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IELTS Reading Passage 2: Intelligent Behaviour in Birds
Many people are aware of the intelligence of chimpanzees and
other mammals.
However, birds also demonstrate intelligent behaviour.
A
For centuries, many scholars maintained that humans were the only intelligent
organisms on Earth. Many traits were considered to be exclusively human
examples of acumen – for example, language, tool use, deception, awareness of
self and others. However, exciting new research on a number of animals,
particularly birds, has called into question the uniqueness of these traits,
forcing us to reconsider this opinion. In 1964, people were amazed when
naturalist Jane Goodall first discovered chimpanzees making and using tools.
But ornithologists, people who study birds, were not overly surprised. Almost
20 years earlier, a renowned ornithologist had shown that tool use was
commonplace in populations of woodpecker finches residing on the Galápagos
Islands. These tiny birds routinely used twigs to extract grubs from tree bark.
B
Since then, the catalogue of tool-using animals has grown. At least three
Australian bird species make tools similar to those of the woodpecker finch,
and some white-winged choughs can access shellfish they have been known to use
rocks as hammers to crack open the recalcitrant shells. Other birds show a more
sophisticated level of insight. For example, black kites have been reported
dropping bits of lit bark to ignite bush fires at the edge of the forest,
thereby making them easier to catch as kites enjoy big fires that produce smoke
and grass. A more recent example is a black kite observed picking up a
smouldering straw, and re-igniting the dropped bushfire to continue its
food-hunting strategy across trees. The bird then dropped it again and so on –
as if it understood the current means.
C
Most tool-using behaviours are a means of extracting food, which may provide a
clue as to how the birds are able to meet food use. Indeed, tool innovation may
be especially important in areas of seasonal food scarcity. But biologists and
physiologists have also noticed that such advanced expression of skill may be
underpinned by an increase in brainpower. Cognitive capabilities required to
make tools and use them suggest birds possess intellectual capabilities
equalling or exceeding those of monkeys and apes. Several studies have found a
positive correlation between an individual bird’s dietary breadth and its
superiority of intelligence. For example, omnivorous birds (those that eat
insects, seeds, and fruits) such as birds of prey, live in a more challenging
and less supply-defined habitat, and are significantly more intelligent than
birds that eat more restricted diets. If food may be distributed sporadically,
or retrieved with more cognitive effort, then intelligent birds may be the most
successful. If there are new resources needed to feed offspring, this too may
affect intelligence in generation will influence the next.
D
New Caledonian crows boast many different tools in their tool kit. They use a
hooked tool made by removing all but one of the side branches from a twig. They
fashion serrated leaves (that behave better as scissors) from pandanus leaves.
They also make probes by modifying their own moulted feathers. Each tool is
used in slightly different ways to pull grubs from deep within tree trunks. The
crows carry their favourite tool from one foraging site to the next. They also
store their tools for later re-use in a secure place on their perch. Problem-solving
abilities have traditionally been thought to be beyond the reach of animals.
Nevertheless, birds are coming up with innovative solutions all the time.
Recently, New Caledonian crows were observed moulding a piece of wire,
something they had never seen before, into a hook and then using it to retrieve
food.
E
Literally hundreds of such reports have accumulated in back copies of
scientific journals. Recently, a team of biologists from McGill University in
Canada collated them and compared the frequency and size of innovations with
the size of the birds’ forebrain (the brain-area responsible for higher-order
information processing) relative to the hindbrain. The team uncovered a clear
relationship: birds with relatively large forebrains are able to invent fresh
solutions to ecological challenges, and to exploit the discoveries and
inventions of others, more often than birds with relatively small forebrains.
F
Intelligence in birds may also arise as a result of selection to overcome the
dynamic challenges of communal living. Since this involves competition between
group members, to be successful, a social animal may need to be able to reflect
on its own intentions, and those of others. The consequence of being part of a
community may be the evolution of a distinctly ‘political’ brain.
G
What better way to exercise a political brain than to be deceitful? Perhaps the
best example of deception among birds comes from the white-winged choughs.
Choughs are cooperative breeders; that is, they form a communal group
consisting of a breeding pair and up to 15 non-breeding ‘helpers’. However, if
they are orphaned too young, choughs have so little enthusiasm for foraging, or
gathering food, that they are often too underweight to survive. It is thought
that, to compensate, brood-patch adults who provide the help, young choughs
plead so intensely for food – even when each adult is watching another – that
food will almost always be provided. For example, a chough is likely to perform
the high-pitched begging display when an adult is already feeding another chick
in the group! By doing this, they trick the adult into feeding them. A young
chough in a big social group is more likely to be fed than a solitary chick in
a nest. It also seems that choughs may steal the chicks of rival groups to add
to their own – and this act of social trickery is strengthened by the way in
which all choughs look and act so similar. It is likely that these young are
accepted as one of their own and the frantic trial is set to prevent the group as
a sign of sight will fool the foster parents. It’s likely that these choughs
also cheat to win access to mates. In fact, the ones who are watching because
they are concerned about their own status. Choughs need other choughs to like
them as they cannot breed without social aid.
📘 Questions 14–20: Matching Headings
Choose the correct heading for each paragraph (A–G) from the
list below.
Write the correct number, i–x, in boxes 14–20.
List of Headings
i. The theory linking capacity for tool use in birds and
survival
ii. The influence of humans on tool use
iii. The theory linking cognitive ability and living in a society
iv. Reviewing long-held beliefs
v. Intelligence helps birds to remember
vi. How some birds trick each other
vii. Physiological evidence of birds’ intelligence
viii. Several examples of birds who use tools
ix. One species’ multiple tool-using techniques
x. Physical evidence of birds’ intelligence
14. Paragraph A
15. Paragraph B
16. Paragraph C
17. Paragraph D
18. Paragraph E
19. Paragraph F
20. Paragraph G
🐦 Questions 21–26:
Matching Features with Birds
Look at the following characteristics and the list of birds
below.
Match each characteristic with the correct bird, A, B, or C.
Write the correct letter, A, B, or C,
in boxes 21–26.
NB: You may use any letter more than once.
Characteristics:
21. Keeping tools that they like to use
22. Drawing out their prey by frightening it
23. The use of tools to remove the outer covering from food
24. Using food to attract their prey
25. The use of unfamiliar materials to make tools
26. Engaging in certain activities for the benefit of observers
List of Birds:
A. White-winged choughs
B. Black kites
C. New Caledonian crows
📘 Questions 14–20 – Matching Paragraph Headings
14. Paragraph A
✅ Answer: iv. Reviewing long-held beliefs
📍 Line: "For centuries, many scholars maintained that humans were the only intelligent organisms on Earth."
💡 Explains how new discoveries about birds challenge the old belief that only humans are intelligent.
15. Paragraph B
✅ Answer: viii. Several examples of birds who use tools
📍 Line: "Since then, the catalogue of tool-using animals has grown."
💡 Gives multiple examples of birds like black kites and choughs using different tools.
16. Paragraph C
✅ Answer: i. The theory linking capacity for tool use in birds and survival
📍 Line: "Tool innovation may be especially important in areas of seasonal food scarcity."
💡 Suggests tool use is directly tied to birds’ ability to survive when food is limited.
17. Paragraph D
✅ Answer: ix. One species’ multiple tool-using techniques
📍 Line: "New Caledonian crows boast many different tools in their tool kit."
💡 Focuses only on one species using many types of tools (twigs, feathers, leaves, wire).
18. Paragraph E
✅ Answer: vii. Physiological evidence of birds’ intelligence
📍 Line: "Birds with relatively large forebrains are able to invent fresh solutions..."
💡 Highlights a scientific study linking brain size to innovation ability.
19. Paragraph F
✅ Answer: iii. The theory linking cognitive ability and living in a society
📍 Line: "Intelligence in birds may also arise as a result of selection to overcome the dynamic challenges of communal living."
💡 Shows that living in social groups pushes birds to develop intelligence.
20. Paragraph G
✅ Answer: vi. How some birds trick each other
📍 Line: "What better way to exercise a political brain than to be deceitful?"
💡 Gives examples of choughs tricking adults into feeding them or stealing chicks.
🐦 Questions 21–26 – Match the Bird with the Characteristic
21. Keeping tools they like to use
✅ Answer: C. New Caledonian crows
📍 Line: "The crows carry their favourite tool from one foraging site to the next. They also store their tools for later re-use..."
💡 Shows preference and reuse — signs of intelligence and memory.
22. Drawing out their prey by frightening it
✅ Answer: B. Black kites
📍 Line: "Black kites... dropping bits of lit bark to ignite bush fires... thereby making them easier to catch."
💡 They scare prey out into the open using fire.
23. The use of tools to remove the outer covering from food
✅ Answer: C. New Caledonian crows
📍 Line: "Used in slightly different ways to pull grubs from deep within tree trunks."
💡 They remove bark or dig out insects using tools.
24. Using food to attract their prey
✅ Answer: B. Black kites
📍 Line: "Picking up a smouldering straw, and re-igniting the dropped bushfire..."
💡 The fire acts as bait, bringing prey (like insects) out.
25. The use of unfamiliar materials to make tools
✅ Answer: C. New Caledonian crows
📍 Line: "Observed moulding a piece of wire... into a hook and then using it to retrieve food."
💡 They had never seen wire before, but adapted to it creatively.
26. Engaging in certain activities for the benefit of observers
✅ Answer: A. White-winged choughs
📍 Line: "A chough is likely to perform the high-pitched begging display when an adult is already feeding another chick..."
💡 They fake hunger or show off to get fed — performing for attention.
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