Snowbell and her strange behavior

Hey, I have a question about some of my ducks! One of my muscovies just had 15 new babies in May and they've gotten big enough where I can let them out in the yard with the grown muscovies now. Their mother adores them and will let them peck and pick around her all the time and she won't bother them, the other ducks are pretty good with the babies too, not pecking them any and accepting them. But, one of my female muscovies, Snowbell, will jump on the babies and attack them!!! The babies actually start the fight, they peck her first over things like food if she grabs a bite they were going after or something, or sometimes they might just peck her for no reason, and she will all of a sudden jump up and jump on their backs and start pecking them! I stop it when ever I see this going on, but what makes me wonder why? is because Snowbell has always been the type to ust be really sweet and calm and she never bothers any body, so I wonder why is she being so mean to these little babies all of a sudden???

Well, I guess that's my question I hope this makes sense I just kinda started writing and I haven't read over anything I've written LOL

Thanks if anyone can give me any advice or know what's up with Snowbell!! ;)

so..does anyone think they might know what has come over Snowbell? Maybe she's just not too fond of the babies?? I don't know I just thought some of you other duck people might have had this same experience? ;)

Most ducks are mean to new guys entering their flock. My duck was recently joined by my two 5 week old runner ducklings and he was mean to them at first but they are getting along now. Just wondering how old are those babies? I think everything will settle down when they get used to each other. I wouldn't separate unless she is hurting them.

Thanks for replying back, the babies were born on May 21. They aren't reall old but they are as big as my 1 y/o female mallard!