Japanese beetles are the primary birch leaf skeletonizing insects in the Twin Cities area and the damage has been especially severe this year.

Birch leaves skeletonized by Japanese beetles:
http://www.lifeandlawns.com/wp-content/uploads/2008/07/japanese-beetle-damage-on-birch.jpg

Learn more here:
http://blog-yard-garden-news.extension.umn.edu/2017/07/dealing-with-japanese-beetles.html

Although it's possible that the birch leaf skeletonizer (Bucculatrix canadensisella) has also been active in your area, we could not find any current information about how to control this pest.  If the problem persists, consider asking a forester or certified arborist to assess the tree's health onsite and recommend a course of action.