Magnetic Navigation By Birds

Careful tests with homing pigeons and other birds displaying the ability to judge direction show that the birds are affected by changing magnetic fields. Small coils placed near the birds' heads to create unnatural magnetic fields there do disturb the ability of pigeons to find home. Magnetic storms do the same. If birds are released at places where the earth's magnetic field is anomalously strong, their homing ability is entirely disrupted.

A possible reason why birds can sense the earth's magnetic field and perhaps use it for navigation is given by Charles Walcott and co-authors in the 7 September 1979 issue of Science magazine. Dissecting a number of pigeons, these scientists found the equivalent of a compass needle in each pigeon's head.

Next to, or essentially in, each pigeon skull, they located a tiny piece of tissue 1 mm by 2 mm (about 1/16 in by 1/8 in) that was somewhat magnetic. Searches inside this tissue with an electron microscope revealed the presence of more than ten million tiny crystals each four times as long as wide. Other tests demonstrated that these crystals were magnetite, the iron-oxygen compound of which compass needles are made.

As yet, it is not proven that the millions of minuscule magnetite "compass needles" in each homing pigeon's head are used for navigation, but it seems likely that they are. These multiple compass needles are so tiny that they could readily oscillate in a rapidly-changing magnetic field such as might accompany electrical storms, earthquakes and also displays of northern lights.

So here also is a possible explanation of why birds sometimes seem to sense impending geophysical events.