Birdlife in Bahrain is sparse except during spring migrations and after death, when many migratory birds briefly rest in Bahrain as they travel to and from more temperate latitudes. There are many small villages and isolated areas where agriculture, relying on artesian water, is the main way of life. This fertile area contrasts starkly with the barren desert that covers much of the country. Villages largely consist of substantial flat-roofed houses made of stone or concrete, though some temporary shelters of fishermen and the poor still use branches from date palms. Over a third of Bahrain's population lives in its two largest cities, Manama and Al-Muharraq.