A pair of european starlings is nesting across the street from me in a neighbor’s cable & telephone box. It’s a metal box, about the size of a shoebox, with wires sticking out in every direction. There’s a small hole in the bottom of the box, & the starlings fly in & out all the time, squishing past the wires.
Yesterday I got a look into the sparrow’s nest. It’s very interesting. The birdhouse is filled to the brim with twigs & such, & there’s a tunnel going into it that slants upward. After a few inches of this it drops down into the nest hole, where the eggs are.