Effect of pinealectomy and photoperiodism in the reproduction of indian weaver birds, <i>Ploceus philippinus</i>

Abstract

Abstract Indian weaver birds, Ploceus philippinus , are seasonal breeders and breed during June to August. Exposure of the adult male birds to long photoperiod (18L‐6D) during their nonbreeding period (November‐December), causes gonadal development and external changes (plumage and bill colour) characteristic of the breeding season, to occur a few months earlier than normal. Pinealectomy in winter also caused precocious sexual recrudescence. A combination of pinealectomy and long photoperiod accelerated the onset of the reproductive state more than either treatment alone. A short photoperiod (9L‐15D) which is normally nonstimulatory becomes stimulatory in pinealectomised birds which go into the breeding phase under this photoperiod within a few months of constant exposure. In the juvenile birds, which normally start breeding in the second year of life, precocious gonadal development and breeding can be induced by exposure to long day length and/or pinealectomy when they are only one year old. It seems that pineal in these birds inhibits early gonadal growth in the adults and delays the onset of puberty in juveniles under natural day length.