Snags (i.e., dead but standing trees) are a great resource for hole-nesting or roosting animals. While snow-shoeing out in the back 40 the other day, I came across these apartment complexes and wondered who lived there.
I would love to get a photo of baby squirrels popping out of one of these holes, so I recently moved the game camera opposite one of these snags.
Snags serve a variety of purposes as they stand and decay simultaneously from both the inside and the outside. Loosened bark harbors spiders, mites, beetles, ants, etc. that are harvested by many small, insectivorous species such as chickadees and nuthatches. The inner layers covering the hard sapwood (newest wood in a tree) are drilled by woodpeckers in search of the wood-boring insect larvae and pupae. These “starter” holes might be enlarged for use by roosting birds and small mammals.
As the harder sapwood decays and softens, the snag attracts the attention of Pileated Woodpeckers, whose long, stout chisel cuts oblong slashes into the wood as they excavate for termites and carpenter ants,
leaving the snag looking something like this.
At some point, the decaying roots give way in a strong wind, and the snag topples over to rest on the forest floor, where other detritivores complete the recycling process. Its hole-nesting or roosting tenants just have to look for another home.