Ducklings Keep Attacking Runt

[StuporMan]

Hello, I've been raising a batch of call ducks and one has been noticeably smaller than the others, when they reached a week old he was still the size of a newborn to give you an idea. I ended up having to isolate them just to get them to eat because their siblings would strong arm him away from the food.

The runt next to the smallest duckling from his brood at just over a week old
I decided to reintroduce him to the brooder just to see what would happen and the other ducks flipped him onto his back and latched onto him with their beaks. I've tried many methods (introducing them one at a time, creating a little pen out of mesh so they can see but not touch etc) and every time, no matter the amount of time I let pass, results in the runt getting attacked. I'm not sure why they'd do this, the runt isn't sick and they'd been together long enough to bond. Any advice would be greatly appreciated as we're very likely going to have to keep the runt and one other duck for company inside (he's just too tiny) and at the very least he's bonded to people too so he isn't constantly lonely

 

[sourland]

I think your idea of separating it with one non aggressive duckling is a great idea until it starts growing.

 

[StuporMan]

I think your idea of separating it with one non aggressive duckling is a great idea until it starts growing.

It's started growing, the problem is that none of the other ducklings are non aggressive, they all just seem to immediately try to attack.