Good Question. mathematically, spread out over a large number, one should get 50/50 for the sexes. The female embryo is more sensitive to the heat than the male embryo. I forget the exact temps, but if the temperature gets too high, it's possible the females may die and thus give a hatch with more males than females. That said, Marans have a thicker shell than other poultry. Some say this can make them harder to hatch than other breeds. If folk start messing with the incubator temps with that in mind, it's possible they could get the temp too high and following the thread of thought above, get more males than females. This is all subject to, and depends on how, the person deals with the accumulation of facts above. Personally, I just use a Brinsea incubator with digital auto-temp and get nice hatches with good ratios.
Karen in western PA, USA
that was on my line of thinking. these are the folks that I got my oakly incubator from when they used the old oakly their hatches were poor to say the least they've gotten a sportmans now and their hatches have leveled to what they expected. but it seemed a little off the it was only the CM's that they hatched this happened. 16 roo's out of 24 can fill a freezer pretty quick.
Black Coppers cannot be sexed by color as day olds or as chicks. Breeding for the naturally occuring traits (ie...fast and slow feathering ) that happen in males and females and are noticeable traits as chicks can be done, but it is also not 100% accurate, so the waiting game is the only way to accurately sex them. By the age of approx. 10 days to 3-4 weeks.....little cockerels combs and wattles should be screaming MALE.
The only Marans that are sexable at hatch (unless vent sexing) are Cuckoo's. The only other variety of Marans that is sexable at a very young age by feather color is the Wheaten variety.
Ok thanks for clearing that up pinkchick. That is what I have been told in the past that you cannot sex black coppers that early. As much as I'd love to know what my week olds are.....guess I'll wait a while longer. Seems like I'm always waiting on these darn chickens. Waiting for eggs to ship, eggs to hatch, old enough to sex, waiting on eggs from my girls.... Got to love it!