Why would you want to keep the bluebird houses mounted in a...

Why would you want to keep the bluebird houses mounted in a place that you now know is unsafe for them? Bluebirds are not ornaments for pictures, they are living things that deserve your best effort if you are going to be a landlord to them. There is no magic spell that will protect those bluebirds--they have to depend on you or they are doomed.