CHANGES IN OVARIAN GROWTH AND PLASMA ESTRADIOL CONCENTRATION IN RESPONSE TO PHOTOPERIODIC TRANSFERS IN BLACKHEADED BUNTING

Photosensitive female Blackheaded buntings when exposed to long day (1 5L/9D) and continuous light (24L/OD) for longer duration showed an inc rease followed by decrease in ovarian weight and plasma estradiol conc entration and thus they become photorefractory. While the birds transf erred on continuous dark phase (scoto phase) for 30 days shown to have effective to terminate the photorefractoriness and thus maintained th eir photosensitivity. The present study reveals that it is the time of exposure of light which plays an important role in maintenance of pho tosensitivity and photorefractoriness in buntings and thus suggests th e presence of an endogenous circadian component which may operate thei r in.