文档介绍：课时提升作业
十四　必修3　 Unit 4　Astronomy: the science of the stars
(限时35分钟)
Ⅰ. 阅读理解
A
(2021·衡阳模拟)
By the time Robert Porter Allen was born in 1905, the whooping crane(鸣鹤)was already in trouble. The beautiful bird was once commonly found across North America. By 1941, the whooping crane population had dwindled to the double digits. The tallest species in North America was critically endangered.
In the 1940s, the remaining cranes migrated(迁徙) every year from the Gulf Coast of Texas to somewhere in the north of Canada to breed(繁殖). The conservation community didn’t know where the birds went. The wetlands where they used to spend winters were growing rarer and rarer as the tiny, non-migrating group of whooping cranes was alive in Louisiana in 1941, but the group had disappeared by the time Allen started his research.
In 1942, Allen undertook the whooping crane project over the next three years. He did almost constant field work that took him from Texas up the cranes’ migration route to Nebraska, and on into Saskatchewan in search of the nesting ground of the birds.
Studying the bird in its breeding habitat and seeing how many birds were born would allow conservationists to understand how to help the birds on their journey. But finding the whooping crane’s nesting site meant difficult and fruitless air searches over northern Canada.
In 1952, Allen wrote a report on the whooping crane. The report was a warning call to the conservation community: only 33 migratory “whoopers” remained, and their nesting site still hadn’t been found. Two years later, the whooping cranes’ breeding grounds in Canada’s Wood Buffalo National Park were finally found, and Allen headed north to study them first-hand—an “incredibly difficult journey”, in Sprunt’s words. Allen’s work laid the groundwork for conservationists to save the birds.
Their efforts paid off as the numbers reached 57 by 1970 and 214 by 2005. Today, the whooping crane is still listed a