The Apus illustration wasn’t based on a paradise bird itself, but in its first (rightfully) rejected run it was based on the Strelitzia reginae, also commonly referred to as bird of paradise or crane lily. The Pegasus should be relatively self-explanatory.
Slawik, E., & Reichert, U. (1998). Atlas der Sternbilder: Ein astronomischer Wegweiser in Photographien [224 S]. Spektrum Akad. Verl. Heidelberg, S. 100, 152.