Origins from Ayam Bekisar
It is very likely that the ayam Cemani are derived from the "ayam Bekisar". Ayam Bekisar is the Indonesian name given for a 1st generation hybrid between the male green jungle-fowl (Gallus varius) and female domesticated chicken or red jungle fowl (Gallus gallus). Ayam Bekisar, pertains specifically to the male offspring from the cross of the red and green jungle-fowl species. The female hybrids are infertile and indeed many 1st generation males from these crosses are often also infertile.
The Ayam Bekisar hybrids are much valued by Indonesians and Oceanic cultures for their crowing. They were originally used as a form of forgone by ancient Austronesian boat cultures. They served as hardy canoe mascots where their distinctive and often unique crows could be heard from several miles. Their deeper crow are sometimes described as a roar and can be heard over long distances and in poor weather. These allowed ancient mariners to remain in vocal distance and even identify the vessel by the different crowing voices, some are said to be almost human in quality.