I put my blind near their hole and left it overnight. For the next several mornings I was back and in the blind, well before sunrise. The little owls would come stand at the rim of their hole, yawn, preen, stretch, and fluff. With sheer luck, I got one photo just as it was spinning its head. I really enjoy photographing mountain bluebirds in the summertime.
Bluebirds use existing cavities in trees for their nests.
Typically these are in aspen trees, but occasionally one might be in a ponderosa pine with its lovely orange bark. After the eggs hatch, there is lots of activity around a nest. The parents make hundreds of trips to their nest as they bring bugs to feed their hungry brood. Usually they are ridiculously tolerant of a person, e.g. me. I can photograph them from about 20 feet with my 600mm lens, and they come and go without the slightest hesitation.