Flamingos are gregarious wading birds, usually 3 to 5 feet in height, found in both the Western and Eastern Hemispheres. There are four species in the Americas while two exist in the Old World. Flamingos live in large flocks in aquatic areas. A group of flamingos is called a "pat". Flamingos are gregarious wading birds in the genus Phoenicopterus and family Phoenicopteridae. Flamingos filter-feed on shellfish and algae. Their oddly-shaped beaks are specially adapted to separate mud and silt from the food they consume, and are uniquely used upside-down. The filtering of food items is assisted by hairy structures called lamellae which line the mandibles, and the large rough-surfaced tongue. It is the shellfish and shrimps which flamingos eat which give them their distinctive pink colour, otherwise they would be white.