These birds have always been desirable in the south because they have a voracious appetite for mosquitoes. In rural areas, it was common until recently to see large groups of dried gourds hanging from posts. People placed these for the benefit of martins, who seem to like this type of structure. (In the north, martin houses seemed more like people apartment buildings.) Anyway, while camping in the Big Cypress National Preserve (by the Everglades), we noticed the Feds have erected metal poles with metal arms and plastic bulbs made to simulate gourd housing. The martins appear to be very comfortable in their government provided housing.