I just placed 100 Tuxedo Coturnix quail eggs in my incubator yesterday. Due around the 11th or 12th.
I will go ahead and add a piece of information that I think is very important for everyone to know...
On day 17 and 18 of my last set of quail, they started hatching in large numbers.... then it was extremely slow for the next 12 - 15 hours....
I noticed several eggs had a very slightly noticeable chip in the egg from where the beak had penetrated the membrane and reached the shell, but that bird was not going to be able to hatch itself for unknown reasons....
I began very carefully peeling these eggs, starting at the beak mark, revealing their beak, and then taking tweezers to break the membrane (careful not grab feathers), and removing the film and egg from the bird, and placing it in the incubator. Very important not to pull / tear the membrane from the bird if it appears to stick. It will eventually dry and fall off the bird. What is going on, is these birds are trying to absorb the last of the yolk into their stomachs. I noticed that I opened one a little too early and it's stomach was kind of pushed outward still, so I did not touch it. I laid it in the incubator with the rest of them that I helped out of the egg. They lay on their sides and don't move much for a few hours, but 12 hours later, all birds were dry, and hopping around like normal.
The next day, I thought I'd go ahead and try to go through the rest of the eggs to see if I could save anymore of them. I found several dead birds, and one that was barely alive. They stayed in their shell too long. This will cause death or deformities, such as curled toes, or the birds will have deformed legs and it's sad to watch them try to learn to walk with them.
Ok so the moral of the story..... don't do this until you know it's at least day 18 & 1/2 and most of your birds have already hatched. 70% of the birds you attempt to help out of the egg would have died had you not, so you're not risking much, and if careful, you will end up with many more birds that would have died a needless death otherwise.
Also, all eggs will show blood in the membrane as you tear it away carefully to release the bird. This is normal. It's not because the bird is bleeding.
But, use this advice carefully and at own discretion. Basically, a last resort after your main hatch to try to save the last few. Don't do it too early, but if you do it too late, they're dead.