dark-eyed junco vs junco

dark-eyed junco

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

junco

noun
  • Any bird of the genus Junco, which includes several species of North American sparrow. 

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