There is one 50yd very dense hedge that I run beside most days just below Portsdown Hill here in Portsmouth. I ran past it this morning and it was teeming with so many small birds, I think they are sparrows, they make a lot of noise and are incredibly active flying in and out of the bushes and branches. They arrive every year.
My niece lives on a housing estate in Maidstone, Kent and they too have one 100 yd tall and dense hedge (owned by the Council) that runs alongside about 6' from their house and garden fence. Some locals have been trying for a few years to get the hedge cut down because it too, teems with hundreds of sparrows at this time of the year, and some neighbours never stop complaining about them. With the help of other neighbours and the Council, my niece and her family have been able to resist their demands.