I hadn't heard of it either.
Bartram's Painted Vulture, a bird that formerly inhabited Florida
(Acrylic painting by Narca)
Noel Snyder investigated the mystery surrounding this vanished bird, and with Joel Fry, has published an on-line paper in the journal Zootaxa which proposes, at long last, the acceptance of this now-extinct species – or subspecies – into the roster of North American avifauna. (An excellent review of this paper was written by Rick Wright for the American Birding Association's blog.)
William Bartram was the first naturalist ever to visit Florida, about the time of the Revolutionary War. He left a detailed description of this spectacular bird, whose existence is not recognized by the American Ornithologists' Union, although several ornithologists have independently acknowledged it. Very similar to the King Vulture of the American tropics from Mexico south, the Painted Vulture was likely either a closely related species or a subspecies of King Vulture.
The bird apparently vanished shortly after Bartram's encounter with it, for it was never seen by Audubon or other early ornithologists who visited Florida.
William Bartram and his father John Bartram left an impressive legacy. John was North America's first botanist, called "the greatest natural botanist in the world" by Linnaeus. John was named the Royal Botanist in America by King George III, and the Bartram homestead is considered to be the birthplace of American botany and the first botanical garden in the US. You can visit their home in Philadelphia, now the Bartram Garden and Museum. (I've not yet visited this National Historic Landmark and garden, but certainly hope to see it soon – perhaps as soon as this summer! The museum would like to have this painting of Bartram's Painted Vulture in its permanent collection, and that strikes me as its perfect home.)
The Bartrams knew Benjamin Franklin and named a tree after their statesman friend––Franklinia alatamatha. The tree is feared to be extinct in the wild but still survives in cultivation, descended from the original plants collected by the Bartrams.
Today the Bartram Trail follows William's footsteps through North and South Carolina and Georgia. In Alabama, the Bartram Canoe Trail meanders along waterways in the Mobile-Tensaw River Delta.
William's travels through a truly wild America and his interest in the Native peoples he met are detailed in a marvelous book. If reading the firsthand accounts of early explorers appeals to you, track down the Travels of William Bartram, edited by Mark Van Doren. What a treasure! I also plan to track down another: Judith Magee's 2007 volume, Art and Science of William Bartram, for the pleasure of seeing more of his marvelous botanical illustrations.