I did not even know such a species existed! I came across a reference to it reading an article about the rain forest and how it's classified into different zones [from the ground to what they call the 'emergent canopy' which are the tops of the few trees that grow above the 'canopy'] so, of course, I immediately put it in my search engine and there they were! Weird looking [but NOT ugly as they say, I actually find them quite striking and beautiful] and with an even weirder story of discovery to the point that we don't really know that much about them... A couple of links for you:
https://en.wikipedia.org/wiki/Bald_parrot
(there is VERY little in this one]
https://neotropical.birds.cornell.edu/S ... spp=194136
[not much more here but a wonderful picture of one]
http://www.arthurgrosset.com/sabirds/baldparrot.html
[INFO MOTHER LODE! and with a link to their vocalizations and a field study on them titled "Description of a New Species of Pionopsitta (Aves: Psittacidae) Endemic to Brazil]