Raising chicks with their mother?

[ozark hen]

Congrats!! How exciting for you

 

[Swiss-hens]

We have a new chick - but only 1. Of the 7 eggs, only 1 hatched. We have a lovely little chick, mothered equally by both hens. Some of the other eggs started to crack but nothing then happened. Some eggs also seemed to have almost a double shell. Pieces had broken off but there was a further layer underneath. Is this normal? As a first time breeder I think one new chick is probably enough. Any advice on when it would be okay to put it out in the garden? what things do I need to think about?