The phoenix, of which there is only one in the world, is the size of an eagle. It is gold around the neck, its body is purple, and its tail is blue with some rose-colored feathers.
Pliny the Elder wrote that. Anyway, in milder moments, I sometimes entertain the thought of writing an daft conspiracy potboiler about a search for the mythical Phoenix.
My 30 second pitch: Indiana Jones meets Richard Hannay meets David Attenborough. Towering mountains, dark gorges, excessive CGI, spooky rituals, local cult religions, wars, a few Nazis, at least one evil turncoat English ornithologist-spy, lots of sky and mist, white silk scarves, lightning-strike-close-shaves, motorbikes, aerial dogfights, and a happy ending that manages not only to feature HUGE explosions, avalanches, and disintegrating mountains, but also a poignant take-home message that environmental degradation lessens mankind. And the hero and heroine snog backlit by a sunset over the slopes of the Karakoram, etc, etc. There'd be a twist, too, but I'm still working on that.
The most famous of all real-life English ornithologist–spies (and there are many), Colonel Richard Meinertzhagen, was convinced the mythical Phoenix was based on the Lammergeier. Amazing bird. It lives off bones. It carries them to dizzying heights, drops them on rocks to shatter them, then eats the shards. How cool is that?
This theory of Meinertzhagen's is pretty believable (unlike much of his other work). Carrying Harry Potter and Ginny Weasley would have been much easier if Fawkes had been the right size. And it is such a pity that the talented animatronicians at Harry Potter Central didn't know that Fawkes could resemble a real live phoenix, not an attenuated, livid Bateleur with pheasant feathers stuck in its head.