Storks arrive in March and depart in late August. They spend the winter in Africa but return each year, preferably to the same nest. They take advantage of thermals (rising columns of warm air) to cross long distance with minimal effort. Since thermals form above dry land, storks avoid crossing the open sea and prefer the routes across the Straits of Gibraltar or the Bosphorus. There are approximately 2500 nesting pairs in Greece. They lay 3-5 eggs that hatch after a month, while the young birds take their first flight after 9-10 weeks. Both parents contribute to their upbringing and supply them with a carnivorous diet of insects, worms, snakes, lizards, frogs, and small rodents. They are voracious eaters and hunters with storks having being observed catching 30 locusts per minute.