On Huck's hypothesis, that the bird is an imperial eagle, a good site with pictures is
http://books.google.com/books?id=fSvlaZ ... at&f=false. See the pictures on p. 286. He was associated particularly with the bicephalous eagle, or a pair of eagles. But the artist might not have known that. An eagle appears in Plutarch's "Life of Alexander" before a battle as an omen of victory (
http://www.e-classics.com/ALEXANDER.htm). Alexander minted coins with eagles on them (
http://rg.ancients.info/alexander/bronzes.html). And the eagle was his mythical father, Zeus.
Some other possibilities for the bird. One, a phoenix. It was often shown without being in fire; it built a nest first, then burnt up at the proper time. Alexander flared brightly and then went out, to be reborn in legend. If Pico della Mirandola could be called "the phoenix of the age," why not Alexander?
It looks to me more like a waterfowl than a raptor. From that perspective, it might be something in one of the Alexandrian romances that were popular a that time. I can't find any on-line except Gower's, which has no bird.
One episode, in Arabic-based versions, has him searching for the water of life, the drinking of which will make him immortal. In one story, Arabic, bird-men bar his way. In another version, which shows up in Azerbadjan folk tales, he's about to take a drink, and a bird comes and knocks it out of his hand (
http://www.visions.az/literature,219/). A voice tells him that immortality is extremely boring after a while, and he is better off doing good deeds. So Alexander might have the bird's image on his helmet to remind him not to try to prolong his life at the expense of good deeds.That would be especially appropriate in a conversation with Diogenes, who disdained the world altogether, and also poignant considering Alexander's early death.
In Plutarch, stories about birds abound. These would have been well known in Ferrara at that time, as Plutarch's
Lives had by then been translated into Latin. A flock of birds eating at the site of Alexandria auger a great city. according to his soothsayers. These would probably be waterfowls--but it was a whole flock. Also, Ravens or crows--again a flock, and not even waterfowl--lead his party across the desert to the oasis he is looking for, where the priests tell him he is the son of god and destined to conquer the world (
http://books.google.com/books?id=hG7RAA ... ch&f=false). But the bird on the card doesn't look much like a raven.
Alexander was also famous for introducing parakeets into Europe, birds that talked but had no idea what they were saying. An appropriate image for Alexander's advisers, as seen by Diogenes, but the bird does not look like a parakeet.
Also, Alexander was known as a bird-lover and protector. Any bird might do.
I love details like that, Marcos. Thanks for bringing it out. My hunch is that it is something special to Alexander, known in the literature about him available in Ferrara in the late 1400s. My suggestions are inadequate as they stand.