Annual testicular cycle in captive budgerigars (Melopsittacus undulatus)



Captive male budgerigars housed as a homosexual group, with a constant daily light period of 14 h/24 h, visually isolated but in vocal contact with other budgerigars of both sexes, showed some gonadal structural changes throughout the year. Testicular regression was not as marked as that shown in wild, non-breeding budgerigars subjected to natural daylength changes. Production of spermatozoa occurred only four times during the year with alternate periods of sexual inactivity. During the latter, the body weight decreased, the cere colour changed to a pale blue and the birds moulted more heavily.