The Phoenicopteridae family, the only family in the order Phoenicopteriformes, contains the flamingos and their extinct relatives. All extant species, two from the Palearctic and four from the Nearctic, belong to the genus Phoenicopterus. Flamingos are long-legged, long-necked wading birds that are believed to have evolved from swimming ancestors. They filter-feed on brine shrimp and blue-green algae. Their beaks are specially adapted to separate mud and silt from the food they eat, 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. Flamingos live and nest colonially, sometimes in large numbers. Adult birds are generally pink or red in colour, the pigment deriving from their food supply, and are frequently found in ornamental bird collections