Yes, it is tough to know what they are thinking but there is a lot of information about birds from people who have studied them. I try to keep the birdhouses cleaned out after the season but the birds don't seem to mind building on last years nest. They just find there way into anyplace that they think is suitable. Once the starlings nested in my vent pipe and that was a big problem. I figured they might like a better house so I put up the birdhouse and they have really liked it. It is fun to hear the little birds asking for food when they are young.