birdsong vs common raven

birdsong

noun
  • A vocalisation made by a bird for the purposes of courtship. 

  • Vocalisations made by birds, considered collectively. 

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 birdsong and common raven occurred in a corpus of books? (source: Google Ngram Viewer )