Contributions of bird studies to biology.

Birds are widely distributed, highly diversified, and exhibit behavior and social organizations equal in complexity to mammals, yet they are generally more conspicuous and approachable in natural environments. These attributes make birds excellent subjects in many areas of biological research. The topics in which studies on birds have figured prominently include the mechanisms of species formation, the regulation of the distribution and abundance of animals, the effects of the environment on behavior and physiology, the biological and evolutionary significance of variations in social organizations, the encoding of information in animal communication, the sensory basis for migration and navigation, the effects of hormones on nerve cells and behavior, the ontogeny of brain and behavior, and the structure and function of the vertebrate brain. The outstanding record of avian research suggests that birds will continue to provide important models for developing and testing new ideas in various fields of biology.