Learning objectives: mammalian vs. avian, reproductive structural and physiological differences, ovarian and follicular structure and development, etiology and how it compares to humans, flight and its impact on reproduction. Mammalian vs. avian: reproductive structural and physiological differences, mammalian (small, enclosed organs) (two ovaries, relative to body size, the ovaries are very small. In both species, female reproduction is more complex than the male and demands more energy. Nutrition also plays a vital role in female reproduction: hormones from ovary (corpus luteum will develop and facilitate pregnancy) In mammals, the ovary has 2 roles: (dual function: follicular development, pregnancy. Most follicles will never ovulate because there is a very high selection process. Roughly in all species when they are born have a million follicles. Bird may have 500-600 ovulations in their life cycle. We run out which we call menopause. Females live long enough to run out of follicles (around the age of 50 years old).