I thought I'd better update, in case anyone was wondering! Matilda (our cuckoo maran) went broody. We had 6 eggs from a breeder, and put two of our own under her as well. So she was sat on 8.
Matilda broke 2 of the 8 fairly early on. I don't know if that was from being clumsy or some instinct telling her that there was a problem.
The day before the eggs were due to hatch I found two eggs broken, both with fully formed chicks inside. I don't know if she stood on them by mistake, or if one started to hatch and she didn't understand what was happening, no idea what went on there. It was very sad The shells were smashed to bits so I think she did stand on them somehow.
We left the remaining 4 under her, but we were nervous that she was breaking them on purpose, or just massively clumsy, either way we decided to put the eggs in an incubator and give Matilda some chicks. She seemed to like them at first, but after a few hours she went off the idea of motherhood! She rejoined the flock and isn't broody anymore. We're raising the 8 chicks indoors, hoping we get 4 girls!
Once the eggs in the incubator were a week past their due date we broke them open. Three were unfertilised, they just looked like a normal egg you'd cook with. The last one had been fertilised, but hadn't developed into anything, it looked like runny custard.
So out of 8 eggs there would only have been two chicks! One of the breeders (a yellow chick) and one of our own (a black chick). I think I'll just buy chicks and hens in future, eggs are way too much drama!
The 8 chicks we bought are 2 Rhode Island Reds, 2 Vorwerks, and 4 Silkies. We already have a Cuckoo Maran, a French Blue, a Coppr Black and two Jubilee Orpingtons. We're planning on keeping a cockerel, either a Vorwerk or a Silkie as we've heard they're pretty calm. I keep reading that Rhode Island Red cockerels are aggressive so we're hoping they're girls!
The chicks vary in age by a few days either way, but they're about 4 weeks old. It's sunny and warm today so they're in a run on the grass outside, where they can see our older girls and they can all start getting used to each other (Hopefully!)