While visiting my Dad a couple weeks ago, he and I watched the Purple Martins from his front porch. This martin house and gourds were put up several years ago by my aunt and they're really showing their age. However, the martins don't mind at all- they've used these temporary homes over and over again.
My aunt said the birds begin arriving in February and stay through late June or early July. The martin pairs will usually produce one to two broods during their stay. She has two martin houses and two sets of gourds and most all the cavities are filled with nestlings during May and early June. I was entertained by the adults as they captured insects in mid-air- their aerial acrobatics are quite amazing.
It was a cloudy day and the houses & gourds are pretty high in the air, so my photos aren't clear. Most of the martins are gone now. I'll have to plan on photographing them again next year, on a clearer day of course.