Annette, that is a great link, I have it bookmarked from a while ago. We have also had a martin house, home made, store bought, and even grew gourds dried them and used them but no luck. This sight gave me some insight into the possibilities why. We have friends about a mile away that get them, their house is in the middle of the field. Ours is to close to the trees and house. DH had martins on the farm and there were also plenty of sparrows, so I'm not sure that is so ture. Sparrows will try to nest in the martin houses, this is why they need to be shut up once they leave and not reopened till the scouts come back in spring.