Are Your Bluebirds Finicky?

We occasionally see bluebirds flying around our neighborhood and landing for short visits. It is always a delight to see them - what an appropriate name - bluebird.

This past year we put up a bluebird nesting box. We did have a few lookers, sparrows mainly and a few blues, but no takers. One day I saw what I thought was a sure sign of residency, for a blue was in and out of the little house carting nest building materials. But in a couple of days there were no more signs of the new neighbors. This year again I have noticed a few birds flying and lighting on the box, darting in and darting out but not to be seen again. My, my, hard to please. What do they want - granite counters and upgrades?

Well, according to a few articles that I read, these are among the things that bluebirds do prefer:

1. a nesting box that is attached to the top of a pole rather than the side of a tree
2. the pole should be in a clearing
3. the clearing should be away from human habitation
4. attach a "sparrow spook" above the nesting box after the first egg has been laid, but before the second one is laid

I live in a forested area, with few clearings, I am not sure that I can set up surveillance to know when the first egg has been laid, and now I have given up hope of any bluebirds claiming our nesting box. However, I think I will move the box further from the house in case any future tenants want privacy.
Maybe I should put up a sign - Wrens wanted.