Photoperiodic control of seasonal reproduction in tropical weaver bird

Abstract

Experiments were performed in order to provide information on the extent of involvement of daylength, if any, in the control of seasonal breeding in the tropical weaver bird. The reproductive cycle was completely abolished in both short and long photoperiods. The cycle was suppressed in short photoperiods, and in long photoperiods gonads were maintained in a stimulated state indefinitely. These results indicated a definite photoperiodic requirement for gonadal development in the weaver bird. the photoperiodic response threshold was found to be 11 hours daily. Gonads in a period of 12L/12D exhibited cyclicity, though at a low level, indicating that a light period of 12 hours daily allows gonadal regression which is abolished in longer photoperiods. On correlating these laboratory observations with the natural reproductive cycle, it seems that the annual timing of reproduction in the weaver bird may coincide with the time in the spring when the increasing day length reaches the photoperiodic response threshold.