The House Sparrow, Passer domesticus, is an Old World sparrow unrelated to the numerous species of New World sparrows. The bird has spread around the world to general urban ubiquity; they were introduced to North America — among other places, they were let loose right here in New York City in the 1880s — initially with the hope that they would eat pest insects. The rest, as they say, is history.
This is one of those species that lives in virtual symbiosis with humans; its very name suggests its familiarity with us, and our houses. They can nest almost anywhere there is a cavity; they are not above ousting or crowding out other species from cavities, which makes them a problem; where there are no cavities, they will build their own, weaving great big balls of material in trees (I’ve sometimes run across these in Central Park).
On our NYC streets, the lamp posts that support stop lights have a hollow tube near the top of the pole that supports the wire-like beams triangulating the light. I doubt the designer of this structure realized how readily these would be taken up for House Sparrow nests. In fact, there are usually separate nests at each end of the tubes. This time of year, it’s hard to find one of these tubes that doesn’t have a male sparrow in it or near it, vocally advertising his location and all around dapper looks. Plenty already are active nests. Note the metal beam that goes through this about three inches in. These seems to prevent the much larger European Starling, another cavity nester that will dispossess other species from prime nesting cavities, from using these tubes.
Looks like they found a good place to hang out!