dark-eyed junco vs snowbird

dark-eyed junco

noun
  • Junco hyemalis, a passerine bird in the passerine family Passerellidae. 

snowbird

noun
  • A bird, Junco hyemalis, the dark-eyed junco. 

  • A person, usually one who is retired, who travels from a cold climate to a warmer one in the winter; one who overwinters elsewhere. 

  • The snow bunting (Plectrophenax nivalis). 

  • A cocaine user. 

  • A bird seen primarily in the winter time. 

How often have the words dark-eyed junco and snowbird occurred in a corpus of books? (source: Google Ngram Viewer )