Well okay, this one is not on a wire, but a lot of its relatives spend quite a considerable amount of time every day ( and particularly early in the morning!) sitting on the telegraph wires outside our house chirping and tweeting.
This young fledgling was on my neighbour’s roof at the weekend, so perhaps there’s a nest there too (we have at least one, and probably two judging by the number of birds I see flying up there, in our eaves). It kept coming to the edge chirping, and looking over – perhaps building up the courage to fly. I watched for a while and it would come to the edge, then flutter/hop back up the roof, then down to the edge again. I didn’t see it go, but I presume it must have got off safely as there’s no sign of it now.