Many sparrows nest in the steel tubes supporting traffic lights. This is convenient for them, I imagine--ready-made, not accessible to predators, sheltered from the rain--though it must get hot in the summer and it would seem to impose some size restrictions on the birds. Certainly sparrows in the park seem larger than street sparrows living only a hundred feet away.Anyway, this sparrow family was at the corner of 81st Steet and Central Park West. Usually one of the adults was away at any given time. You can see one of the young (I think there were two in all) in the tube.