common raven vs northern raven

common raven

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

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

northern raven

noun
  • A common raven, Corvus corax. 

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