, so what matters is the state of the fuel and the way heat travels from burning material to material that has not yet caught. Heat moves by radiation through the air, by convection in rising gases and by conduction through solid objects.

The fuel itself varies enormously. Fine fuels — grass, needles, fallen leaves and small twigs — have a large surface area in proportion to their weight, so a small amount of heat raises them to the temperature at which they release flammable gases and ignite. Moisture matters just as much. Water absorbs a great deal of heat as it turns to steam, so damp fuel delays ignition and slows the advance of the flames; fires therefore generally die down overnight, when humidity rises and dew forms.

Topography shapes the fire as well. A flame leans towards whatever lies above it, and on a slope the ground itself rises towards the unburnt fuel, so the flames sit closer to it and heat it more efficiently. Fires therefore tend to run uphill, sometimes quickly, and to creep downhill. Canyons and gullies can funnel hot gases and preheat everything above them, producing sudden surges that surprise even experienced crews.

Wind is the factor that forecasters watch most closely. It supplies fresh oxygen, bends the flames towards unburnt fuel and carries heat into the vegetation ahead, so a fire driven by a strong wind can advance many times faster than one burning in still air. A change in wind speed or direction is the commonest cause of a sudden change in behaviour, and a shift of wind can turn a long flank of flame into a new front.

Fires are usually classified by what they are burning. A surface fire consumes litter, grass and low shrubs. A ground fire burns beneath the surface, in roots, buried wood or peat, where it can smoulder for weeks or months and break out again long after the flames above have been put out. A crown fire travels through the tops of trees; it is the most violent and the least controllable, and it is usually fed by a surface fire beneath it. A spot fire begins some distance from the main fire, when a burning fragment lands on dry fuel.

Spotting, as this process is called, is one of the least predictable features of a large fire. Under the right conditions, pieces of bark, cones or twigs are lifted into the plume of hot gas above the flames and carried hundreds of metres, sometimes several kilometres, before they fall. The bark of many eucalyptus trees peels in long ribbons that burn fiercely while they tumble, and these are notorious sources of spot fires in Australia. Fragments carried in this way are known as firebrands. In North America, burning material from conifers can be lofted high enough to start fires well beyond a firebreak.

A surface fire becomes a crown fire when flames reach the lowest branches and then climb through the layers of vegetation known as ladder fuels — suppressed saplings, hanging bark and low limbs — that connect the ground to the canopy. Once a crown fire is running, wind and slope together can drive it forward at great speed, and radiant heat from the flames is intense enough to ignite the foliage of trees several metres away. Suppression then becomes almost impossible, because crews cannot work beneath a burning canopy.

The most dangerous behaviour, however, arises when a fire creates its own weather. The rising plume of hot gas can form a towering cloud, and in some cases this develops into a thunderstorm known as a pyrocumulonimbus, which may produce lightning, strong downdraughts and sudden changes in wind direction on the ground. Rotating columns of flame, or fire whirls, have also been observed, though they are rare and difficult to study. Firefighters describe fires that appear to stop, only to surge forward minutes later. Researchers acknowledge that such events are poorly understood and that no current model predicts them reliably.

Computer models of fire spread divide a landscape into small cells and calculate how quickly each one will ignite. They combine wind, slope, fuel type and moisture, and they are useful for warning the public and positioning crews. Fuel moisture, however, is estimated from satellite images or measured at a handful of weather stations rather than observed across a whole landscape, and the physics of a large fire, with its own wind field and columns of rising air, is simplified considerably. Models are also tuned to the fires that have been recorded, which are rarely the most extreme.

In many parts of the world, a century of extinguishing every fire as quickly as possible has allowed brush and small trees to accumulate, so that when a fire does start there is far more fuel to burn than there would have been under a regime of frequent, mild burning. Land managers now set controlled fires in cool, damp conditions to reduce this load, following practices that some Indigenous peoples have used for thousands of years. Whether such burning can be scaled up fast enough, where houses are scattered among the trees, is an open question.

Almost every well-known festival now has a sponsor, a ticket price and a marketing campaign. Companies pay to have their names attached to processions and stages; local authorities count the visitors and the hotel bookings; and the event itself is broadcast, photographed and sold. It is reasonable to ask whether this commercial apparatus damages the practices it surrounds, and many people assume that it does. In my view the question cannot be answered with a general yes or no, because the damage, where it occurs, depends less on money than on who is making the decisions.

The strongest version of the critical case comes from anthropology and from the sociology of tourism. Its central concept is commodification: the transformation of a practice into a product. Once a ritual is packaged for outsiders, the argument runs, its elements are rearranged to suit the paying audience. Long ceremonies are shortened to fit a schedule; moments that were private become performances; and participants begin to value the version that visitors will pay to see. What is lost, on this account, is not the outward form but the internal meaning — the reason the practice existed in the first place. The claim is not that money corrupts in itself, but that the market rewards simplification, and that this changes what participants understand their festival to be.

Against this must be set the economic argument, which is not merely special pleading by sponsors. Festivals cost money: costumes, instruments, travel, venues and the time of people who might otherwise be earning. Where public funding has fallen, commercial income can keep an event alive that would otherwise have disappeared, and it can pay performers who were previously expected to work for nothing. Organisers also point out that sponsorship may bring skills — accountancy, publicity, ticketing — that small community groups do not possess. The money, in other words, is a means and not only a threat.

The debate is further complicated by the fact that authenticity is a poor test. Historians Eric Hobsbawm and Terence Ranger, in a collection published in 1983, showed that many traditions presented as ancient were invented within living memory, often deliberately, for political or commercial purposes. Festivals have always borrowed from neighbours, absorbed new instruments and dropped old ones. To ask whether a celebration is 'genuine' is therefore to ask the wrong question, since the answer would condemn changes that have been happening for centuries.

A more useful distinction, it seems to me, is between change that comes from within a community and change that is imposed upon it. A village that decides to open its harvest festival to visitors, and argues about how much to show them, is in a different position from a village whose festival is redesigned by an outside agency and sold as a package. In the second case the people concerned have lost the ability to say what the event is for, and that, rather than the presence of money, is where the harm lies. This is not an argument against visitors: communities have every right to decide that a wider audience is welcome, and many do.

International recognition complicates matters further. In 2003 UNESCO adopted a convention on safeguarding what it calls intangible cultural heritage, and inclusion on its lists can bring both prestige and tourists. It is often said that listing renews interest among young people, and it sometimes brings grants and invitations to perform abroad. Others complain that listing freezes a practice at a particular moment, or that the resulting attention encourages a shortened version designed for visitors. The outcomes appear to depend heavily on local circumstances, which is precisely what a list cannot capture.

Evidence is thin, and not only because the concepts are slippery. Measuring meaning is difficult; researchers rely on interviews and observation, usually at a single festival and over a short period. Comparisons are rare, so it is hard to know whether a practice would have declined anyway, and studies are more likely to be carried out where there is a conflict to report than where a commercial partnership has worked quietly for twenty years. Funding for long-term fieldwork is scarce, and few researchers can afford to follow the same community for a decade. Claims that commercialisation harms culture, or that it rescues it, therefore often rest on less than they appear to.

None of this means that anything done in the name of a tradition is acceptable. Two safeguards seem to me essential. The first is that the community, including those who are not performers, keeps control of decisions about what may be shown and what may not. The second is that the income is shared, since a festival that enriches an agency while leaving its musicians unpaid has simply transferred value away from the practice. Where both conditions hold, commercial success is not a threat to a festival but a means by which it survives. The question to ask is not whether money is involved, but who holds it and who decides. A festival worth keeping will survive a good deal of attention, provided that the people who keep it are the ones who decide.