After having this housing setup for 6 years, 2 of those in S. FL, we finally had ONE brave pair nest all alone, and very late in the season for them. We live in the Jonesville area and the closest colony I know of is at the Archer Rd. dog park but there could be others. The last few years we have had late season visitors check out the gourds but this year they showed up mid-season and we are thrilled that a pair actually stayed and today 4 fledglings are out flying around with the parents. The parents are 2nd year birds, the male for sure anyway, he is not yet in fully dark purple plumage as he will be next year. The plumage difference is more subtle on the female in 2nd vs. 3rd year birds.
They used the gourd with an enlarged hole but if anyone wants more details just let me know. I'll just say we know now to toss the porches and to enlarge all the other holes for next year. They have been a joy to have around and I can't wait to see if we have more next year!
Here is a link to the conservation organization we bought our housing from, the site is full of greats facts and photos: http://purplemartin.org/
p.s. the photo above is before they nested and it's an adult peeking out from the gourd. I may have missed my chance for a "family portrait".