heroine vs songbird

heroine

noun
  • A female hero. 

  • A female lead character. 

songbird

noun
  • Any bird in the passerine suborder Passeri, which are distinguished by a more sophisticated vocal apparatus 

  • A bird having a melodious song or call. 

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