Martins diet almost exclusively on flying insects, but, occasionally eat crushed eggshells when scattered near the nesting area during nesting season. The eggshells provide the necessary calcium for production of the martin eggs. Purple martincan eat as many as 2000 pesky insects a day, including mosquitos. The birds are very clean and will take their own fledglings' waste away from the nesting area for disposal.
The purple martin is very friendly to humans, and usually sits and watches people work close to them. Martins can be tame enough to light on the shoulders of persons who have handled them at an early age. Usually, more of them will be present where there is plenty of human activity.