Answer: There are lots of insects that prey on fresh new birch leaves. Generally they don't cause any harm to the tree and as your trees mature and produce lots of new leaves, you will barely notice that critters have been chewing holes in them. I suspect the insects are long gone by now but if you find any still munching, collect a few and take them to your cooperative extension office or well staffed nursery to have them identified. Once you know what they are you may be able to find a control for them.
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