Actually, I haven't created this cross yet. My Biel girls haven't been laying and I kept my two Biel cockerels away from the NNs for the time being while I focused on maintaining a pure line of NN with primarily one cockerel's genetic material, the one I recently butchered.
The Biels themselves are a gorgeous and very lovable breed, with cockerels that are as friendly as pullets and tolerant of other cockerels....but they're not very heat tolerant. I actually installed portable A/C units in my chicken cabin primarily to keep the Biels from overheating this past summer, and I culled all of the cockerels that struggled the most with the heat. In fact, the only bird I lost to the summer heat was a large Biel cockerel.
The three pullets and two cockerels I still have are the most heat tolerant and have adapted sufficiently to be able to endure up to about 95 degrees as long as they have access to shade, cool water, and preferably a stream of water + mud to stand in. The lack of heat tolerance is actually one of the reasons I want to cross this breed with NNs. The other reason is for improved productivity. One of my Biel pullets began laying at 24 weeks, laid for several weeks, and has since stopped laying for nearly three weeks now. The other two girls haven't begun laying at all, and they're now 32 weeks old. They're a nice large breed, with my cockerels currently weighing 9 lbs and 8.4 lbs respectively at 32 weeks, and one of my cockerels is so sweet and friendly with me that he routinely jumps up onto my lap to nestle in for snuggles and to nap. Both of my boys are very "gentlemanly" with the girls and take very good care of them. They hearty eaters though. You have to be prepared for that.
If you want any stats on the breed I'd be happy to share what I have. Like you I tend to chart, graph and photograph almost everything.
But...no, I really don't know for certain. That's the fun of this breed for me...watching how they feather out because each on has it's own unique look.
