There is, possibly, a turorial here, but I have read that the wings and body are piped separately and dried. Then, "glued" together with royal icing while being supported in the position that you want. HTH
Martha Stewart explains them in her wedding cake book. (maybe check her website) JudyDP is correct, the wings are done in pieces then glued together. HTH
Its the same method as the color flow technique in Wilton Course 2 class. Outline with royal, thin down then flood in. wings are done seperately and when dry positioned into a royal iced body. In the class you would use colour flow icing, but royal does the same thing.