Bluebird Parents

Have a Bluebird box next-door and finally caught the pair doing their parenting thing...

That would be encouraging and fascinating.
I gather birds take to these boxes with holes in okay.
Do they need encouraging somehow?

Only instances I know of here are in the wild with our endangered parrots and loss of habitat

The Bluebird as native cavity nesters takes very readily to the box with its hole. Eastern Bluebird populations are in decline so many are making these to encourage population growth. Loss of habitat is also a factor in Bluebird population decline. Thanks for your interest!