carrion crow vs common raven

carrion crow

noun
  • The common European black crow Corvus corone. 

  • The American black vulture Coragyps atratus. 

common raven

noun
  • A large all-black passerine bird in the crow family, Corvus corax. 

  • A dark-colored South Asian swallowtail butterfly, Papilio castor 

How often have the words carrion crow and common raven occurred in a corpus of books? (source: Google Ngram Viewer )