Okay... that's a magpie. And much as I wouldn't want any creature to be injured or die an 'orrible death, that's still a magpie. They kill baby birds all over the place!
Put it in a box in a quiet room, on something soft like an old towel, put a saucer of water in the box with it and then fold the top over so that it's dark. And then leave it alone until tomorrow. If it lives it lives, but usually it's shock that kills birds found by humans.
I'm sure you knew that already so what exactly is the French for "go teach your grannie to suck eggs"? Or the Gaelic? I'm easy.