A tree at the edge of a field

I spent a winter once in Iowa, just outside of town. My window overlooked a farmer’s field. I noticed that there was a large dead tree along the far edge of the field. It stood alone, and seemed to be totally dead. I kept wondering about the tree, why it was there, and why the farmer hadn’t taken it down. It was, after all, quite dead. In the springtime I chose to get my shoes muddy, and I walked across the field to the dead tree. When I came upon it, I found that it had many holes from insects and birds. I could hear peeping from a nest of birds in a hollow arm of the tree, and I could see several types of insects crawling upon the dead bark.