Magnetic personalities

If you strap a magnet to the head of a pigeon, it gets lost.

Not just any pigeon of course, a homing pigeon, and not just any magnet ... it has to be small enough that it doesn't physically impede the flight of the pigeon. Finally, whether it gets lost depends upon the weather; the pigeon is much more likely to not return if the weather is dull and cloudy (Walcott & Green, 1974).

Numerous studies over the last five decades have shown that pigeons can sense the earth's magnetic field and use it for orientation. The demonstration that the "hat magnet" only impaired homing on cloudy days demonstrates that orientation using magnetism is secondary to orientation using the position of the sun. It's a backup, but that doesn't make it unimportant.

I invented the term "hat magnet" (somebody had to) ... the earth's magnetic field is actually detected using things inside the pigeon's beak, and blocked using tiny magnets glued to the beak. I wanted to avoid any suggestion that the vision of the pigeon was blocked, and 'beak magnet' sounded a bit daft.

The 'things' inside the pigeon's beak that detect the earth's magnetic field, direction and polarity, are termed magnetoreceptors, and I'll describe these in more detail shortly.

But not in pigeons, in bees.

This is, after all, a site that usually focusses on bees and beekeeping.

What have magnets, the earth's magnetic field and magnetoreceptors got to do with bees?

And why should you care?