If you discover a nest full of feathers or speckled eggs, or observe a wren or sparrow nesting in the box, you may want to remove the nest. If you really want to attract bluebirds to your site you can feed them. I tried this with a few containers of meal worms which I was able to keep in their container in the fridge until I was ready to use them. To the thrill of our family and our neighbors, a couple of bluebirds used a house and feeder we set up on the edge of a sheep pasture. Our monitoring was nearly daily as the kids and I kept a close watch on the eggs and then the babies as they hatched, grew and flew.
Some bluebird houses are more effective than others.
Two types generally produce good results. The first is the Peterson box with its angled front door and the second is a PVC plastic design with a wooden removable roof. The more square boxes seemed more likely to suffer from dampness and insect infestations. There is a well-organized and extensive network of bluebird watchers. Consider attending next year's annual conference at the University of Minnesota's Arboretum in Chaska on April 15, 2000.