Shoot, I did not even notice this post until just now! I have done some wildlife rehab and I do know that birds will let you know when they are ready to fly away. It's best to keep a bird feeder full of black oilers (sunflower seeds) when the babies are ready to leave the nest for good. Black oiler sunflower seeds have a high nutrition and high fat content, which is good for wild birds and most bird species LOVE them. But make sure you don't have any outdoor cats hanging around your house because baby birds don't have the know-how that the adult birds have and they are extra vulnerable their first few months of life. Did you raise the chicks by yourself? Did they have feathers when you found them? How did you happen to get a nest full of chicks? Did mamma bird die or did the nest fall out a tree?

Don't be sad about babies leaving to start a life of their own in the wild. It's the way God intended it, and it is their way of saying, "I am healthy and I am feeling good...thanks for keeping me alive so I could feel the freedom of the open skies and the fresh air blowing through my wings". It's a blessing when they leave the nest. Don't be sad. And when the remaining babies are ready they will also leave.

I don't know what else to say because I don't know how old they are, if they are flying on their own, or what kind of birds they are.