Question

Before winter arrives, many kinds of birds know that it is time to fly south. The migration (迁徙) has always made us think hard. Why do only some birds migrate? How do birds know when to go south? How do they find their way?

Some birds fly south because their food supply runs short in winter. The woodpecker (啄木鸟), for example, doesn't need to fly south because it can find food in the bark (树皮) of trees. Some birds eat grains, insects and other food that disappear in winter, so they must fly south where food can still be found. But why don't they stay in the south? Perhaps they know that if they stayed down south, they would run out of food there, too.

It is possible that birds know when winter is coming because they find that the days are getting shorter. Once they leave from the north, they use the sun as a compass. The sun is in different positions in the sky at different times of day. To use it as a guide, birds would have to know the time of day. On long flight, most birds use the stars to navigate (导航) their way.

The homing pigeon (信鸽) doesn't use the sun or the stars. Scientists believe that it uses the magnetic field (磁场) of the earth. One of the most amazing migrations is that of the tiny hummingbird (蜂鸟). It travels from Canada to Mexico—a long distance of over 3,600 kilometers.

1.It is believed that some birds fly south because ________.

A.they need food B.they like warm weather

C.they get lost D.it is just a habit

2.On long migration flights, most birds find their way with the help of _______.

A.the stars B.other birds

C.the moon D.the magnetic field

3.Which of the following is NOT true according to the passage?

A.The woodpecker usually doesn't need migration.

B.The hummingbird flies to Mexico for food.

C.Birds migrate before winter comes.

D.Birds that eat insects like staying in the south better.

Answer

1.A

2.A

3.D

【解析】

这篇短文主要讲述了鸟的迁徙。

1.

细节理解。根据文中“Some birds fly south because their food supply runs short in winter. ” 有些鸟会飞到南方，因为冬天它们的食物供应不足。可知，鸟飞到南方是因为它们需要食物。故选A。

2.

细节理解。根据文中“On long flight, most birds use the stars to navigate (导航) their way. ” 在长途飞行中，大多数鸟利用星星来导航。故选A。

3.

推理判断。根据文中“But why don't they stay in the south? Perhaps they know that if they stayed down south, they would run out of food there, too. ” 但他们为什么不留在南方呢？也许他们知道如果他们呆在南方，那里的食物也会用完。可知选项D“Birds that eat insects like staying in the south better.”说法是错误的。故选D。