Not the only one
This crow with his eight tail feathers is not the only thing that’s misleading about the Naturalis collection. The collection that belonged to Joan Raye, auctioned in 1827, contained, apart from the fake crow, several other fake birds.
Temminck also bought a bird of paradise, Le Nebuleus, and two fake doves. He himself described the doves as Columba auricularis, ‘ear doves’.
Good taxidermists are still capable of misleading us today. One of the tragopans - a bird from the pheasant family - in the collection was created especially for the new set-up. The frozen specimen we originally wanted to use for taxidermy turned out to be severely damaged. So, Naturalis crafted a beautiful new specimen out of various frozen ones. It’s impossible to see that it’s a fabricated animal.
So taxidermists can still mislead us today, even though the goal has changed.