Though storks are considered to be largely silent birds, most species perform some variety of a bill-clattering display. This display reaches its most advanced form in the White Stork. They begin by throwing their heads straight back to create an amplifying resonance box in the gular pouch of the lower neck. The European subspecies of the White Stork breeds in several discontinuous populations across much of Europe, the Middle East and west-central Asia. A very small population breeds in extreme southern Africa in Cape Province, South Africa.
Storks are large birds that rely heavily on energy efficient soaring flight during migration.
Soaring requires the presence of thermal air currents that are not found over water. White Storks are therefore reluctant to fly across large bodies of water such as the Mediterranean Sea to reach their wintering grounds in tropical Africa. They solve this problem by having the bulk of the European population split into two distinct migratory routes. Western birds cross the Mediterranean at the Straits of Gibraltar, while most of the eastern birds cross the Bosporus and circle around the Mediterranean through the Middle East. Migration is highly synchronized and flocks contain as many as 11,000 individuals.