Is it a nestling or a fledgling?

Nestlings These may have been blown or pushed out of the nest and can be distinguished from fledglings by the fact that they will be only partially feathered and in some cases, gape their mouths in order to receive food from their parents. They will not be moving around adequately enough to avoid predators.

Fledglings These are young birds that have recently acquired flight feathers. They are usually found on the ground and are able to hop and run but not fly. These birds should ALWAYS be left where they are, as their parents will be watching and feeding them. They are expert hiders and fledging is an integral part of their development. If you have already picked up the bird, please put it back where you found it. Don’t worry too much about the parents abandoning the fledgling if you touch it, a birds sense of smell is not sufficient to notice.

What to do if you are worried about a cat attacking a fledgling in your garden