A long term investigation was made on the importance of thyroxine and prolactin in the reproduction of a tropical wild bird, spotted munia, Lonchura punctulata. Different doses of thyroxine i.m. (0.5, 1.0 and 2.0 microg; 0.56, 1.12 and 2.24 n mol Sodium salt, Sigma) per day/bird were administered in 0.1 ml of 0.9% alkaline NaCl per day per bird. Similarly various doses of prolactin (1.0, 2.0,. and 4.0 i.u.) were given per day/bird in 0.1 ml of 0.9% alkaline NaCl. Almost normal testicular cycle

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... as observed in vehicle treated birds. All three doses of thyroxine suppressed the cycle almost completely indicating a gonado- inhibitory nature of the hormone. Testicular development in all three prolactin treated groups was also inhibited in peak breeding time which indicates the antigonadal nature of this hormone in the reproduction of this bird.