Purple Martins Galore!
There are folks here in central Illinois who are quite successful with Purple Martin houses attracting Purple Martins. But I also have friends who have tried putting up houses and all they attract are European Starlings and House Sparrows. Both species are aggressive and once birds of either species have claimed the house, they will keep Purple Martins from landing on the house. And martins do not share their houses with any other species – the house will either be all martins or no martins.
People who make Purple Martin houses are creative – the houses can be all shapes and sizes. And some are elaborate in their detail. I have always wanted to try erecting a house, but it is a commitment. Where I live, I would have to monitor the house daily in spring and remove starts of House Sparrow nests hoping to discourage them. And at the end of the nesting season, all boxes have to be cleaned out and repairs made. With all my bird feeders, bird baths, and gardening, I just never wanted to take on this commitment. But when I see a successful house, I am full of admiration for the person who erected it and is monitoring it. And I am envious because I do not have one.
My cousin Jean and I always go plant shopping the first Friday in May. We have favorite nurseries and greenhouses and at end of day, we can barely fit into her car as it is so stuffed with plants and all that goes with them. This year we tried all new greenhouses and at Zimmerman Greenhouse outside Vandalia, we hit the jackpot. This is a greenhouse owned and run by an Amish family and it is big and beautiful. The plants were in immaculate condition. Everyone who worked there was very helpful and friendly. And no, they are not paying me for this endorsement nor do they even know I am making it, I just liked the greenhouse that much. The Amish family gave me permission to take these photos.
This greenhouse and farm are both lovely, but what really caught my eye were the Purple Martin houses. The father of the family – an Amish farmer – made all of them. He told me he made the first one years ago and put it up at the driveway close to the greenhouse. And a few Purple Martins moved right in. People shopping at the greenhouse liked it so much, he started getting requests to build more. He did and erected five – all in a row along this driveway. He has now sold many. When we were there the first Friday in May, the houses were full of martins and many more were flying all around. I am not sure there were many vacant holes left in any of the houses. I have never seen so many martins in one place and I was mesmerized! All were chattering so this was a very active scene. 
And none were bothered by being so close to a greenhouse and driveway where people were walking, talking, and working.
If any of you have experience with Purple Martins and their houses, please use the Public Forum to tell us.