A bird pair may have the perfect bond, but there are a LOT of birds out there competing for nesting sites.  I am confident that, no matter how many bird houses and platforms I installed, there would be disagreements as to who gets a given location.

I remember when a Chickadee built a beautiful, soft moss base for her nest.  A Bluebird pair came along and stole it from her -- adding a bit of grass on top.  (The Chickadee started over in another house -- the same house she has used 3 years running.)

In this post, the Bluebirds take on the Downy Woodpecker

Believe it or not, territory disputes begin as early as December. Two woodpecker species (Downy and Northern Flicker) have spent winter nights inside the bird houses here -- a practice called "roosting".  All goes well until someone else decides to move in for nesting purposes.

In this feature, the Bluebirds started checking out the Downy’s roost in December.  By January, the Bluebirds were “playing around” in the house -- and the Downey took up Chamber Maid duty.  

By early February, the Bluebirds took ownership of the house – chasing the Downy away.  The Downy goes back to sleeping in trees.  The Bluebirds have a house.