I’ve found at least 86 species of gall-inducers here in Brooklyn, amongst a rather depauperate and heavily invasive biota. I say “at least” because I’ve come across a few that have not yet been described. Check out the ever-expanding gallformers.org database.
Backyard and Beyond 
I always thought RBGrosbeaks were frugivores. I can imagine a scenario where the grosbeak mistook a gall for fruit and prosperes from the protein. I wonder, though, whether they think sweet and fruity or umami when they see a heavily galled tree.