试题出自试卷《北京航空航天大学2014年考博英语真题》

Recent research from animal behaviorists suggests that “ as the crow flies ” should no longer be taken to mean “the shortest distance between two points. ” Zoologists at Oxford University,（1）conducted an eighteen-month （2） of homing pigeons, have concluded that under some circum- stances ,pigeons follow （3）visual landmarks to find their way home （4） than taking the shor- test, most direct route. （5） for their ability to navigate long distances, homing pigeons use the （6） of the sun and stars, their inbuilt compasses，and perhaps also their sense of smell to direct their flight over long（7） or on a journey for the first time. （8），different factors appear to affect a pigeon’s navigation （9） it is released close to its（10） Animal behaviorists reached this （11）after attaching small global positioning devices to the backs of pigeons and releasing them a few miles from their home. These devices enabled the scientists to（12）the precise location of each pigeon ev- ery second of （13） flight. Each pigeon was tracked for approximately twenty flights from the （14）point. For the first several flights，each bird’s path（15）significantly from the paths it had taken （16）Subsequently，（17），the bird would tend to follow the same path, （18） after flight, even though that path was not always the most direct route home. The scientists concluded that pigeons use a （19） of familiar visual landmarks to find their way when they are near their home rather than rel- ying primarily on compass navigation. Major highways are one （20）landmark. Almost comically, some of the pigeons followed the path of a major highway they could see below them, turning where the road turned, and even following the circular path of the exit ramps.