Patches, If you had a dozen or more
bluebird houses in your yard you would NEVER get a SINGLE
bluebird.
blue birds are EXTREMELY territorial and antisocial and will NOT nest closer than 100yds/meters from any other
bluebird nest or human dwelling. If you space your nest boxes closer than that NO
bluebirds will use ANY of your nestboxes.
Oh and
bluebirds are very close relatives to the American Robin. The European Robin looks a lot like our
bluebird, too.
Purple Martins, on the other hand will not nest at all unless there are large numbers of nest boxes in a very small area. They are EXTREMELY social and form large colonies of birds. They like their apartment complexes to be on a high pole at least 12ft/4meters above the ground very close to a water source like a lake or pond. And like
bluebirds, they like relatively short grassed treeless fields around their colonies.