American Kestrel (Falco sparverius) Science Article 12
The concentrations of maternally derived androgens in the yolks of avian eggs vary within and among clutches, but a mechanistic basis for this variation has not been elucidated. We investigated in the American kestrel, Falco sparverius, whether changes in plasma-prolactinconcentrations induced by changes in photoperiod and food supply affect yolk-androgen concentrations.
Keith W. Sockman, Hubert Schwabl, and Peter J. Sharp, Hormones and Behavior 40, 462-471 (2001)