Without the magnets on their heads, they could find their way home in any weather.

The magnets on their heads were responsible for that.

With the magnets mounted on their heads, they were unable to find their way home.

The earth is like a ball with a big magnet in it.

A magnet attracts iron.

Compass needles point to the north.

When we put magnets on the pigeon's heads, what was the reaction?

In other words, the field of the magnet is near the pigeon's head.

The magnets, of course, have a magnetic field around them.

Keeton put magnets on the heads of his pigeons.

If you float a one yen coin on water and move a magnet slowly towards it then the coin will approach the magnet.

This is a horseshoe magnet.