..All the storks of the whole country will meet together, and the autumn manoevering begins, when you must be able to fly well. That is of the greatest importance; for whichever of you does not fly properly, the general will pierce through with his beak, and kill;- so take care that you attend to the exercising when it begins

a. Preparation

In 490 BC an Athenian messenger, Pheidippides, ran 26 miles from the Greek village of Marathon to Athens. His task was to tell the people of Athens of the Greek victory over the Persians. Pheidippides just managed to deliver the news before he collapsed and died. Today people run marathons the world over. The crucial difference is that, today, people prepare months in advance. Marathon training programmes are around 20 weeks long: twenty weeks of preparation to run 26.2 miles.

In the bird world the arctic tern holds the long-distance record, migrating up to 22,000 miles from the Arctic to the Antarctic and back again each year. In order to fly these distances, birds need to make dramatic preparations. This section looks at how birds effectively reinvent themselves for the migration journey.

Evolution has been preparing migrants for millions of years by favouring characteristics for long distance flight. Preparations for migration continue throughout a bird's development. Each year before the journey begins, these preparations become more intense.

i. Ancestral adaptation for migration

For almost as long as birds have been in existence, they have been migrating. The oldest fossil bird, Archaeopteryx, lived on the Earth 140 million years ago. Another, slightly later, specimen from the Cretaceous period, Hesperornis, is thought to have migrated in order to breed. Throughout bird history, traits have been selected that increase the efficiency of flight. For instance, bird’s bones are hollow. This ‘design’ makes them light yet strong.

Migratory birds have to be particularly strong and efficient fliers to minimize the costs of flying long distances. Migrants tend to have streamlined bodies with a light build, a relatively long aerodynamic tail and pointed wings. These features, like those of a Concorde, reduce the drag forces on a bird in flight and enable it to fly faster. Migrants have particularly large breast muscles, which act as the main flight engine, making them strong fliers. Their muscles have developed to allow rapid delivery of oxygen to the tissues, helping to prevent the muscles from tiring.