Click for the full shot AP caught for posterity. I thought maybe he was reaching down to pick something up (while simultaneously shaking Mayor Iorio's hand, I guess). But the AP caption says he's bowing to her.
I guess I don't mind so much when he's bowing to an American. I'm not happy about it, but bowing to foreign heads of state pegs my OH HE DID NOT meter while this just rises to "what a buffoon"-levels of presidential misbehavior.