Site index Introduction Birds are warm bodied creatures with wings and feathers. The body temperature of birds is generally higher than that of humans, so they seem warm to the touch. In some species such as our songbirds, the young hatch naked and helpless and must be fed and cared for by a parent bird. Others, like the chickens and their relatives, produce down-covered young that are able run about and feed themselves. They are still dependent for protection upon adult birds.
Birds range in size from thumb-sized hummingbirds to ostriches larger than a big man.
Most birds, of course, fall somewhere between these two extremes. One common bird, the American Robin is about 10 inches in length, approximately the handspan of a large man. The smallest american birds are some species of hummingbird that could nest and raise a family in the cupped palm of a child. The nearly extinct California Condor has a wing span of almost 10 feet, and the Bald Eagle spans 7 feet. Birds walk, run, hop, swim, perch, cling, fly and even dig.