雅思阅读 8: The Brazen Birds of the World（世界各地厚颜无耻的城市动物）

改编自 UCLA / The Conversation（2026年4月）。雅思阅读 Section 3 难度，约 1050 词。 素材来源：https://newsroom.ucla.edu/stories/city-animals-act-in-the-same-brazen-ways-around-the-world

Reading Passage

A. The urban monkeys of New Delhi are so emboldened that they will snatch lunch straight off a diner's plate. The squirrels of Manhattan behave with similar nerve. Sydney's white ibises, universally known as "bin chickens," raid rubbish bins and sandwich wrappers across the city. Such behaviour is not typical of these species in the countryside, where the same animals tend to be cautious, skittish and quick to flee from humans. Researchers have long recognised that cities are powerful agents of behavioural change, but a 2026 review led by UCLA ecologist Daniel Blumstein goes further: urban wildlife across disparate continents and evolutionary histories are converging on a remarkably similar suite of bold, human-tolerant behaviours. This "behavioural homogenisation," the authors warn, is accompanied by a quiet erosion of the very traits that animals would need to survive if they ever had to return to the wild. The review drew on studies spanning more than forty cities on five continents, and it controlled, as far as possible, for ancestry: species that were already bold in their rural populations were not counted as having changed. Even after that adjustment, the convergence remained striking, suggesting that cities do not merely favour existing variation but actively produce a new, recognisably urban animal.

B. The forces driving this convergence are not mysterious. Cities, despite their local differences, share a set of common features worldwide: they are warmer than surrounding countryside, noisy, illuminated at night and, above all, dominated by people. Because humans are typically a reliable source of food and rarely inflict harm, urban animals quickly learn not to fear them. Cities also act as selective filters: bolder individuals survive and reproduce more successfully than cautious ones, and their boldness is passed to subsequent generations. The result is a genetic shift within populations, not merely individual learning. In Sydney, sulphur-crested cockatoos have taught one another to flip open wheelie bins; in Toronto, raccoons are engaged in an accelerating evolutionary arms race with municipal wildlife managers who keep designing ever-more-resistant refuse containers. Both processes — individual learning across a single lifetime and genetic selection across generations — act together, which is why urban populations change so much faster than their rural cousins. A squirrel that learns to open a bin passes the skill on to its young by example; a squirrel whose boldness has a genetic basis passes it on through reproduction. Within a few dozen generations the two effects are difficult to disentangle.

C. Homogenisation extends beyond boldness. Urban birds, for instance, sing more alike than their rural counterparts — not because species are replacing one another, but because city noise imposes a common acoustic problem on all of them. Traffic produces low-frequency rumble, and birds whose songs are masked by it cannot communicate effectively. Those that sing louder, earlier in the morning, or at higher frequencies are the ones that find mates and reproduce. The same filtering process affects foraging: rural animals may exploit a wide range of foods and microhabitats, while urban specialists concentrate on rubbish dumps and discarded human food, even when that diet is nutritionally inferior. The buildings, bridges and road verges that cities construct become the new nesting and movement corridors, replacing the natural landmarks that rural animals once used. The same logic applies to the timing of daily activity. Many urban species now forage at different hours than their rural counterparts, shifting into the quieter parts of the day or the brighter parts of the night. Species that once shared a landscape by dividing it by habitat are, in cities, dividing it by the clock — another quiet convergence that field biologists working in a single city rarely notice.

D. The consequences are more serious than they first appear. At the population level, behavioural variation often reflects genetic variation, and genetic variation is what equips a species to adapt to future environmental shocks. If urban populations are selected for boldness and a narrow set of behaviours, they lose the flexibility that a changing climate or disease outbreak might demand. Blumstein and his colleagues draw an analogy with a diversified investment portfolio: spreading risk across a range of traits protects the population when conditions shift. A second set of consequences involves human-wildlife conflict. As animals lose their fear of people, vehicle collisions, bites, property damage and the transmission of zoonotic diseases become more frequent, and the financial costs fall on both sides. Third, homogenisation threatens locally adapted cultural behaviours — migration routes, foraging techniques, tool-use traditions and vocal dialects that are socially learned rather than genetically encoded. The critically endangered regent honeyeater of Australia, for example, has lost the song-learning models that young males need to acquire attractive breeding songs; with too few conspecifics around, males sing simplified or abnormal tunes and struggle to attract mates. The honeyeater's plight is, in miniature, what happens to any species when its population falls below the size at which social learning can be reliably transmitted. The genes may still be present, but the culture that teaches juveniles how to behave is gone — and without that culture, the genes cannot be expressed. Conservation that counts only individuals, Blumstein warns, may therefore miss the loss of behaviours that no single animal can recreate.

E. The phenomenon is not irreversible, but it requires deliberate intervention. Urban planning can retain or recreate natural foraging habitats, maintain wildlife corridors and design infrastructure that accommodates rather than excludes animal movement. Conservation programmes that reintroduce urban-adapted animals into wild settings may face unexpected resistance precisely because those animals have lost the fear and foraging skills their wild relatives possess. Ultimately, behavioural homogenisation is one more dimension of the biodiversity crisis, alongside the more familiar metrics of species loss and population decline. A world in which every city's squirrels, monkeys, ibises and raccoons behave in exactly the same bold, dependent way is a world that has traded biological richness for a kind of monotonous familiarity — and the costs, Blumstein argues, are only beginning to be counted. None of this means cities should be made unpleasant for animals, or that the boldest urban species are a problem to be solved. The point is narrower: a city designed without regard to wildlife behaviour is a city that quietly bets every species against a single, narrow way of life. The encouraging news is that the same design choices that reduce conflict — wildlife corridors, native planting, less night lighting — also preserve the variation that homogenisation currently erodes.

Questions 1-4

Choose the correct heading for paragraphs B, C, D and E from the list of headings below.

List of Headings i. Why city birds sound more alike ii. How cities select for boldness iii. The design of animal-proof rubbish bins iv. Why homogenisation is a conservation problem v. Reversing the trend and counting the costs vi. The extinction of rural bird species vii. How monkeys learned to open rubbish bins

1. Paragraph B: ____
2. Paragraph C: ____
3. Paragraph D: ____
4. Paragraph E: ____

Questions 5-8

Choose the correct letter, A, B, C or D.

5. Why do urban animals become bolder? A. They are born without fear genes. B. Food from humans rewards tameness and selection favours bold individuals. C. Rural predators have disappeared from cities. D. Cities are warmer than the countryside.

6. Why do urban birds sing at higher frequencies? A. To attract mates over longer distances. B. To avoid being drowned out by low-frequency traffic noise. C. Because they have fewer competitors in cities. D. Because buildings echo high-frequency sounds better.

7. The "diversified investment portfolio" analogy is used to argue that A. urban animals should be insured against traffic accidents. B. genetic and behavioural diversity protects species from future shocks. C. cities should invest in wildlife management infrastructure. D. bold animals are a poor financial bet for conservation.

8. What problem do regent honeyeaters face? A. They cannot find enough food in urban areas. B. They have lost the wild habitats they need for migration. C. They lack older birds to teach them species-typical songs. D. They are being outcompeted by more aggressive urban species.

Questions 9-13

Do the following statements agree with the claims of the writer?

Write:

• TRUE if the statement agrees with the information
• FALSE if the statement contradicts the information
• NOT GIVEN if there is no information on this

9. Behavioural homogenisation occurs only among mammal species.
10. Urban animals often rely on a narrower range of foods than rural ones.
11. Reintroducing urban animals to the wild is always straightforward.
12. The regent honeyeater is classified as critically endangered.
13. Blumstein's research was funded by the Sydney city council.

Questions 14-15

Complete the summary below using NO MORE THAN TWO WORDS from the passage.

Cities act as selective filters, favouring animals that are (14) __________ and tolerant of humans. Over time, this process erodes (15) __________ variation, leaving populations less able to adapt to future change.

答案与解析

← 上一篇 | 返回雅思焦点 | 下一篇 →