Birds are a group of warm-blooded vertebrates that have tw0 legs, two wings, feathers, toothless beaks, and a strong lightweight skeleton.  They typically build a nest and lay hard-shelled eggs in the trees and on land.  It is estimated that there are over 800 species of wild birds in North America.  Scientists estimate that there are between 9,000 and 11,000 species of wild birds in the world today!