Variations in plasma corticosterone, estrone, estradiol-17 beta, and progesterone concentrations with forced renesting, molt, and body weight of captive female American kestrels.
Corticosterone, progesterone, estradiol-17 beta, and estrone were quantified in plasma collected weekly (April-September) from renesting and nonlaying female American kestrels (Falco sparverius) paired with males in captivity. Hormone levels and body weights for laying females were maximal during courtship and egg-laying periods, while those for non-layers showed no such distinct peaks. This demonstrated that these profiles were not controlled solely by photoperiod. Plasma corticosterone levels were elevated in all females during August and September when kestrels are preparing for migration. For laying females, body weight was positively correlated with plasma estrogen levels. A low spring body weight gain, and not stress, may have prevented the females from breeding in captivity. The photoperiodic control of molt did not appear to be mediated directly by the hormones studied, since there were no changes in hormone levels associated with the onset of molt.
D000818:Animals; D001717:Birds / Q000097:blood* / Q000502:physiology; D001835:Body Weight; D003345:Corticosterone / Q000097:blood; D004970:Estrone / Q000097:blood; D005241:Feathers / Q000502:physiology*; D005260:Female; D012739:Gonadal Steroid Hormones / Q000097:blood*; D008297:Male; D009425:Nesting Behavior / Q000502:physiology*; D009994:Osmolar Concentration; D011374:Progesterone / Q000097:blood; D012098:Reproduction; D012621:Seasons
D012739:Gonadal Steroid Hormones; D004970:Estrone; D011374:Progesterone; D003345:Corticosterone