词数：323

　　Passenger pigeons(旅鸽)once flew over much of the United States in unbelievable numbers.Written accounts from the 18th and 19th centuries described flocks(群)so large that they darkened the sky for hours.

　　It was calculated that when its population reached its highest point，there were more than 3 billion passenger pigeonsa number equal to 24 to 40 percent of the total bird population in the United States，making it perhaps the most abundant bird in the world.Even as late as 1870 when their numbers had already become smaller，a flock believed to be 1 mile wide and 320 miles (about 515 kilometers) long was seen near Cincinnati.

　　Sadly，the abundance of passenger pigeons may have been their undoing．Where the birds were most abundant，people believed there was an ever－lasting supply and killed them by the thousands.Commercial hunters attracted them to small clearings with grain，waited until pigeons had settled to feed，then threw large nets over them，taking hundreds at a time.The birds were shipped to large cities and sold in restaurants.

　　By the closing decades of the 19th century，the hardwood forests where passenger pigeons nested had been damaged by Americans’ need for wood，which scattered(驱散)the flocks and forced the birds to go farther north，where cold temperatures and spring storms contributed to their decline.Soon the great flocks were gone，never to be seen again.

【2017届高考英语一轮复习AB分类练：专题11 阅读理解（全国通用含解析）】相关文章：

★ 2017届高考英语二轮复习大题冲关秘籍完形填空之夹叙夹议文：考纲分析（含解析）

★ 2017高考四川省广安市英语阅读理解一轮系列训练：9（含解析）

★ 湖南省汝城二中2014届高考英语一轮复习阅读训练 (43)

★ 【北师大版】2014届高考英语一轮复习指导课时作业：Unit 9 B卷 Word版含解析

★ 2014高考英语（新人教版）一轮基础训练（15）A、B卷（附答案或解析）

★ 湖南省岳阳市2014高考英语一轮单项选择训练题（5）及答案

★ 【人教版】2014届高考英语一轮复习指导考点针对练：选修7 unit2《Robots》

★ （安徽专用）2014届高考英语一轮复习方案 作业手册（10）模块4 《Unit 10 Money》（含解析） 北师大版必修1

★ 浙江省湖州市2014高考英语阅读理解一轮（暑假）精炼（10）含答案

★ 备战2016年高考英语第一轮复习的七大方法