Nesting requirements should be taken into consideration when selecting Purple Martin Housing. These requirements serve as a basic foundation to help increase the attractiveness of your martin houses so that you will be better able to attract purple martins to your backyard. Purple martin nest requirements :
Purple martin housing should be made to lower vertically with easy access to nesting compartments.
Entrance hole size: between 1-3/4" to 2-1/4", with 2-1/8" being the recommended.
Compartment floor dimensions: at minimum 6"x6" but 6"x12" being highly recommended.
Compartment vertical height: between 5" and 7" high.
Housing height above ground: Around 10' to 15' in elevation, though 12'-14' is most common.