Alden is a very social baby and likes to wave and say "hi" to almost everyone we meet. I would say about 50% of people say hi back, a response rate that he seems to find perfectly acceptable. When he really wants someone to respond, he cocks his head to one side in order to get his face directly under the other person's face and makes intense eye contact. He is not easily ignored when he really has something to convey. Absent that need, he's content to just wave and say hello and, if the other person responds - great! If not, no biggie. He tries the next person.
It turns out, he's the same way with animals. He LOVES animals and waves and says hello to every animal we meet. And recently, on our trip to the zoo, he was waving madly and shouting hit to every animal. Of course, the response rate was down quite a bit. As in, none of the animals responded. But, he was not deterred.
And then we got to the parrot. The parrot that says HELLO. I didn't get the first response on camera but the look on Alden's face was completely priceless. He did a triple take and his eyes bugged out of his head. The parrot talks. It was all he needed to try the trick on every other animal the rest of the day.