In reply to ceri:
Bit harsh that, ceri.
I've got a few young birds on the go, including a jackdaw called Derek. He's doing fine, and we're introducing him to the local jackdaws, who now turn up and sit around on the wires when he's out in the back garden. Once his flying gets a bit better, they'll probably take him on.
We do get quite a few healthy fledglings in the surgery (we rear for the local RSPCA centre as well), with a large number of blackbird chicks, which look like young thrushes. They get turned out of the nest a couple of weeks earlier than would be expected, and then spend their time living in the undergrowth and learning to feed, accompanied by a parent. These are probably the young birds most commonly judged to be abandoned.
Derek supposedly fell down the chimney, but as he's hands-down the most annoying bird I've ever reared, I'm pretty sure his parents threw him out of the nest.