Abstract
Groups of photosensitive male Crested Buntings were exposed to short days (8L : 16D), long days (15L : 9D), and constant illumination (LL) for 60, 85 and 105 days, respectively. Periodic laparotomies during the treatments indicated that the testes were stimulated in the birds in 15L : 9D and LL, but not in 8L : 16D. Also, testicular growth in LL was followed by rapid involution after 75 days, indicating‘onset’ of the photo-refractoriness. However, except a slight decline (P<0.05) in weight of the birds in LL at the end (day 105), there was no significant difference between initial and periodically observed weights in any of the treatments. The results suggest that the Crested Bunting is a photosensitive bird which might be using daily photoperiods in control of its seasonal responses in nature, and has a post-reproductive refractory period in its annual gonadal cycle.
