This bowl was handmade out of chestnut and has some spalting and natural inclusions.
These holes are formed by cavities in the bark of the tree that are carefully preserved when making the bowl.
I made a video about the turning of this piece. You'll see a Walnut finial added in the video, but that sadly cracked, so I turned a new one.
[embedyt] https://www.youtube.com/watch?v=t1OR3d0s88c[/embedyt]