The unmistakable hole-punch round chunks that are missing in these redbud leaves are evidence that leaf-cutter bees are nesting nearby. Leafcutter bees line their nests with these carefully cut-out pieces, creating a multiple celled nest - one for each larva & its pollen food source.
An important pollinator, leafcutter bees are dark bees about the size of a honey bee -- I'll have to keep an eye out for them.
There are so many different kinds of bees to learn about! Here in North America, there are some 4000 species of native bees.
Bugguide.net has a wonderful site to poke around, with all sorts of useful information. Here's their bee page.