Great Migrations — IELTS Reading Answers

Local gulls and migrating arctic terns behave in the same way when offered food.

“While local gulls will dive voraciously for such handouts, the tern flies on.”

Gulls dive voraciously for such handouts while the tern flies on, so their responses are opposite rather than the same.

Experts’ definitions of migration tend to vary according to their area of study.

“But migration is a complex issue, and biologists define it differently, depending in part on what sorts of animals they study.”

Biologists define migration differently depending in part on what sorts of animals they study, confirming definitions vary by area of study.

Very few experts agree that the movement of aphids can be considered migration.

“So can the movement of aphids when, having depleted the young leaves on one food plant, their offspring then fly onward to a different host plant, with no one aphid ever returning to where it started.”

The text includes aphid movement within migration, but it never reports how many experts agree, so very few is unsupported.

Aphids’ journeys are affected by changes in the light that they perceive.

“They allow for the fact that, for example, aphids will become sensitive to blue light (from the sky) when it’s time for takeoff on their big journey, and sensitive to yellow light (reflected from tender young leaves) when it’s appropriate to land.”

Aphids become sensitive to blue light for takeoff and to yellow light for landing, so changes in the light they perceive direct their journeys.

Dingle’s aim is to distinguish between the migratory behaviours of different species.

“therefore helps guide researchers towards understanding how evolution has produced them all.”

Dingle's definition is meant to cover all the behaviours and show how evolution has produced them all, not to separate the species' behaviours.

According to Dingle, migratory routes are likely to

“they tend to be linear, not zigzaggy”

Dingle says migratory routes tend to be linear, not zigzaggy, ending with the idea that routes are direct, option G.

To prepare for migration, animals are likely to

“they involve special behaviours concerning preparation (such as overfeeding) and arrival”

Preparation involves special behaviours such as overfeeding, which completes the sentence about getting ready, option C.

During migration, animals are unlikely to

“which keeps them undistracted by temptations and undeterred by challenges that would turn other animals aside.”

Migrating animals stay undistracted by temptations, so stopping to exploit them is unlikely, option A.

Arctic terns illustrate migrating animals’ ability to

“Right now it is totally focused on the journey; its undivided intent is arrival.”

The arctic tern's undivided intent is arrival, showing the capacity to stay focused on the destination, option E.

“Pronghorn, dependent on distance vision and speed to keep safe from predators”

The gap pairs with distance vision as what pronghorn rely on to escape predators; the passage names speed.

“One population, which spends the summer in the mountainous Grand Teton National Park of the western USA, follows a narrow route from its summer range in the mountains, across a river, and down onto the plains.”

The gap is where the route descends after the mountains and river; the passage says down onto the plains.

“These pronghorn are notable for the invariance of their migration route and the severity of its constriction at three bottlenecks.”

The gap names the three narrow points where the route constricts; the passage calls them three bottlenecks.

“At one of the bottlenecks, forested hills rise to form a V, leaving a corridor of open ground only about 150 metres wide, filled with private homes.”

The gap is the narrow strip left between forested hills; the passage calls it a corridor of open ground about 150 metres wide.