The scientists have shown that migrating adult sparrows can find their way to their winter nesting grounds even after being thrown off course by thousands of miles.
The team first brought 30 sparrows to Princeton from northern Washington State,where the birds had been in the process of migrating southward from their summer breeding grounds in Alaska.Half the birds were juveniles(少年)of about three months in age that had never migrated before,while the other half were adults that had made the round trip to their wintering site in the southwestern United States at least once.
After the birds were released,they attempted to resume(重新开始)their migration,but both age groups grew disoriented(迷失方向的)quickly.
“All the birds scattered at first,” Wikelski said.“It was clear that they were turned around for a couple of days.But while the adults eventually realized they had to head southwest,the younger birds resumed flying straight southward as though they were still in Washington.”
“The adults,” said team member Richard Holland,“recovered their bearings because they possess something the younger birds do not,which is an internal map.”
“These birds need two things to know where they are and migrate effectively:a ‘map’ and a ‘compass’,”said Holland,a postdoctoral research associate in Wikelski's lab.“What we've found is that juveniles use their compass,but the adults also use their map.”
【2016届高考英语(外研版 全国)一轮复习题库:必修4Module6 Word版含答案】相关文章:
★ 湖南省汝城二中2014届高考英语一轮复习阅读训练 (9)
★ 【人教版】2014届高考英语一轮复习指导考点针对练:选修6 unit4《Global warming》
★ 贵州省贵阳市2014高考英语(新人教版)一轮阅读训练(27)附答案
★ 【北京专用】2014届高考英语一轮复习方案课时作业:必修1 Unit 4 Earthquakes
★ 四川省2016届高考英语一轮复习课时作业(32) Module 2 Fantasy Literature 外研版选修6
★ (全国通用)2014届高考英语一轮单元复习 限时强化训练七
★ 湖南省汝城二中2014届高考英语一轮复习阅读训练 (42)
★ 湖南省汝城二中2014届高考英语一轮复习阅读训练 (72)
★ 湖南省岳阳市2014高考英语一轮单项选择训练题(12)及答案
最新
2017-04-24
2017-04-24
2017-04-24
2017-04-24
2017-04-21
2017-04-21