Wildlife Spotting

I have placed this spotting in "Others"; when I first saw it, I thought it might be a fungus. I watched it over the course of several days. The first couple of days there was a good amount in the hollow, then lesser, then more appeared. However, it stayed within the hollow and did not appear elsewhere on the stump. That led me to wonder if perhaps it might be insect eggs of some kind. When I realized the stump was more dry rot than not, I poked at the top where the chainsaw had cut through; the smooth area from the saw had fallen in. I was curious as to whether the hollow connected to the top so I removed the loose piece that had been the top. A little field mouse came straight up into the air from it's nest in the stump! I did no more investigating hoping I had not scared the poor mouse away from its home.