As @chickengr indicated, humidity needs are the prevailing theory, but I also know of some people who claim that temperature requirements are different too. If you ever peruse the Biel thread you'll see that most people seem have difficulties hatching Biel eggs not matter what method they choose.
The little flock that Bellatrix ( your eventual black NN) is part of had included two fertile Biel eggs that fizzled when they were fully developed, and they were under one of my broodies. Granted, she was a first timer and not the best mother overall, but given all the problems with the eggs I just think it's a breed issue. From now on, if I want to hatch any of my Biel eggs I have one very skilled White Rock who's given me outstanding hatches and has proven to be an exceptional mother. She's the one who hatched my two Biel/NN mixes as well as Biel/Australorp, Biel/Silkie and Biel/Ameraucana mixes. The girl's good!
My Biels have never gone broody, but my Biel mixes have. I think the trait is in there somewhere, but it's a little hard to bring out in the Biels. I don't know of too many Biel owners who've gotten broody girls from the breed...at least, not here in the states.
