My hen is pecking at her new baby!

by Shawna
(USA)

Yesterday our baby zebra finches finally left the nest (6 total). Once the were out of the nest...I started to observe them closely and noticed that one of them is alot smaller than the rest. It appears to have a kind of "fluff" to it still as if it could be younger than the rest. Today, the mother and father both have started pecking at it. They try to push it from perches as well and I don't know what to do!! Since they are not old enough to eat on their own yet, I haven't removed it from the cage because I'm not sure how it will be fed and live. I've seen my male and female do this to each other during nest builing but I can't figure out why they would do this to one of the babies. Please help!!

Thanks!
Shawna