Breeding Biology of Crowned Night Heron Nyctiocorax nyctiocorax in Ali-Siyah Island, Karoon River

The current study carried out on the reproductive biology and breeding success of Crowned Night Heron Nyctiocorax nyctiocorax in Ali-Siyah island in Karoon River during 2007-2008. During the study, 30 nests were selected randomly using visits by boats. The reproductive phenology of Crowned Night Heron was started with the behaviour of nest building in March 22 and finished with last fledglings in June 19. From 91 eggs in 30 randomly selected nests, 3.03 eggs were found and the clutch size was varied from 2 to 5 eggs.  The mean of breeding success in hatching, nestling and post-nestling breeding stages were 63.73% (n=58), 49.45% (n=45), 45.05% (n=41), respectively. The total breeding success during the breeding season was measured 52.74%. Clutch size, brood size and nest parameters did non-significant effects on the breeding success. Most mortality rate occurred before the hatching stage (36.26% (n=33)) mostly due to the natural factors.