What is the passage mainly about?

how a very small seabird makes the longest journey of any animal (Every paragraph supports one claim made in the first paragraph: no animal travels farther in a year. The trackers and the winds are details that explain how the journey was measured and flown.)

About how far does a tern travel in one year, according to the tracking data?

about seventy thousand kilometres (The third paragraph gives the figure directly: about seventy thousand kilometres a year. Thirty is the bird's possible age in years, not a distance.)

Why do the terns curve across the ocean instead of flying straight?

A longer path with helpful winds costs them less energy than a short, hard one. (The text says they curve to catch helpful winds because fighting the wind costs energy they cannot spare. So the longer route is the cheaper one.)

In "energy they cannot spare", the word "spare" means

have extra of, and so can afford to give up (The sentence explains why the birds avoid fighting the wind. They have no energy to waste, so "cannot spare" means they have none extra to lose.)

The Tern's Long Year: Level 2 Reading Comprehension Questions

The Arctic tern is a small white seabird with a sharp red bill. It weighs about as much as an apple. Yet no animal on Earth travels farther in a year.

Each northern summer, the tern nests near the Arctic. When the cold returns, it leaves. It flies south across the Atlantic to the sea ice around Antarctica, where the southern summer is just beginning. Months later, it turns around and comes back.

Scientists once could only guess at the route. Then they fitted terns with tiny trackers, light enough for a small bird to carry. The data showed a journey of about seventy thousand kilometres a year, and a path that was not straight. The birds curved across the ocean to catch helpful winds, because fighting the wind costs energy they cannot spare.

A tern may live more than thirty years. Over such a life, its flights add up to more than two trips to the moon and back. Because it follows summer from one end of the planet to the other, it also sees more daylight than any other creature alive.

Comprehension questions