Hormones and reproduction in birds:: Influence of environmental and social factors

In the first part of this article a review of the physiological mechanisms responsible for sexual reproduction and the organizational and activational effects of hormones on sexual behavior in birds is presented. In the second part, the main effects of a number of environmental and social factors on the onset of sexual behavior in birds are discussed. The role of photoperiod on sexual behavior is examined by presenting the most relevant of the extensive literature on the subject. Other environmental factors such as temperature, humidity, and resource availability are also reviewed. Finally, research evaluating the role of social cues on the onset of sexual behavior is presented in detail. Suggestions for future research and an analysis of the most relevant problems are discussed throughout the article and then briefly summarized in the last section.