Every year, many kinds of birds travel huge distances between their summer and winter homes. Some of them fly thousands of kilometers across wide oceans and empty deserts, and yet they still manage to arrive at exactly the same place year after year. For a very long time, scientists have wondered how birds are able to find their way without maps, signs, or any modern tools.
Part of the answer is that birds use the sun and the stars to guide them. During the day, they can use the position of the sun in the sky to keep flying in the right direction. At night, some birds watch the stars, just as human sailors once did, in order to stay on course. However, the sun and the stars are not always visible. On cloudy days and nights, birds still seem to know exactly which way they should go.
Scientists now believe that many birds can actually sense the Earth's magnetic field. The Earth behaves like a giant magnet, and its invisible field points toward the north and the south. Some birds appear to have tiny natural materials inside their bodies that react to this field, working almost like a built-in compass. This may allow them to find the correct direction even when they cannot see the sky at all.
Young birds also learn a great deal from experience. On their very first long journey, many of them simply follow older birds that already know the route well. Later in their lives, they remember rivers, mountains, and coastlines that they have flown over before, and they use these features as natural signposts along the way.
By combining all of these different methods, birds are able to make their amazing journeys with surprising accuracy. Even today, scientists do not fully understand every detail, and the long flights of birds remain one of the great wonders of the natural world. To learn more, researchers now attach tiny, lightweight tags to some birds, which record exactly where the birds travel during the year. The information that these tags provide is helping scientists slowly solve one of nature's oldest puzzles.
（1） 正解 2. How birds find their way without maps or tools.
第1段落に「地図や道具なしにどう道を見つけるのか長く不思議に思ってきた」とある。選択肢2。
（2） 正解 2. By watching the stars.
第2段落に「夜は星を見て進路を保つ鳥もいる」とある。選択肢2。
（3） 正解 2. Many birds can sense it and use it like a compass.
第3段落に「多くの鳥は磁場を感じ、方位磁石のように使う」とある。選択肢2。
（4） 正解 1. By following older birds and remembering landmarks.
第4段落に「年上の鳥に従い、目印を覚える」とある。選択肢1。
（5） 正解 2. They remain one of the great wonders of nature.
第5段落に「鳥の長旅は自然界の偉大な驚異の一つであり続けている」とある。選択肢2。
repair：修理する
to fix something that is broken（壊れたものを直す）
volunteer：ボランティア
a person who works without being paid（報酬をもらわずに働く人）
fertilizer：肥料
material added to soil to help plants grow（植物の生長を助けるため土に加えるもの）
refund：返金
money that is given back to you（払い戻されるお金）
distance：距離
the amount of space between two places（二つの場所の間の空間の大きさ）
compass：方位磁石
a tool that shows direction（方向を示す道具）
landmark：目印
an object that is easy to see and helps you know where you are（見つけやすく場所を知る助けになる目立つもの）
accuracy：正確さ
being correct and exact（正しく寸分たがわないこと）