Yes, feathers and branches and some more things:
Before you visit a tile, the game knows that it's a heathland tile so it will have approximately 400-500 pine trees and 40-50 young pine trees, 1-5 spruce trees, 1-15 young spruce trees, 1-5 birch trees, 0-2 fallen logs, 5-10 branches, 0-2 boulders. These numbers could be way off, they're just my guesses, but you can get the idea.
Once you visit a tile, the game stores exactly where all these things are. If while you were there, an elk walked through, then the game is also storing all the locations of the elk tracks.
Eventually this takes up a lot of space on your hard drive. [7] will trim it down, keeping only the locations where you've been recently and where you've left significant items -- a shelter, a building, some tools or clothing, some traps, a marker, villages, stuff like that.