Effect of fifteen hours of daylength has boon studied in two species of local finches. Increase daylength in baya weaver (Ploceus philippinus) induces gonad recrudescence practically immediately but not in the avadavat (Estrilda amandava) and the gonads in this species continue to regress in size. In Estrilda amandava there is a post nuptial period of sexual negativity which seems to operate both at the gonadal and hypophysial levels.