[The bird seems a little shocked by Leo's forwardness, but at this point he's used to Izuku petting and climbing onto his back, so he's terribly patient with this. He'll even lean his head in and try to pull at one of his locks of hair as he's pet.]

I think it's because normally he's magic...but magic isn't really a thing here, right now. He's called a "Thunderbird", a creature with an affinity for electricity. He's immune to it. He could also speak before, telepathically, which I assume was related to him being magic too.