Fledging - can anyone identify ?

So, just to be clear: you didn't know what this was and came on here to find out. You also didn't know if the other birds were predators or parents. Then, the other birds are definitely sparrowhawks and this is definitely NOT a blackbird. Where did the expertise suddenly come from?
It's definitely a blackbird, as Linda257 says, although I suspect it might be a male juvenile, with the tail beginning to blacken.