Usually, birds start migrating towards other areas when they perceive the tailwind to be favorable. However, once they start their migration journey, nothing can stop them, except extremely bad weather. Many birds prefer to fly at a higher altitude while migrating. This is because winds usually prevail at higher altitudes and at the same time, the cold temperature at these altitudes helps them in diffusing the body heat, which is generated by their flight muscles. The timing of the migration is usually a mixture of internal and external stimulus.
Migrating birds start on a journey when they feel that they have put on
enough fat to provide them energy throughout the journey. Then, the
tendency to aggregate into flocks is another determinant of the time of
migration. Even after the flock, which has to fly together, has
gathered, the birds keep on feeding till the weather conditions become
favorable. Thus, apart from the internal clock of the birds and their
flock, it is also the availability of food and the weather conditions
that play a role in the determination of the time of migration.Migratory Birds Coming to India in Winter Season





