Turtle dove Streptopelia turtur, adult perched in tree top, Fowlmere RSPB reserve,

Understanding migration

Migration was a mystery to humans for a long time.

Migration throughout history

It is only in the last hundred years or so that we have really begun to understand migration. Before then, people had some pretty strange ideas. 

But even with all the advantages of modern technology, we still have lots to learn. 

Ancient books show how people in early times noted the comings and goings of birds. In the Iliad, written in the 8th century BC, the Greek poet Homer described the Trojan army as being ‘like the cranes which flee from the coming winter and sudden rain’. 

In The Bible, the prophet Jeremiah says: ‘Yea, the stork in the heaven knoweth her appointed times; and the turtle (turtle dove) and the crane and the swallow observe the time of their coming’ (Jeremiah 8: 7). Thousands of years ago, migratory birds were an important source of food. No wonder people noticed when they disappeared!

Ancient theories and strange stories

The ancient Greek scientist and philosopher Aristotle made the first serious attempt to explain migration.

He even spotted that birds get fatter while migrating. But he didn’t get everything right. For example, he thought that many birds, including swallows, storks and kites, hibernated in trees for winter. He even believed in transmogrification, which is the idea that some species magically change into others – such as redstarts becoming robins for winter.

Some early explanations for migration seem pretty bizarre today. When a swallow was found dead in a reedbed, people thought this proved that swallows hibernated in the mud at the bottom of ponds. Believe it or not, people even thought that barnacle geese hatched from barnacles. 

Perhaps this was because of the colour of barnacles, or because their 'feet' (called cirri) look a little like feathers. In fact, barnacle geese migrate to Greenland to breed, but it was not until 1891 that a European scientist arrived there and actually saw one of their nests. 

All around the world, people had their own ideas. The Cree Indians of North America thought that small birds, such as warblers, migrated on the backs of larger ones, such as sandhill cranes.

Changing times

OK, so some of these early stories sound ridiculous. But don't forget that the first scientists had none of our modern equipment.

There were no binoculars or bird books, let alone computers or satellites. They didn’t even have accurate maps of the world to work out where the birds might be going. And isn’t the real truth – that tiny birds fly thousands of miles from one continent to another – even more unbelievable?

Barnacle Goose feeding flock, Loch Gruinart RSPB reserve, Islay, Scotland