IELTS Academic Reading Practice Test 411

Anyone who walks in the dry bush of sub-Saharan Africa may be interrupted by a small, dull-coloured bird that flies close to the head, calls loudly and then waits, apparently expecting to be followed. If the walker does follow, the bird will lead the way, a few metres at a time, to a bees' nest hidden in a hollow tree or a termite mound. This is the greater honeyguide, a species that has formed one of the strangest partnerships in the natural world: a wild bird that deliberately guides people to food, and shares the harvest with them.

The bird itself is unremarkable to look at: about twenty centimetres long, with grey-brown plumage, to which the male adds a black throat and white cheeks, so that it resembles an oversized sparrow. Its scientific name, Indicator indicator, records its most famous habit, since indicator is Latin for 'one who points out'. The greater honeyguide belongs to a small family, found mainly in Africa, whose members are all thought to be brood parasites, and it is found south of the Sahara wherever there are bees and trees with suitable holes.

Its diet explains the relationship. Honeyguides feed mainly on the wax combs of wild bees, together with the larvae and pupae inside them, and they can digest wax, which very few animals can manage. The ability is thought to depend on microbes in the bird's gut. Wax is rich in energy but poor in nitrogen, so the birds also take adult bees and other insects. Finding a bees' nest is therefore worth a great deal to a honeyguide, but opening one is beyond the power of a bird. A person with smoke and an axe can do it in minutes, and will usually leave the wax behind.

Guiding follows a strict routine. The bird perches in front of a person, gives a chattering call, flies a short distance, stops until it is followed and then repeats the performance. When it reaches the target it waits in silence. The honey-hunter lights a fire to calm the bees, cuts open the nest and takes the honey, leaving the wax and the brood for the bird. The bird then feeds on the combs that have been exposed, and both parties leave with something of value.

Communities that hunt honey have developed distinctive calls to summon the birds, and a study published in 2016 showed that these calls are not merely decorative. Researchers working with Yao honey-hunters in northern Mozambique played recordings of the Yao call, of a bird call and of arbitrary human sounds in the bush. Honeyguides were far more likely to approach and to lead when they heard the local call, and hunters who used it were more often taken to a nest. The exchange is understood by both sides: a signal from one species changes the behaviour of the other, and each expects to gain.

Later work in Tanzania pointed in an intriguing direction. Hadza honey-hunters there use a whistle quite different from the Yao call, and the resident honeyguides responded more readily to it than to the Mozambican sound. If the birds were born knowing how to react, such a difference would be hard to explain. The result suggested that young honeyguides learn, during their first months, which sounds in their own area mean that people are willing to cooperate, and that the partnership is a local tradition rather than a fixed instinct.

The honeyguide's family life is less attractive. Like many of its relatives, the female lays her eggs in the nests of other hole-nesting birds, among them bee-eaters, barbets and woodpeckers, which then raise the young honeyguide as their own. The chick hatches with a sharp hook at the tip of its upper bill and uses it to kill the other chicks in the nest, after which it receives all the food its foster parents bring. The hook disappears as the bird grows.

It is often said that honeyguides also guide the honey badger, or ratel, a powerful animal that raids bees' nests. The story appears in many books and websites, yet reliable observations are few and some biologists doubt that the partnership is regular or important. Guiding people, by contrast, has been described in print since the sixteenth century, and honey-hunters in several countries still rely on it.

Exactly how a bird finds a nest in the first place is not fully understood. It probably watches worker bees returning to a colony and may also be drawn by the low hum of a swarm. What is clear is that the habit is not automatic: guiding appears to be confined largely to regions where people still hunt wild honey, and a bird that is not followed soon gives up.

The partnership, ancient as it is, may be changing. Commercial beekeeping, in which hives are kept in wooden boxes and harvested without the help of birds, is spreading, and cheap imported sugar has reduced the value of wild honey in some areas. Honeyguides still find nests for those who ask, but fewer people ask than once did. A habit that depends on knowledge passed between generations can disappear quickly.

Light travels poorly through water, but sound travels extremely well. In seawater, sound moves at about 1,500 metres per second, more than four times faster than in air, and low-frequency sound can cross entire ocean basins without becoming too faint to detect. Because hearing is the only sense that works over such distances, an animal that cannot hear is effectively cut off from much of its world. This is why whales, dolphins and many fish rely on sound rather than sight to find food, keep contact with their young and locate mates. It is also why noise produced by industry spreads so far.

For most of the past century the loudest sounds in the sea have come from ships. The dominant source is cavitation, the bursting of tiny bubbles as a propeller turns at speed, which produces a broad, low rumble that carries for hundreds of kilometres. A single large container ship can dominate the underwater sound field for tens of kilometres around it. Researchers who have compared recordings made decades apart in the same parts of the ocean generally report a rise in low-frequency noise, though the size of the increase varies from place to place and is difficult to establish with confidence. As global trade has grown, so has the number and size of vessels.

Other sources are more intense but less continuous. Seismic surveys searching for oil and gas tow arrays of airguns that release compressed air beneath the surface, producing a sharp pulse every ten or fifteen seconds for weeks at a time. Airguns are used because the returning echoes reveal the structure of rock far below the seabed, and no satisfactory alternative has yet been adopted on a large scale. The driving of steel tubes, known as monopiles, into the seabed to support offshore wind turbines creates some of the loudest and most damaging noises of all, especially in shallow water. Explosions, dredging and construction work add to the total.

The most dramatic evidence of harm has come from naval sonar. In 2000, several deep-diving whales, among them species of beaked whale that are rarely seen alive, stranded in the Bahamas during an exercise that used mid-frequency sonar. Beaked whales are especially vulnerable because they dive to great depths for long periods and are easily disturbed. After repeated strandings coincided with exercises near the Canary Islands, Spain restricted the use of sonar in those waters in 2004. The whales affected are thought to have been driven to the surface too quickly, suffering a condition similar to decompression sickness.

Noise can also interfere with communication without causing any obvious injury. Marine mammals use calls to maintain contact, to warn each other and to compete for mates, and a constant background rumble can hide those calls, a phenomenon known as masking. Masking matters most for animals that depend on hearing to find prey or to detect approaching predators. Some species respond by repeating themselves more often or by calling more loudly. North Atlantic right whales, for instance, were found to raise the volume of their calls as background noise rose, rather as people shout in a crowded restaurant.

Stress is harder to measure in a wild animal, but one accidental experiment provided an opportunity. After the attacks of 11 September 2001, shipping off the east coast of North America fell sharply for a time. Researchers who had been collecting the droppings of North Atlantic right whales found lower concentrations of stress hormones in the weeks that followed than in the same season of other years, when traffic was at its usual level. The finding was correlational, but the timing was striking. Such studies are rare because they depend on an unexpected change in human activity.

Fish are affected too, although the consequences are harder to see. Many species detect the movement of water with their ears. On coral reefs, experiments in which the sound of small motorboats was played over patches of reef found that young fish were caught by predators more often than in quiet conditions, partly because the noise distracted them. Other studies have shown that the natural sound of a reef guides the larvae of reef fish towards suitable places to settle, and that artificial noise can confuse that process. In the open ocean, noise from a busy shipping lane reaches places that look untouched.

What remains uncertain is how these effects add up. A population may cope with the loss of a few individuals, or it may not, and the long-term consequences of chronic noise are almost impossible to measure directly. Some researchers suspect that animals become used to constant noise; others argue that the stress carries a hidden cost. Nor is it easy to separate the effects of noise from those of pollution, overfishing and warming water, all of which act on the same animals.

The International Maritime Organization has issued guidelines on reducing noise from commercial ships, but they are voluntary, and progress has been slow. Meanwhile engineers have begun to tackle the problem at source. A bubble curtain, in which a ring of air is released around a pile driver, reduces the noise that escapes into the water, and ships can be made quieter by slowing down and by fitting better-designed propellers. Campaigners argue that quiet areas should be protected in the same way as clean air, but few governments have yet set limits on how loud the sea may be.

Few subjects provoke such agreement among politicians as the idea that schools should teach young people how to manage money. Personal debt is rising in many countries, pension arrangements have shifted from employers to individuals, and financial products are more complicated than they were a generation ago. On the face of it, the argument is unanswerable. If people are expected to make choices about mortgages, savings and loans, they should at least be taught the vocabulary in which those choices are framed. The proposal is popular with parties of almost every kind, and with the charities that advise people in debt. Financial education, in this view, is simply part of a general education, like learning to read a timetable.

Surveys of what pupils actually know lend the case some weight. The OECD has tested the financial literacy of fifteen-year-olds since 2012, and in most participating countries a substantial minority reach only the lowest level, unable to interpret a simple bank statement or to recognise a fraudulent message. Employers and consumer organisations report similar gaps: young adults who cannot read a payslip, compare two credit offers or work out what a monthly repayment will cost them over several years. The gap is widest among pupils from poorer homes, who are also the least likely to hear money discussed at home. Curricula in many countries now mention budgeting and borrowing somewhere, even if only in passing. If schools can teach pupils to read music or to dissect a plant, the argument runs, they can surely teach them to recognise an interest rate.

The sceptics do not dispute any of this. Their claim is narrower and more awkward: that teaching people about money does not reliably change what they do with it. A widely cited meta-analysis by the researchers Fernandes, Lynch and Netemeyer, published in 2014, examined the results of many programmes and found only a small effect on financial behaviour, and one that faded with time. The authors concluded that the influence of financial education on behaviour was weak, and suggested that other factors, including the moment at which a person has to make a decision, matter far more.

For many economists, the important lesson is that behaviour is shaped more by the design of the system than by knowledge. When employers were required to enrol staff in workplace pension schemes automatically, with the right to opt out, participation rose sharply, without any classroom instruction at all. Similar results have been obtained with savings schemes, where people who are invited to commit now to saving a share of future pay increases end up saving far more than they otherwise would. The insight is not that people are foolish, but that everyone's attention is limited. Such measures, their advocates argue, help even those who know nothing about compound interest, whereas lessons help only those who attend and pay attention. Critics of this position reply that a default is never neutral, since somebody has chosen it, and that an informed public is worth having for its own sake.

Yet the sceptical case is less settled than it looks. A later meta-analysis, which examined only experimental studies in which participants were assigned at random to receive financial education or not, reported larger and more durable effects than the earlier reviews. It also found that programmes worked better when they lasted long enough for pupils to practise skills, and when they were aimed at people about to make a particular decision, such as a couple taking out a mortgage. Teaching that arrives just before a choice, in other words, appears to work better than teaching intended to be useful at some unspecified point in the future.

Even those convinced of the value of the subject must contend with the practical difficulties of putting it into schools. In England, financial education became part of the secondary curriculum in 2014, but it was given no separate timetable slot; it is expected to be delivered through mathematics and citizenship, which means that the amount pupils receive varies widely from school to school. Teachers elsewhere report similar problems: a crowded curriculum, a shortage of suitably trained staff, few materials that connect with pupils' lives, and no settled agreement about what should be taught, since the financial world changes faster than textbooks. Some schools have responded by inviting local bankers into lessons, a solution that raises questions of its own.

There is also a question of fairness. Those who most need good financial teaching are often those least likely to receive it, since schools serving poorer communities struggle hardest to recruit specialist staff. Meanwhile a pupil whose parents discuss money at home arrives with much of the vocabulary already in place. Worse, teaching financial skills can be used as a substitute for regulation, shifting responsibility onto the individual: if a child has been taught to compare loan rates, the reasoning goes, the lender who hides its charges is somehow less to blame. Financial education then becomes a way of appearing to act while leaving the market unchanged.

My own view is that the case for making financial skills compulsory is strong, but only if the subject is practical, taught close to the point at which it will be used, and treated as one part of a policy that also constrains how financial products are sold. Lessons should involve deciding, not merely calculating: comparing real offers, understanding a payslip, recognising that a 'free' gift has a cost. On its own, such a course will not transform behaviour, and anyone who promises that it will is overselling it. Combined with default enrolment and honest advertising, it is well worth the timetable space.