Generally it should be 4 inches in width and 5 inches in length and 10-12 inches deep. It should have a 1.5 inch entrance hole.
Generally house sparrows and house wrens. Both are cavity nesters and will compete with bluebirds for nesting spots.
Not usually, bluebirds normally nest closer to the ground than martins.
House sparrows and starlings often compete with bluebirds for places to build nests.
Bluebirds are generally colored blue.
That would be for chickadees and titmice. Too small for bluebirds.
Bluebirds do sometimes just go in half way. They may be arranging nesting materials or doing something else. Entrance holes for bluebirds should be 1.5 inches.
Generally 16-21 days.
Yes, bluebirds sing.
No, Bluebirds do not mark their territory by purposely pooping in houses. They typically mark their territory by singing, displaying aggression towards intruders, and maintaining their nest sites. If a Bluebird does happen to poop in a house, it is likely accidental and not intentional marking behavior.
fairy bluebirds are from asia
No. Bluebirds are diurnal (daytime) foragers.
Bluebirds benefit from woodpeckers. Sometimes bluebirds use old woodpecker holes to build nests in.