Could it really hatch this early?
It can be a long time between internal pip and actual hatch. And it can be hard to determine exactly what is going on in there. The chick moving means it is alive, which is good, but I don't always see movement. Other than being glad it is alive at this point don't get too excited by what you see.
That 21 day thing for chicken eggs is just a target. Whether they are bantam of full sized fowl eggs, it is not that unusual for eggs to actually hatch (the chick zips and comes out) two days or even a few hours more early or late. There are a lot of different reasons for that: heredity, humidity, how and how long the egg was stored before incubation began, or just differences between eggs. A big factor can be the average incubating temperature. If it is warm they can be early, cool they can be late. But temperature is not the only factor, I regularly have chicks hatch a full two days early under a broody hen, not just in my incubator.
In my first incubator hatch I had a couple of chicks already in external pip when I put them in lockdown after 18 days of incubation. They were OK by the way, just early. After that hatch I calibrated my incubator and it was a little warm so I reset it. Most of mine still hatch early, whether incubator or a broody hen. I think heredity has a lot to do with that. Some people consistently have chicks that hatch late, the latest under a broody hen I've heard of from someone I trust to count the days right was 25 days.
Can eggs really hatch that early? Even if that egg is in internal pip (which it might not be) I would not consider it to be all that early, but yes they can.
