Given how regularly the collection has been visited by members of this forum over the last decade with
no word of this being the case.....
You are welcome to doubt. It's of no benefit to me to lie. I simply want to provide as much information as I can recall given how many people apparently want to see these birds. What you choose to do with it is up to you.
I saw the bird prior to July of 2019, as that is when I moved out of Chicago, and after August 2014, when I was no longer in university. The specific date of the following interaction is lost to me and I do not know when the bird first arrived or if it is still there. The day I visited would have been a weekday and less crowded; I avoid going to tourist sites on weekends. Below is my best recollection.
I was in the Amazon Rising section of the aquarium - the section forms a sort of U shape. On one branch of the U, there's an electric eel exhibit, I will call this branch the exit. In the middle of the U bend, there's the green anaconda exhibit that the U surrounds, and opposite a large tank full of river fish. The other branch of the U, the entrance, is our focus. If you enter through this branch, there is an exhibit near the beginning, on your right, with a sort of riverbank setup. The exhibit is partially submerged, with a few fish and turtles in the tank portion, and partially terrestrial. The land portion is planted with various trees and flora, and there are some ducks and other birds signed. A branch hangs over the water, fairly close to the viewing glass. I was kneeling down to check out the water tank when I caught a flutter to my left out of the corner of my eye, then a little girl that had been standing nearby exclaimed,
"What an ugly bird!"
I looked up, then stood, my eyebrows rising with my body, "He's not ugly, he's a hoatzin!"
"A Who-what's-in?"
"A hoatzin! I've never seen one in person before."
"Eh. It's got a weird head" The kid's not impressed, and she wanders off.
I take a step toward the glass, and the bird cocks its head at me curiously. "You're not ugly at all, are you?" I ask the bird softly, raising my hand to the glass. The bird preens for a moment. Belatedly, it occurs to me to take a picture. I struggle with my purse, searching for my phone. Just as I frame the perfect shot and hit the button, my feathered friend takes flight. The briefest hint of a tail ends up in frame. The bird lands on the ground farther back in the exhibit and I try again, but his form is obscured by the undergrowth. He wanders into the brush and disappears, as if he were never there at all.
Just then, a new voice startles me.
"Did you get him?" a young woman wearing a keeper's uniform has appeared just behind and to my right. It's clear she's been watching me watching my birdie.
"No," I sighed sadly, "Just missed him."
"You're lucky to see him at all, he doesn't usually come out in the open like that when there're strangers around. Must be your hair." she gestures vaguely toward my head.
"My... Oh!" Her meaning dawns on me as I glance down at my red-orange hair. I chuckle and reply, "Yeah, animals and little kids, they're fascinated by it. Seem to love the bright color."
"He probably took you for another hoatzin"
"Huh. Is it just him then? I saw some nest boxes in the exhibit, you're not breeding them?"
"No, sadly it's just him here, no breeding. All the ones in zoos now are related. The Bronx Zoo had a clutch a while back, and they're all from that line. His old habitat is being redone for a new species, so he needed to be transferred. We're one of the few places that could take a hoatzin, so we got him, and his sibling went to <facility I can't remember and that I'd never heard of before. Not a place you'd immediately associate with rare amazon birds>."
"Wow, I didn't realize they were so rare."
"They're fairly common in the wild, but they're hard to keep in captivity. They need a pretty specialized diet. They're folivores, leaf eaters, so you need to be able to provide the right kind of plants for them. <something about Shedd's research and work in the amazon and plant sourcing>."
"Thanks for all the information, I'm so lucky I got to see him. Just wish I'd gotten a picture now."
"It's better that you didn't. I actually came over to ask you not to post any pictures on social media. We had to stop signing him and take him off exhibit for a while. Drew too many people, not all of them calm or quiet. Cameras flashing and people shoving to see. Stressed out the animals."
"Man... some people suck."
"Right? Anyway enjoy the rest of your visit, have a great day!"
In at least one return trip following this initial sighting, I did see the bird again, farther back in the exhibit perched in a tree. If you do go to look for him, be respectful, and wear something roughly hoatzin crest colored on your head.