The annual gonadal cycle of the Black Kite indicated that during the breeding season the birds gained body weight. In the sexually active phase the right testis was larger than the left. All stages of spermatogenesis were observed during the the sexually active phase. Retrogression of the testis occurred during May and June and testes were smallest during the inactive phase. Recrudescence occurred in November when the testis begins to increase in size. During the active phase the single left ovary attained maximum size. The retrogressive phase occurred during May and June and the ovaries desreased in size and weight. Ovarian size was smlalest during the quiescent phase, from July until October. Maturation of ovastarted during the recrudescent phase which occurred in November.
Yamashina Institute for Ornitology