If housing is left out, plug the holes, otherwise House Sparrows and starlings will claim it in late winter and be impossible to dislodge come spring. If parasites or wet nests threaten the survival of nestlings, replace the nest material with clean, dry wood shavings. Crushed, dried eggshell or oystershell is a valuable dietary supplement that supplies calcium and grit, and helps prevent calcium deficiencies in nestlings. Offer it all season in an open feeder. Eggshells should be rinsed, dried thoroughly in the sun or a 350 degree oven, then crushed into small pieces.
Landlords can also put nest material out for their birds.
Dried pine needles, dry twigs, or a bale of straw scattered in an open area will be used by the martins. Create a supply of mud for them by soaking an area of ground with a hose. Work with other martin enthusiasts in your community. Martin landlords are a very friendly bunch of people, so don't be shy. Stop and introduce yourself to other landlords, and make some new friends.