If you decide to permanently install you martin houses, be sure you have some way to clean out nest compartments. For example, put the house so you can climb up on a tall ladder and use a wire hook to pull out old nest material. Also, put plugs in entry holes to keep out starlings and sparrows during winter. Although martins feed on flying insects, their ability to control mosquitoes has been overrated. Mosquitoes actually provide a very small part of the martin's food.
Studies indicate martins seek food just after dawn until just after dusk.
Most mosquitoes, however, are active at twilight or night and spend most of the day on the ground or in vegetation near the ground. So, the only time mosquitoes are available for martins is a very short period between sunrise and sunset, and then only if the birds are feeding near the ground. Thus it appears the martin plays a very small part in controlling mosquitoes. Thanks are due to members of the Extension Forestry Department and the Institute of Natural Resources for their comments and suggestions. Original manuscript by R.L. Carlton For additional information on attracting martins and other birds, ask you county Extension agent for Bulletin 727, Attracting Birds to Your Home .