I love birdhouses, particularly rustic ones.
I have several, but have yet to see any birds make their nest in one.
Last year, in late winter, I decided to clean out the blue bird house. Much to my chagrin, when I opened the bottom, the old nest and 4 pink baby red squirrels fell to the ground! By this time Mother Squirrel was shrieking at me as I was desperately trying to stuff the babies back into the nest. As soon as I had gotten them back into the nest, Mom came along and one by one took them out to an undisclosed new location. I have since learned my lesson and leave my birdhouses to nature and whoever would like to occupy them.