Birds' Techniques for Gliding
It requires a great deal of energy to fly. However, birds are small creatures and the energy they can store in their bodies is limited. Birds obtain most of the energy they need by means of applying special flying techniques. Gliding in the air without flapping their wings is one of the techniques that they use most. For example, vultures employ a special method based on rising heat currents in order to glide at a convenient altitude. Gliding from one current to another, they can cover a vast area in a day.
Migratory birds, too, make use of gliding techniques to save energy. Storks, for example, use heat currents to fly during migration. White storks of central Europe migrate to spend winter in Africa and cover a distance of about 7,000 kilometers (4,350 miles). If they were to flap their wings all the way to their destination, they would have to take four breaks during the journey. Yet white storks complete their journey in three weeks by gliding between the heat currents for 6-7 hours a day and thus saving most of their energy.
Since the sea warms up more slowly than the land, there are no heat currents over the sea. For this reason, migratory birds prefer to migrate over land instead of making long sea journeys. You may have seen flocks of storks that cover the sky at certain times of the year. That is because storks, too, prefer to migrate over land. You may not be aware of the fact that there is no warm air over the sea, but storks know it very well.
On the other hand, albatrosses, seagulls and other sea birds save energy by using air currents caused by high waves. These sea birds that fly over the waves benefit from the lift force of the air that turns upwards.
As seen in the examples given here, all birds know which techniques they will use, where they will go and which route they will take. No confusion arises for those that fly by using warm air currents and those that fly by using air currents caused by the waves. This is because Allah inspires every creature with the knowledge it needs. In the Qur'an, Allah points out birds' movements in the air and states:
Do you not see that everyone in the heavens and earth glorifies Allah, as do the birds with their outspread wings? Each one knows its prayer and glorification. Allah knows what they do. (Surat an-Nur: 41)