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 during the day,and then switch to the star navigation by night.
One study shows that the homing pigeon relies on its perception of the Earth’s magnetic fields for its orientation, and there are indications that various other animals,from insects to mollusks,can also make use of magnetic compasses.
It is,of course,extremely useful for a migrating bird to be able to switch to a magnetic compass when clouds blot out the Sun; otherwise it would just have to land and wait for the Sun to emerge again.
Even with the Sun or stars to steer by, the problems of navigation are more intricate than they might seem at first.
For instance, a forager bee that has found a rich source of nectar and pollen makes a beeline for its hive to report.
A naturalist has discovered that the scout bee delivers her report through a complicated “dance” in the hive, in which she tells hive mates not only how far away the food is,but also what direction to fly with respect to the Sun.
But the Sun does not stay put all day.
As the workers start out to gather delectable food,the Sun may already have changed its position in the sky somewhat.
In later trip during the day, the Sun will move farther and farther toward the west.
Yet the worker bees seem to have no trouble at all in locating the food source.
Their inner clocks tell them how to compensate for the Sun’s constant motion,and they change their course correspondingly.