My second round of hatching chicks

In my May post I described my process for hatching chicks.  I hatched 5 chicks from 7 eggs using a Brinsea incubator.  I did not mention that one of the chicks had part of its intestine protruding, presumably could not digest food, and died 2 days later.  The 4 remaining chicks grew at a steady pace and are now almost the size of their mothers.  It appears they are all hens.

I began chicken keeping with 8 purchased (1 rooster and 7 hens) and 6 gifted hens.  Of the original 14, I am down to 5 including the rooster who is as vigorous as ever.  Since the surviving hens are tough, well adapted birds and almost all their eggs are fertilized, I decided to do a 2nd round of hatching chicks while I still enjoyed their company.
Same procedures for hatching chicks as in May, with 7 eggs in the incubator.  On the 19th day the first egg hatched and 4 more on the 20th day.  Of the remaining 2 eggs one was not fertilized and the other grew but could not emerge from its shell.  Of the 5 that hatched, one was very weak, chirped continuously and did not survive to the next day.  So I have 4 healthy chicks from the 7 eggs I incubated, the same result as my first go at hatching chicks.
I spent much time watching the hatching chicks and took pics along the way.  I placed the camera on a tripod – here is the setup.

The chick inside the egg chips away at the shell to form an elongating crack.

It can take hours for the hatching chicks.  When the crack is well developed the chick applies considerable effort to split the shell.

And then, with a final heave the shell remnants are scattered and the chick emerges.

And here are the 4 of the hatching chicks the next day.

So I now have 13 chicken (almost back to the original numbers) – 5 of the original crew, 4 hatched in May and 4 hatching chicks in August.