pullus vs songbird

pullus

noun
  • A chick; a young bird in the downy stage. 

songbird

noun
  • A bird having a melodious song or call. 

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

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