Raising chicken with ducks

[Wlorraine]

I have had duck for several years without hatching any eggs. I understand ducks are not good mothers. So I am trying to raise chickens to find a good brooder hen to not only hatch her eggs but maybe some of the ducks eggs, too. I have 3 older ducks and 4 younger ducks that I added this year along with 2 leghorns (a rooster, and a hen) with 3 bantam. But now that the bantams are laying eggs the younger ducks are harassing the hens while the girls are trying to lay their eggs on their nests. But as soon as she leaves her nest they don't bother her for the rest of the day. I don't understand this behavior can anyone give a clue to whats going on. Only new young ducks are doing this, the older ducks mind they own business. Any thought will help. Thank you for your help.