Martins are not, however, prodigious consumers of mosquitoes as is so often claimed by companies that manufacture martin housing. An intensive 3-year diet study conducted at PMCA headquarters in Edinboro, PA, failed to find a single mosquito among the 350 diet samples collected from parent martins bringing beakfuls of insects to their young. The samples were collected from martins during all hours of the day, all season long, and in numerous habitats, including mosquito-infested ones. Purple Martins and freshwater mosquitoes rarely ever cross paths. The major reason people fail to attract martins is that they place their martin housing incorrectly, or their site is inappropriate martin habitat to begin with.
Martins have very specific aerial space requirements.
Housing should be placed in the center of the most open spot available, about 30-120 feet from human housing. There should be no trees taller than the martin housing within 40 feet, preferably 60 feet. Generally, the farther the housing is placed from trees, the better. In the southern half of their breeding range, martins are less particular about house placement. Southern landlords can sometimes place housing within 15-20 feet of trees and still attract martins.