Gorgeous pics. Thanks for sharing. I have bluebird boxes, but other birds always stake their claim first. Once when the bluebirds did nest in one, sparrows threw out their eggs and took over the nest. How does one make sure that only the bluebirds nest in the boxes?

You have to be a mean landlord, when sparrows move in ,you have to evict them. Best to do that after sparrows have laid their eggs. The sparrows will go into Martin house's and kill a Martin. They are not wellcome here.
Norm