One of the most important naturally-occurring nest cavity sites is the snag . A snag is a standing dead or dying tree that is suitable as a perch or nest site for cavity-using birds and mammals. Snags are produced naturally by fire, disease, lightning, flooding, and drought. Woodpeckers and other small birds feed on insects that are found on snags, and birds of prey frequently use snags as hunting perches. Songbirds that occupy edge or open habitats use snags as singing perches.
Woodpeckers use resonant undecayed portions of snags as drumming sites for territorial signals.
Also consider the number and variety of insects consumed by other birds. Primary cavity nesters depend on trees with fungal heartrots because such trees have softened heartwood allowing easier excavation. Snags should be within 50 feet of the edge of the cut area. On average, 3-5 snags left per acre is sufficient. Other natural nest sites that may exist on your property may be found in or near wetlands or ponds.