Birds are known to use a combination of things, including landmarks, the angle of the sun, stars, odors, even the magnetic field of the earth, as they migrate.
However, scientists still do not know exactly what they use for a map and compass, let alone exactly how they use them.
A flock of birds, for example, is not just headed to a general geographical area like Central America, but to a very specific location.
How do they know when they get there?
They may have an intimate knowledge of the local area, but how they are able to navigate so precisely, even over the ocean at night, is not known.
What might seem an obvious explanation, that birds who have migrated before might lead the way, is not the answer.
Ornithologists know this because in many cases the parents bail out first before the end of the year, and the young continue to feed until they are developed enough to leave, then migrate unassisted.
It appears that birds know where they are going, though they have never been there before, because it is programmed in the genetic material.
Most of the research has been done on the compass.
For example, even on cloudy days, there is a plane of polarized light that lets birds tell where the sun is, and they derive directional information from that.
But if you are plunked down in the woods from outer space, a compass won’t help you decide where to go, and one hundred years of research on the homing pigeon still has not answered the question of how a bird carried a hundred miles in a covered box immediately orients itself and heads accurately for home.
