They live almost anywhere, from tropical forests to frozen ice packs, to arid deserts and vast oceans. Some fly, others swim, and some do both. A few do neither. Birds evolved from reptiles, and a connecting link to their reptilian ancestors can sometimes be seen in their scaly legs. Unlike reptiles, however, birds are warm-blooded animals.
Birds spend most of their time foraging for food.
Beaks are also used for preening and for nest-building. Several birds, such as storks, use their beaks in courtship. Birds' nesting and breeding patterns vary greatly. Others build communal nests with each couple having a separate space. Some lay eggs without nests, and some use the nests of other species.