Some mammals, like bats, can fly. Other mammals, like whales, can swim. Most mammals are born alive. Their babies drink milk from their mother's body. Mammals breathe in air through their lungs.
Mammals are warm-blooded.
Their body temperature always stays the same. Birds Birds have wings and feathers. Birds can be many different colors. Feathers help keep birds warm and dry. Most birds can fly using their wings and feathers, but a few cannot fly.