大众英语80篇背诵阅读带翻译(二十九)
"58 Animals' Compasses
Researchers have found that migrating animals use a variety of inner compasses to help them navigate. Some steer by the position of the Sun. Others navigate by the stars. Some use the Sun as their guide during the day and then switch to star navigation by night. One study shows that the homing pigeon uses the Earth's magnetic fields as a guide in finding its way home and there are indications that various other animals from insects to mollusks, can also make use of magnetic compasses. It is of course very useful for a migrating bird to be able to switch to a magnetic compass when clouds cover the Sun; otherwise it would just have to land and wait for the Sun to come out again.Even with the Sun or stars to steer by, the problems of navigation are more complicated than they might seem at first. For example, a worker honeybee that has found a rich source of nectar and pollen flies rapidly home to the hive to report. A naturalist has discovered that the bee scout delivers her report through a complicated dance in the hive, in which she tells the other workers not only how far away the food is, but also what direction to fly in relation to the Sun. But the Sun does not stay in one place all day. As the workers start out to gather the food, the Sun may already have changed its position in the sky somewhat. In later trips during the day, the Sun will seem to move farther and farther toward the west. Yet the worker bees seem to have no trouble at all in finding the food source. Their inner clocks tell them just where the Sun will be and they change their course correspondingly.动物的罗盘钻研人员已经发明迁徙性动物可以借助各种百般的体内罗盘来校正方向。有些动物借助太阳的地位分辨方向，有些则拜托星星。另有的白天使用太阳，早晨使用星星。有钻研发明信鸽以地磁场为向导来找到回家的路。另有迹象表明许良多多别的生物，从虫豸到软体动物，也能使用这种磁场罗盘。具有这种磁场罗盘，对留鸟来说固然极度有效，因为如果乌云遮日，它可以以磁场为向导继承飞翔，不然它就只好着陆，期待太阳从头出现。即便是借助太阳或星星导航，其中的学问也比它表面看起来的要庞大得多。例如，一只工蜂找到了花圃蜜园，急忙飞回蜂房报信。博物学家发明这只蜂探在蜂房里跳了一段极为庞大的舞，经由历程这段舞她不但通知别的工蜂食物有多远，并且陈说了以太阳为参照的飞翔路途。但太阳不会呆在天上不动。当蜂群动身采食时，太阳年夜概已经多少窜改了它在天空中的地位。动身得越迟，太阳就越偏西，可这好像没给探求食物源的工蜂们带来任何未便。它们体内的时钟通知他们太阳应在的地位，据此它们响应地窜改行进的方向。