Bluebird box design advice

As I have a large bluebird trail I have been contacted by a number of birders that are not being successful in attracting bluebirds to their boxes. Most of their box designs were taken off the internet.

As I have a large bluebird trail I have been contacted by a number of birders that are not being successful in attracting bluebirds to their boxes.

Most of their box designs were taken off the internet. The hole sizes must be 1 9/16 inches no more no less for mountain bluebirds. Most internet plans are for eastern bluebirds that take a smaller entrance hole.

I hope this helps.

D. Murray Mackay

Ponoka