A beloved favorite of home and property owners, purple martins feed enormously on irritating mosquitoes. A group of martins living on your property can transform your backyard into a comfortable, itch-free oasis. However, to attract and keep martins on your property, you must ensure you create comfortable quarters for martins. This includes providing the martin with an ideally sized home entrance hole.
Professionals offer varying opinions on the proper size hole to provide for martin birdhouses. Professionals at Wild-Bird-Watching.com recommend a hole diameter between 1 3/4 inches and 2 1/4 inches, while professionals at AttractWildBirds.com recommend holes sized at exactly 2 1/4 inches.
Professionals at AmishGourds.com recommend a special crescent shape for purple martin houses, whether made from gourds or wooden boxes. Amish Gourds recommends a "D" shaped entrance hole with the flat end along the bottom, measuring 3 inches long with the top of the curve a total distance of 1 1/2 inches from the bottom of the opening.
Specially sized and shaped entrance holes for purple martins prevent enemy and predator birds from entering the martins' home. The crescent shaped holes recommended by Amish Gourds are meant to resist starling birds, a natural enemy of the martin.