some vultures sleeping in a tree that hunt you when you start chopping is a decent ideaI mean I love zombies raining down on me as I chop down trees as much as the next guy... I think taking your idea of zombie animals for trees would be great though. Maybe have another zombie bird that nests in trees? Another possibility is to have snakes that fall down from a tree.
Now don't mind me as I clear every tree from around my base.