Baby pigeon

Hello. This is my first post on here.

A pair of pigeons built a nest in our maple tree, and we've had 2 lovely fledglings. They flew from the nest last Saturday, but this morning one of them is back and is just sitting on the lawn. It's alive, but I don't know if it has a problem flying. What should I do? The mother was here earlier, but she just looked at it and flew away. Is it too young to give it pigeon seed? I'd hate anything to happen to it as we have a lot of birds of prey in the area.

snowy