When flying, Common Cranes (Grus grus) regularly break formation to gain altitude when crossing warm air updrafts. They can thus climb up to 5,000 metres. The rate of their wing strokes is about 3 per second, with hovering periods that give an impression of flexibility. Cranes flap their wings continuously in bad weather, over the sea, and at night. The group emits loud and regular calls in flight that allow each bird to stay in contact with each other.