Airy and with a view.
I’ve posted pictures of these traffic light support poles before. Practically every single one has a House Sparrow nest at both ends. And the birds are staking their claims over them now, actively! See also yesterday’s post.
This was on the long 5th Avenue border of Green-Wood. Along this same stretch, I’ve come across an all-natural, wild House Sparrow nests, a football-shaped conglomerations of woven material. Here’s another.
A couple times in different Brooklyn neighborhoods, I’ve seen crows check out these traffic light tubes, one hole at a time, presumably looking for sparrow eggs or chicks.
Backyard and Beyond 
In the British Isles House Sparrow is a rural bird and in decline. Here there are four nest sites at every traffic light country wide. The birds are in no shortage here. Nest availability has to be part of the reason. The “natural” nest is similar to Weaver Finch nests on a small scale. You could draw a comparison to the Monk Parakeet nests at Green-Wood Cemetery, too.
I was surprised by their absence when I was in London and Dartmoor in 2013. Only noticed them once, around a farmhouse.