Back in my Redwood days, there was a 22 footer I helped fall in '78, an entire day to put it on the ground. Funny thing, it was holding about five hundred gallons of water and crap, collected over the centuries. I was wrassling a block out of the cut, old Ray leans in, takes a swing with a pulaski, and knocks a 6 inch square hole into the hollow. Ray got knocked off the springboard by a column of fluid that looked like used oil, smelled bad. Ray waited for the water to clear, washed off, went back to hacking at the trunk. There were bird beaks, small bones, teeth, rusty sand, acorns left in the debris.
