The Bird sNest Box by All Lovely Stuff is made by mounting the pot sideways and closing it with a disc of Douglas fir plywood, which has a hole for the bird to get in and a wing nut underneath for a perch.
Who says a bird house needs to be an actual house? How cute is this tea pot bird house? Just place the pot in a standing up position beside a wall. You can find all sorts of teapots at The ReUstore. Be creative!