Question

    While plenty of birds-such as swallows, hawks and hummingbirds-migrate (迁徙) during the day, the majority of land birds travel at night.

Migration at night has at least three advantages. 1. Secondly, the air in the atmosphere is usually more stable than during the day. Lastly the air is cooler at night. A migrating bird produces a huge amount of heat that needs to be released. Most of the heat is lost from the    unfeathered legs. 2.

Nighttime migrators include sparrows, warblers, flycatchers, thrushes, orioles and cuckoos. Most of them don't live in vast open places.3.They aren't the best fliers, so they need the thick coverage to avoid enemies.

But flying at night is becoming more dangerous than it used to be.4.A well-lit high- rise can kill hundreds of migrating birds in a single night, an issue that has started to attract more public concern. In cities like New York, Chicago and Houston, some skyscrapers and other landmarks now have "lights out" programs during key bird migration times in the fall and spring.

5.A protein called cryptochrome, which is sensitive to blue light ₉ is thought to be the key to making this happen. Cryptochromes from migratory birds have evolved to require less light and to allow their recognition of blue light to sense and respond to magnetic fields (磁场).

A. Instead, they live in the woods and other sheltered habitats.

B. Birds need the heat to keep warm and maintain a good state.

C. Birds do not have to worry about attacks from dangerous birds.

D. Only when there is enough light can they get signals to migrate.

E. Migrating birds use Earth's magnetic field to help them navigate.

F. Lights on buildings and towers confuse birds, causing them to crash.

G. The colder the air temperature is, the more quickly that heat can be released.

Answer

1.C

2.G

3.A

4.F

5.E

【解析】

这是一篇说明文。文章主要说明了鸟类夜间迁徙的三个好处，以及夜间迁徙动物的居住地和人类建筑物上的灯光对夜间飞行的鸟类的影响。

1.结合上文Migration at night has at least three advantages.(夜间迁移至少有三个好处)可推知，本句是在说明鸟类夜间迁徙的好处，如不必担心来自危险鸟类的攻击。故C选项“鸟类不必担心来自危险鸟类的攻击。”符合上下文语境，故选C。

2.结合上文A migrating bird produces a huge amount of heat that needs to be released. Most of the heat is lost from the unfeathered legs.(候鸟会释放出大量的热量。大部分的热量是从没有羽毛的腿上流失的)可知本句是在说明夜间因为温度更低，更有助于鸟类热量释放得快。故G选项“空气温度越低，热量释放得越快。”符合上下文语境，故选G。

3.根据后文They aren't the best fliers, so they need the thick coverage to avoid enemies.(他们不是最好的飞行员，所以他们需要厚厚的覆盖物来躲避敌人)可知，夜间迁徙动物生活在森林和其他受保护的栖息地。故A选项“相反，它们生活在森林和其他受保护的栖息地。”符合上下文语境，故选A。

4.根据下文A well-lit high- rise can kill hundreds of migrating birds in a single night, an issue that has started to attract more public concern.(一幢照明良好的高层建筑可能在一夜之间杀死数百只候鸟，这一问题已开始引起越来越多的公众关注)可推知，本句是在说明建筑物上的灯光会迷惑鸟类，导致他们坠落。故F选项“建筑物和高塔上的灯光迷惑了鸟类，导致它们坠落。”符合上下文语境，故选F。

5.根据下文Cryptochromes from migratory birds have evolved to require less light and to allow their recognition of blue light to sense and respond to magnetic fields.(候鸟身上的隐色已经进化到需要更少的光，并允许它们识别蓝光来感知和响应磁场)可知，本句是在说明候鸟会利用地球的磁场来帮助导航。故E选项“候鸟利用地球磁场帮助它们导航。”符合上下文语境，故选E。