I ask this because i have 4 nests now. One guinea has been on hers at night since april 5th, she is not on it during the day though. One of the other nests, the guinea is on it at night and most of the day,but this just started a couple of days ago. I cracked open about 6 eggs and every one of the eggs had a white spot on the yolk. Does this mean that the eggs are fertile? And is there any way you can tell if the egg is fertile by candling or do you have to wait about 15 days to tell? I candled every one of those eggs and there are probably 80 eggs to see if I could see anything developing and the only thing I could see was a shadow, that was probably the yolk. I took out the ones that I though were clear and I cracked 6 of those and found the white spot, so I put every one them back. I was just trying to get some of the eggs out of the barn, because they busted some of them from them being stacked. I took the nasty ones out and put fresh hay under all. Then I put the eggs back like I found them. LOL.. Anyway, any information would be greatly appreciated.