This is one of my Blue Bird houses, They are made out of 30-50 year old White Oak Fence boards. This house is going on 4 years old and every year I get 3 clutches per summer. This year you can see the hole has gotten bigger from all of the birds going in and out. For about a month the Blue Birds and Sparrows would fight all day long. The Blue Birds moved to another box about 30 yards away. Then the Sparrows moved in. When we first saw them, it was January and the coldest day of the year, right at zero. There were 8-10 of them lined up on our gutter, all males. I did a search because I thought they were migratory. The article I found said some become resident and to put food out for them, and build boxes. It wasn't more than a few days after I put the box up and they moved in. This winter I watched 8 squeeze in the box every evening, to help stay warm.
This is one of my favorite pics, I just took it a couple days ago. You have to look close, there are 3 birds in the pic, Ruby Breasted Grosbeak, Blue Bird, and a red headed Woodpecker. OOPS, I haven't down loaded that one yet.