There are tons in my recently built mature tree-less area.

I had a Purple Martin House for about 10 years until we moved to a different house with a heavily treed lot. Purple Martins need lots of room around their houses, at least 20 feet from trees. Are there house sparrows nesting in the house? PMs will be chased away by them so the Martins will not use a house that already has sparrows in it. They migrate back to South America in June and July. I think they're gone for the year and will be back next Feb/March.
That said, I bet the drought has something to do with it. They eat flying insects like bees, wasps, and dragonflies, so if those insects around around, neither will be the Purple Martins.

Well, since PJ says there seems to be plenty of purple martins around I'll have Bob move the house to a more open area and see if I get any Martins next year. I do keep the sparrow nests cleaned out in the spring and then when all hope is gone that the martins will take up residence I block the holes. I do hope there were enough bugs to feed them this year so there will be plenty of martin progeny to return.

we have lots too roselee, se of SA- we have had 4 sets of babies here on my porch, the sparrows are now in a set of nests, we have had 2 wrens hatch theirs and a set of mockingbirds, We have so so many birds out here, I was hoping the scissortails would as well, but no such luck as of yet. When my husband just cleaned out the shed this past weekend. There was a hummingbird nest,- the eggs and nest had fallen. There is an open area where the birds can fly in and out, and of course our chicken food is in there too, so we have lots of "guests" It is so hard to describe how small the eggs were.! Was very neat though