The amazing mysteries of swallows migration

Up close picture of a swallow bird.

In the Northern Hemisphere, country folk have always greeted the return of the swallow, a traditional harbinger of spring.

But some curious ones also wondered where they had been during their winter absence.

Some thought they had hibernated.

Others suggested that they had gone to the moon—someone calculated that they could fly there in two months.

A 16th-century Swedish archbishop claimed that swallows spent the winter underwater, huddled together at the bottom of lakes and marshes.

 His treatise even contained an illustration that depicted fishermen hauling in a net full of swallows.

 Odd as these ideas now seem, the truth turned out to be nearly as strange as fiction.

During this century ornithologists have ringed thousands of swallows.

A small, but significant, percentage of these ringed birds were located in their winter quarters.

Incredible though it seems, swallows from Britain and Russia were found wintering together thousands of miles away from home—in the extreme southeastern tip of Africa.

Some of their North American counterparts fly as far south as Argentina or Chile.

And swallows are not the only birds to make such epic journeys.

Hundreds of millions of birds from the Northern Hemisphere winter in the Southern Hemisphere.

Ornithologists were amazed to discover that a bird as small as a swallow could make a round-trip of 14,000 miles [22,500 km] before returning to the same nest the following spring.

Knowing where the swallows had gone only raised more perplexing questions.

Why do swallows migrate?

“Swallow, Why Do You Leave Your Nest?”

Swallow birds in their nests.

What makes a swallow journey to the other end of the globe?

Because of the cold or in order to find food?

Doubtless, their need for a reliable food supply is the answer rather than the onset of wintry weather, since many small birds that have difficulty surviving cold winters do not migrate.

But bird migration is not just a wandering in search of food.

Unlike human migrants, birds do not wait until times are bad before moving on.

Scientists have discovered that it is the shorter day that triggers the migratory urge.

In the autumn captive birds get restless when the daylight hours decrease.

This is so even when the effect is produced artificially and when the birds have been reared by investigators.

The caged bird even faces in the direction it instinctively knows it should take during its migratory flight.

Evidently, the urge to migrate at a specific time of the year and in a certain direction is inborn.