Birds use many aerodynamics in their flight. They have many adaptations to easy airlift. They may be physical or behavioral adaptations.
Some bird species do flight forming a “V” shape to reduce the air friction.
Only the bird in lead at the tip of the “V” feel the friction from the air and has to spend more energy on flight.
If you observe a group of birds flying forming this type of formation you can see the bird at the tip if the V will change time to time in rotation in order to avoid only one bird being exhausted of creating the air resistant free flight to other birds of the group. This behavior clearly illustrates the relationship and mutual understanding among birds.
At ALIYA you will definitely spot this kind of flight formations of
bird sets such as cormorants and ibis.