For guinea fowl the males have slightly larger helmets and wattles. The easiest way to sex them is by voice though. Both males and females will make the one syllable "Chi" call but only the females can make the two syllable "Buckwheat" call. Young guineas are usually quite vocal and I hear my young females making the buckwheat call multiple times per day (starting at about a month old). If you haven't heard a particular bird make that call then it is most likely a male.
Jen
Thank you, soo much! Come to think of it, these guys do make a lot of noise in the evenings, and one does have sort of a different call from the other one. I thought for sure that would be the male--whoops!!
In regard to the cabinet incubator q, I don't think the humidity will hurt the eggs at all. The ONLY time iLve had humidity-related trouble with hatches is when I set pheasant eggs and chicken eggs together. Pheasants require a higher% humidity than chickens, I think I drowned the poor chickens(but I got the other babies out!!).