In Europe the Hahn's is also known as the Red Shouldered Macaw, because they are mostly green in color with patches of red on their shoulder and under their wings. They also have a blue green patch on their crown that starts where their upper mandible (beak for the laymen out there) ends 1/3 of the way back.
The smallest of the Macaws, they are around 13" long--just a little bigger than a cockatiel. Some believe that it should not be classified in Ara genus at all but by themselves in a separate genus altogether, Diopsittaca. Three Ara Nobilis subspecies exist: Hahn's Macaw, Ara Nobilis Nobilis, the Noble Macaw, Ara Nobilis Cumanesis, found south of the Amazon in Brazil and having a horn colored beak, and Ara Nobilis Longipennis, the Long Winged Macaw, pretty much identical to the Hahn's, but larger.
In the wild, they are found around the top of South America from Venezuela around and down to Brazil. Behaviorally, they are cavity nesters that form large, very noisy flocks.
Although these Mini-Macaws are small in size compared to their bigger cousins like the blue and gold or scarlet macaw, they are 100% macaw (no matter what their genus.) As pets, they are just as full of personality as the bigger macaws, but in a smaller package. They need to be socialized and handled often. They are intelligent, social creatures that will thrive when raised and treated as a member of the family--they do best when they can eat, sleep, and even bathe with the rest of their flock/family.