In London last week I cycled round a corner and a Magpie was pecking the absolute shit out of some small brown fledgling right in the middle of the road - fledgling was squeaking away in distress :( Magpie flapped off when I arrived on the scene and the fledgling ran into a bush.
We think it was Magpies. RIP Blackbird chicks :(
(For avoidance of doubt, that is just the old nest, no chicks could be found)