It looks like no. The main problem with chick starters vs duckling is niacin. They need 3x more I believe. Since I don't see niacin listed under nutrition at all, and it only says chicken, I'm guessing no.
You can supplement niacin in their water or Brewers yeast. 100mg per gallon of the human grade kind from the store. I don't know what the medicated ingredients are in chick feed so I'm unsure. It looks like it's just added vitamins.
So I did a bit of looking and it appears Amprolium is what makes medicated chick feed medicated. I don't see it in the ingredient list but I don't know if it would go by another name. I hope someone else will chime in that has experience.
This looks like unmedicated chick feed. It will be okay to feed ducklings and to be on the safe side, because ducklings do need, based on what I have read, three times the niacin, I would add a tablespoon per day of brewer's yeast per three ducklings to their food for niacin and B vitamins. And that was one of the longest sentences I have written in a while.