Bird migration

Photo: Petr Hamerník, Prague Zoo

Among the main factors responsible for migratory behaviour are climate seasonality and intraspecies competition.

Most species are not taught the migratory journey from their parents; instead it is encoded in their genetic makeup. The latest research shows that individual populations only differ by what level of this behaviour they exhibit.

WHERE

The timing of migration is no random event. The birds have internal rhythms - both daily and annual - that give them a sense of time. This internal timing is, to some extent, innate and it is only to a certain degree that it is influenced by external conditions.

NOCTURNAL MIGRANTS

Twice a year nocturnal migrants move their activities to the night.
Radar studies prove that night migratory activity begins about an hour after dark and culminates shortly before midnight.

The reason for night migration is probably lack of time (during the day the birds eat) as well as the weather conditions (flying at night saves energy).

SPEED

Birds regulate their flight speed so that the energy demands for overcoming the distances are as small as possible. The character of spring migration tends to be quite different from that of the autumn - in spring the birds are compelled to fly faster in order to reach their nesting sites on time.

ORIENTATION

How the sense of direction works in birds has not been clarified. One of the theories is that they use distinct points on the Earth’s surface, such as larger watercourses.

Birds that migrate during the day use the sun to find their way; those flying at night use the stars. The perception of magnetic fields is also important.

MIGRATION ROUTES TO AFRICA

The birds most often use three migration routes to Africa to minimise the flight across the Mediterranean or completely avoid it.

These are the south-western route (across the Iberian Peninsula and the Strait of Gibraltar), the south-eastern route (across the Balkan Peninsula and the Middle East), and the southern route (over the Apennine Peninsula, Sicily and Malta and the African continent).