For thousands of years, birds have been domesticated by humans. In this article, the author argues the effects of domestication on the physical structures, cognition, and behavior of certain bird species, especially parrots. The author describes further details of several aspects of domestication. Animals can have sufficient food and a secure environment under domestication; therefore, the cognition and behavior of captive animals may be affected by the condition. Breeders often select individual animals that have a preferable trait. Artificial selection may change the frequency of an existing gene variant in a population, whereas natural and sexual selection may be inhibited under domestication. Artificial selection may unintentionally introduce changes in cognition and behavior to a population as a by-product of the intentional selection of certain other traits. Furthermore, the author discusses that certain interesting behaviors of domesticated animals may not be caused by the domestication itself, but by relationship to humans or by a meeting with human cultures. For example, the author focuses on recent studies reporting responses by birds to the melodies of man-made music.
