Their beak and tongue, black comb and wattles; even their meat, bones and organs appear black. The blood of the Ayam Cemani is normally colored.[3] The birds' black color occurs as a result of excess pigmentation of the tissues, caused by a genetic condition known as fibromelanosis.[4] This gene is also found in some other black fowl breeds.[5][6] The roosters weigh 2–2.5 kg and the hens from 1.5–2 kg. The hens lay cream-colored eggs with a slight pink tint, although they are poor setters and rarely hatch their own brood.