I've been hatching my own cuckoo eggs for several years and I've never used any higher humidity for them. My eggs are nice and dark so I really don't think it makes a difference. They're usually in with other eggs and when they're my own eggs they all hatch just fine.
It also depends on the type of incubator. Apparently, the larger type (like the Sportsmen) incubators do a much better job hatching Marans eggs. I know Bev Davis did an experiement where she used a styrofoam Hova incubator and her sportsmen at the same time, and got a much better hatch from the sportsmen.
I'm thrilled with my copper blacks! They're VERY nice specimens of the breed. I just think we got a bit unlucky with the postal handling, because others have gotten excellent hatches with them. So long as my pullet eventually lays and my roo is fertile, I'll be able to hatch more later on.
I had some problems hatching the coppers myself.
Grant it they were shipped eggs, but so far all of my eggs have been shipped and I had a tough time keeping the humidity down.
The first time I had a zero hatch I talked to the breeder who told me she keeps her humidity between 40-50 percent.
I had trouble keeping it low myself, I wasn't even adding water to the bator anymore.
After the hatch date had come and gone I candled the eggs and saw they were formed.
I cracked a couple open and it seems to me they drowned in the extra fluid in the eggs.
I ended up buying chicks and now have 11 copper marans and they are the most spritely little things.
I really love them, they look like little wind up toys when you put them down and they run across the room.
I have cuckoos that I hatched out myself from shipped eggs, got a 100 percent hatch rate, no problem.
I think the coppers definitely have different requirements.
Just my experience.
You can say that again! When it fails its so discouraging that you don't want to do it again, but when its successful you are so elated.
The thing is its so much easier to buy eggs than to buy chicks, as far as quality goes anyway.
I know you can always by hatchery chicks, and I am not saying there is anything wrong with that,but if you want a specific breed in a certain quality you usually have to go with eggs and keep your fingers crossed.