will a hen "adopt" a chick?

Actually, if a hen isn't already broody, she may kill the chick.

 

Hen/s that are not broody will not adopt them. As speckledhen pointed out, they will in all probability harm them.
It is possible but extremely difficult to have a broody hen adopt new hatched chicks if the timing is right. However, mother nature is very hard to trick as a general rule.
I have had success doing it and as many failures as well.

 

I just had a bantam cochin frizzle roo and hen take on 4 older chicks. I do not think it happens that much though I was told they made good fosters.

 

I dont think this happens in the real "chicken" world, but I have 2 mixed breed hens that are 4 months old and I had 3 pure buffs and 1 BR and 1 mixed chick and had them in the process of introductions......

Anyway my dogs got out(stupid me) and tore up my buffs and BR! There was one lonley chick left after all that and it had some blood on its head. So.......

The hens all of a sudden adopeted the little one (1.5months old)! They took it literaly under their wing and now they look like a family. The baby was immidiatly accepted, but when the other babies were there the hens were kinda mean and causious.

So.....I guess under some extreme cercumstances things like that can happen.

 

no do not put a chick in with a hen. She will kill it and probably try to canabilize it.