The 2 photos below are typical examples of unmanaged Paper Birch regeneration. Paper Birch will grow in a clump from stumps of harvested, stressed, or dead trees. The more stems there are in the clump, the greater the tendency of the stems to grow away from each other, resulting in a number of small, crooked, low value trees.
Shown below is a single stem Paper Birch which I manually released 2 years ago by cutting down a half dozen or so stems from the same stump sprout. I also pruned the lower branches. It is growing fast and straight. This will ultimately be a large, straight, high value tree.
Single stem Paper Birch originating from seed tend to be much higher quality than the stump sprout Birch. But they still benefit from early pruning, so as always there is manual work to be done to promote the highest value tree.