Bird Migration Theory

Most birds are believed to migrate seasonally.

Hibernation theory

●   It was believed that birds hibernated underwater or buried themselves in  .

●   This theory was later disproved by experiments on caged birds.

Transmutation theory

●   Aristotle believed birds changed from one species into another in summer and winter.

        –  In autumn he observed that redstarts experience the loss of  and thought they then turned into robins.

        –  Aristotle's assumptions were logical because the two species of birds had a similar  .

17th century

●   Charles Morton popularised the idea that birds fly to the  in winter.

Scientific developments

●   In 1822, a stork was killed in Germany which had an African spear in its  .

        –  previously there had been no  that storks migrate to Africa

●   Little was known about the  and journeys of migrating birds until the practice of ringing was established.

        –  It was thought large birds carried small birds on some journeys because they were considered incapable of travelling across huge  .

        –  Ringing depended on what is called the  ' ' of dead birds.

●   In 1931, the first  to show the migration of European birds was printed.