Black Witch Moth

I had never seen one before, alive or dead, until I found this. This area seems to have a population of either birds or bats that feed on moths, because we keep finding moth carnage there (http://www.projectnoah.org/spottings/493506007, http://www.projectnoah.org/spottings/504256002, http://www.projectnoah.org/spottings/597696005,
http://www.projectnoah.org/spottings/495306003). From afar, I mistook it for a butterfly because of its size and wing shape. Looking closer, however, I could see that the body was too big to be that of a butterfly.