The Ibises have long down curved bills, and usually feed as a group, probing mud for food items, usually crustaceans. Most species nest in trees, often with spoonbills or herons. The Flamingos often stand on one leg, the other tucked beneath the body. Standing on one leg allow the birds to conserve more body heat, as they spend a significant amount of time wading in cold water. As well as standing in the water, flamingos may stamp their webbed feet in the mud to stir up food from the bottom. The Spoonbills have large, flat, spatulate bills and feed by wading through shallow water, sweeping the partly-opened bill from side to side. The moment any small aquatic creature touches the inside of the bill [an insect, crustacean, or tiny fish] it is snapped shut. Spoonbills generally prefer fresh water to salt but are found in both environments. They need to feed many hours each day.