Eurasian kestrel

The kestrel is a small diurnal bird of prey, widely spread also in urban areas. Like other raptors, it performs often the so-called "holy spirit" flight, which allows it to stay hovering in the air to monitor the underlying ground, looking for potential prey. To stand still in place it must simultaneously move the wings and keep its fantail open to counter the thrust forward, taking a very oblique position reminiscent of the typical representation of the Holy Spirit in classical iconography: a motionless dove with outstretched wings. This technique is very expensive from an energy viewpoint but likely allows to better define the position, distance and movement of preys. It is in fact adopted by other birds as well, such as terns and kingfishers when they hunt their prey in the water.