Bird Migration Theory - IELTS Listening Answers & Explanations
From Cambridge IELTS 17 Academic Listening Test 3 · Part 4 · Questions 31–40
Audio
Questions
Questions 31–40 Note Completion
Complete the notes below.
Write ONE WORD ONLY for each answer.
Bird Migration Theory
Most birds are believed to migrate seasonally.
Hibernation theory
- It was believed that birds hibernated underwater or buried themselves in 31.
- This theory was later disproved by experiments on caged birds.
Transmutation theory
- Aristotle believed birds changed from one species into another in summer and winter.
– In autumn he observed that redstarts experience the loss of 32 and thought they then turned into robins.
– Aristotle’s assumptions were logical because the two species of birds had a similar 33.
17th century
- Charles Morton popularised the idea that birds fly to the 34 in winter.
Scientific developments
- In 1822, a stork was killed in Germany which had an African spear in its 35.
– previously there had been no 36 that storks migrate to Africa
- Little was known about the 37 and journeys of migrating birds until the practice of ringing was established.
– It was thought large birds carried small birds on some journeys because they were considered incapable of travelling across huge 38 .
– Ringing depended on what is called the ‘39’ of dead birds.
- In 1931, the first 40 to show the migration of European birds was printed.
Answers & Explanations Summary
| # | Answer | Evidence | Explanation |
|---|---|---|---|
| Q31 | mud | Another theory for the regular appearance and disappearance of birds was that they spend winter hidden in mud till the weather changed and food became abundant again. | Excerpt/Transcript Explanation: The transcript suggests that there was a theory suggesting that birds spend the winter hidden in mud until the weather changes and food becomes abundant again. Answer Explanation: The answer 'mud' refers to the idea that birds might hide in mud during the winter to survive until better conditions return. Reason For Correctness: The correct answer is 'mud' because it fits perfectly with the theory mentioned in the excerpt that birds could be hidden in mud during the winter. This aligns with the concept of hibernation or temporary shelter for survival, as birds were thought to disappear and then reappear when conditions improved. |
| Q32 | feathers | He observed that in the autumn, small birds called ‘redstarts’ began to lose their feathers | Excerpt/Transcript Explanation: The transcript talks about observing small birds losing their feathers in the autumn season. Answer Explanation: The answer 'feathers' refers to the body coverings of birds that they lose during molting cycles. Reason For Correctness: The correct answer is feathers because the excerpt mentions the specific observation of small birds losing their feathers in autumn, highlighting a crucial aspect of bird physiology related to their seasonal changes. |
| Q33 | shape | These assumptions are understandable given that this pair of species are similar in shape, but are a classic example of an incorrect interpretation based on correct observations. | Excerpt/Transcript Explanation: The transcript describes how a mistake was made in assuming that one bird species could transform into another based on their similar appearance. Answer Explanation: The answer 'shape' refers to the physical form or appearance of the birds. Reason For Correctness: The correct answer fits because the misunderstanding discussed in the transcript revolves around the similarity in shape between the two bird species, which led to the incorrect belief in transmutation theory. |
| Q34 | moon | He wrote a surprisingly well-regarded paper claiming that birds migrate to the moon and back every year. | Excerpt/Transcript Explanation: The transcript talks about someone who wrote a paper saying that birds go to the moon and come back every year. Answer Explanation: The answer refers to the moon, which is Earth's natural satellite that shines in the sky at night. Reason For Correctness: The correct answer matches the idea in the excerpt where someone believed birds migrated to the moon, connecting the mention of the moon in the answer to the context of birds' migration in the text. |
| Q35 | neck | This particular stork made history because of the long spear in its neck which incredibly had not killed it | Excerpt/Transcript Explanation: The transcript talks about a stork that was found with a long spear in its neck. Surprisingly, the stork was still alive despite the spear in its neck. Answer Explanation: The answer refers to the 'neck' of the stork, which is the part of the body where the long spear was found. Reason For Correctness: The correct answer is 'neck' because it correctly identifies the body part of the stork where the spear was lodged based on the description in the excerpt. |
| Q36 | evidence | This was a truly defining moment in the history of ornithology because it was the first evidence that storks spend their winters in sub-Saharan Africa. | Excerpt/Transcript Explanation: The transcript talks about a significant moment in the study of birds where they found proof that storks spend their winters in a specific part of Africa. Answer Explanation: The answer refers to something that helps prove a theory or idea. Reason For Correctness: The correct answer fits perfectly because the excerpt mentions the first evidence that supported the idea of storks migrating to Africa during winters. This evidence supported and strengthened the existing theory of bird migration. |
| Q37 | destinations | Before this, very little information was available about the actual destinations of particular species and how they travelled there. | Excerpt/Transcript Explanation: The transcript mentions that before a certain point in time, not much was known about where specific bird species went during migration and how they made their journeys. Answer Explanation: The answer means the places where birds travel to during migration. Reason For Correctness: The correct answer matches because it reflects the information provided in the excerpt about the limited knowledge regarding the destinations of migrating birds prior to the establishment of methods like ringing to track their movements. |
| Q38 | oceans | This idea came about because it seemed impossible that small birds weighing only a few grams could fly over vast oceans. | Excerpt/Transcript Explanation: The transcript mentions that people previously thought small birds couldn't fly over vast oceans because they weighed so little. Answer Explanation: The answer 'oceans' refers to the large bodies of water that cover much of the Earth's surface. Reason For Correctness: The correct answer is 'oceans' because the excerpt specifically talks about small birds crossing vast oceans, indicating that the idea of small birds flying over oceans was previously thought to be impossible based on their size. |
| Q39 | recovery | The development of bird ringing, by a Danish schoolteacher, Hans Christian Cornelius Mortensen, made many discoveries possible. This is still common practice today and relies upon what is known as ‘recovery’ | Excerpt/Transcript Explanation: The transcript talks about how a Danish schoolteacher named Hans Christian Cornelius Mortensen developed a method known as bird ringing to make many discoveries possible. Answer Explanation: The answer refers to 'recovery', which is a crucial aspect of bird ringing and is still used today. Reason For Correctness: The correct answer is 'recovery' because the excerpt mentions that bird ringing relies on 'recovery,' which implies finding or reencountering the birds that were previously tagged or ringed. This process helps researchers track the movements and behaviors of birds during migration. |
| Q40 | atlas | Huge amounts of data were gathered in the early part of the twentieth century and for the first time in history people understood where birds actually went to in winter. In 1931, an atlas was published showing where the most common species of European birds migrated to. | Excerpt/Transcript Explanation: The transcript talks about a book that was made in 1931 showing where common European birds went during the winter. Answer Explanation: The answer refers to a book or publication called an 'atlas'. Reason For Correctness: The correct answer is 'atlas' because it fits the context of a publication or book that contains maps or information related to specific topics. In the excerpt, it mentions an atlas being published in 1931 that showed where European birds migrated to, indicating the use of a book containing such detailed information. |
Transcript
Scientists believe that a majority of the earth’s bird population migrate in some fashion or other. Some travel seasonally for relatively short distances, such as birds that move from their winter habitats in lowlands to mountain tops for the summers. Others, like the Arctic Tern, travel more than 25,000 miles seasonally between the northern and southern poles. Bird migration has been studied over many centuries through a variety of observations.
But until relatively recently, where birds went to in the winter was considered something of a mystery. The lack of modern science and technology led to many theories that we now recognize as error-filled and even somewhat amusing. Take hibernation theory for example – two thousand years ago, it was commonly believed that when birds left an area, they went underwater to hibernate in the seas and oceans. Another theory for the regular appearance and disappearance of birds was that they spend winter hidden in mud till the weather changed and food became abundant again. The theory that some birds hibernate persisted until experiments were done on caged birds in the 1940s which demonstrated that birds have no hibernation instinct.
One of the earliest naturalists and philosophers from ancient Greece was Aristotle who was the first writer to discuss the disappearance and reappearance of some bird species at certain times of year. He developed the theory of transmutation, the seasonal change of one species into another, by observing redstarts and robins. He observed that in the autumn, small birds called ‘redstarts’ began to lose their feathers, which convinced Aristotle that they changed into robins for the winter, and back into redstarts in the summer. These assumptions are understandable given that this pair of species are similar in shape, but are a classic example of an incorrect interpretation based on correct observations.
The most bizarre theory was put forward by an English amateur scientist, Charles Morton, in the seventeenth century. He wrote a surprisingly well-regarded paper claiming that birds migrate to the moon and back every year. He came to this conclusion as the only logical explanation for the total disappearance of some species.
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One of the key moments in the development of migration theory came in 1822 when a white stork was shot in Germany. This particular stork made history because of the long spear in its neck which incredibly had not killed it – everyone immediately realised this spear was definitely not European. It turned out to be a spear from a tribe in Central Africa. This was a truly defining moment in the history of ornithology because it was the first evidence that storks spend their winters in sub-Saharan Africa. You can still see the ‘arrow stork’ in the Zoological Collection of the University of Rostock in Germany.
People gradually became aware that European birds moved south in autumn and north in summer but didn’t know much about it until the practice of catching birds and putting rings on their legs became established. Before this, very little information was available about the actual destinations of particular species and how they travelled there. People speculated that larger birds provided a kind of taxi service for smaller birds by carrying them on their backs. This idea came about because it seemed impossible that small birds weighing only a few grams could fly over vast oceans. This idea was supported by observations of bird behaviour such as the harassment of larger birds by smaller birds.
The development of bird ringing, by a Danish schoolteacher, Hans Christian Cornelius Mortensen, made many discoveries possible. This is still common practice today and relies upon what is known as ‘recovery’ – this is when ringed birds are found dead in the place they have migrated to, and identified. Huge amounts of data were gathered in the early part of the twentieth century and for the first time in history people understood where birds actually went to in winter. In 1931, an atlas was published showing where the most common species of European birds migrated to. More recent theories about bird migration …