The raucous, trumpeting sandhill cranes were once called Canada cranes, hence the Latin name: Grus canadensis. Although establishing nomenclature/taxonomy can be a fluid process, even the best of us get it wrong occasionally. I know I do. Is it Baltimore or Northern oriole?
John James Audubon, the naturalist, believed that sandhill cranes and whooping cranes were the same species. He called them both "Hooping crane," even though other early American naturalists at the time referred to them separately. (Remember they were making it up as they went along. There were no books to consult. Audubon was working on that It wasn't like he could run back home and check his Sibley's.)
Audubon writes, "The young are considerably more numerous than the old white birds; and this circumstance has probably led to the belief among naturalists that the former constitute a distinct species, to which the name of Canada Crane, Grus canadensis, has been given. This, however, I hope, I shall be able to clear up to your satisfaction. In the mean time, I shall continue my remarks..."
"The trachea of this bird confirms my opinion that the Canada Crane and the Whooping Crane are merely the same species in different states of plumage, or in other words, at different ages; and, in truth, the differences are not greater than those exhibited by many other birds, both aquatic and terrestrial."
Yet, Audubon perhaps had some doubt on the topic because he ultimately produced a separate watercolor/etching for each.