Mother duck singling out one duckling.

[Chloevr]

My Runner duck has 6 beautiful babies.
She keeps picking on one baby. It’s not hurt or weak. She does not attack it with force but keeps pecking it.

I did catch the little baby and he sees very strong and not hurt.

What could cause this?
Daddy is doing a fantastic job and walks with the last duckling hatched. It’s a little slow still and he stay by its side.

 

[Miss Lydia]

I don't know what would be the cause since it seems to be healthy and strong.[Hard to know what goes on in the mind of a mama duck] About all you can do is keep an eye on how mama is interacting with it and if things do start to get worse take it and maybe another for company and then try later to integrate them back into the whole flock when they are older and larger.
That is sweet dad is helping out.