What is a Bird? - From DK Find Out
Flightless birds may run or swim, but most birds have wings that can carry them through the air. Bird bones are hollow to be light enough to fly. The tail works like a rudder to steer. Look at the parts of a bird's wing and skeleton. Feathers also help keep birds warm, even if they cannot fly. The feet of different birds may be adapted for perching, running, swimming, or gripping prey. Birds have different types of beaks depending on if they eat meat, seeds, nuts, nectar, or fish.
CITATION: What Is a Bird?. n.d. Web. 2 December 2015. http://www.dkfindout.com/us/animals-and-nature/birds/what-is-bird/.