What is the first thing you think of doing with a tree that has died on your property? My guess is that you plan to have it taken down and hauled off. If you have enough room and if and when that dead tree falls it would not likely cause any damage, I want to encourage you to leave it in place instead.
Many birds and mammals rely on tree cavities for nests, shelter, preferred perches and storage. Some live trees do have cavities but it is the dead trees or snags that provide the majority of the cavity space needed by wildlife. Knowing this, I leave my snags when I can for wildlife habitat. I did have a large sycamore that succumbed to drought removed many years ago because it had the potential to take out my tack room when it fell. You do have to carefully evaluate the potential for damage from a snag when it falls before deciding to leave it in place.
And snags, because they are dead and decaying trees, will fall. We had a storm with hurricane force gusts earlier this month and I lost portions of two snags that I had left in place. While we were cleaning up a portion of one of the snags that had fallen, we discovered another critter that benefits from the cavities in snags, honey bees. Another section of the snag we had been clearing had come down nearby and come to rest still standing fairly vertically. It had a very large number of bees that seemed to be forming a living scab over what most likely used to be a more covered cavity. They were a docile bunch and bees are beneficial so I did not want to have them removed from my property if they were likely to be ok after the partial destruction of their home.
I had a chance a couple of days later to speak with a honey producer that was very knowledgeable about how bees cared for themselves in the wild. The advice I received based on my input to the honey producer was to watch them to make sure the repairs were progressing and that they should have enough time to get their house in order before winter hit. They do seem to be making great progress building new honeycomb. Having a chance to watch them up close, I have seen many bees returning with full pollen sacs and even saw one bee doing its dance to communicate with the others in the hive.
I'm glad I have been able to provide a place for a wild nest of honey bees (especially since they are a docile bunch). I never noticed they were in that old snag until the storm brought their home down to eye level.