Purple Martins prefer 2" round holes, BUT, if you aren't around to control the starlings, your chances of attracting martins are greater with starling proof holes than with the round ones IF starling infested.
To starling proof your house:
1. Make new doors with starling proof holes as shown.
2. Keep the bottom of these holes at the same measurements as the regular round ones, one inch from top of floor.
3. Move the porches up so they are only ˝" down from the bottom of the holes. You may still use the sub-floor pull-out trays.
How to make your own starling proof hole:
Drill three 1-3/16" holes as shown, then cut at the dotted lines.
This is another option for a starling proof hole. You may want to try both types, both are equally effective but some prefer this newer style because it conforms to the Martins body shape and is a bit smaller.
