Common Cranes (Grus grus) are difficult to miss. When flying, they make trumpeting screams every 10 seconds which can be heard for miles around. During courtship, they make small screams while hopping with their wings outstretched. The exceptional power of the crane’s scream is owed to its hollow sternum in which the trachea loops, thus acting as a sounding board. At night, cranes gather in marshy areas, sleeping with their heads under their wings. At the slightest noise, the lookouts sound the general alarm.