题型：任务型阅读 题类：常考题 难易度：普通
山东省潍坊市2020届高三上学期英语期末考试试卷
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. 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.
Nighttime migrators include sparrows, warblers, flycatchers, thrushes, orioles and cuckoos. Most of them don't live in vast open places. 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. 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.
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.
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