Snags provide "hawking" perches for flycatchers and resting perches for swallows. Flycatchers perch on a branch, fly out to snatch insects, and then return to the same branch to watch for other insects. Large natural cavities, formed in snags by decay, often provide homes for a variey of mammals including marten, porcupine, bats, bushy_tailed woodrats, northern flying squirrels, and other species. When left to decay and fall over naturally, large hollow snags may provide den sites for larger animals like mink, lynx, red fox, and wolverine. To help provide homes for this wide variety of animals, leave dead trees standing whenever possible, particularly snags larger than 6 inches in diameter and/or any containing woodpecker holes or other cavities.
Use the proper materials. Wood is the best material for birdhouses. Other materials (like metal or plastic) may not insulate the nest enough, so eggs or young could become chilled in cold weather or overheated in warm, sunny weather. Use rough_cut wood slabs, tree sections, or 3ǚ_inch plywood. Never use creosote_treated wood as creosote may kill the eggs or chicks.