Well, it finally became obvious to me today that I was completely wrong earlier this year when I thought that purple martins had found our martin house!
In the spring, about the time that the martin scouts should have been looking for new homes, we saw some birds that looked like juvenile martins – with light colored breasts.
They hung around the martin house off and on for quite some time – but we never saw any adults. I knew there was a possibilty that they were not martins and were instead tree swallows, but I SO wanted them to be martins that I quickly ignored that possibility!
Well, this morning God made it quite clear that they were NOT martins.
A whole huge flock of tree swallows (ALL had light colored breasts) met this morning on our power line out front — presumably organizing their migration south or something!
Though I’m disappointed we didn’t attract martins again this year, I’m actually quite pleased that we have tree swallows! They’re great insect catchers, and are beautiful to watch in their aerial acrobatics! We will miss the swallows – tree and barn – when they leave for the winter, but we always know they’ll miraculously come back!
Morning Star Meadows Farm 
I read somewhere that sometimes you need to play a recording of purple martins to attract them. Certainly their song must be available on the internet. We had them nesting in a big house in my parents garden when I was a kid – lovely birds. Good luck!
I read about that, too! And then I also read that martins don’t really prefer to dine on mosquitoes as I had hoped they would! They’re more for eating dragonflies – which we have plenty of! We’ll see what happens next year! Between fighting off the sparrows from stealing the martin house and everything else that’s going on here that time of year, not sure I’ll have time for setting up the recording!