great grey owl vs night owl

great grey owl

noun
  • Strix nebulosa, a very large owl. 

night owl

noun
  • An owl (order Strigiformes) that is nocturnal. 

  • A musical instrument which imitates an owl's hoot, consisting of a receptacle partly filled with water and a mouthpiece that is blown into. 

  • One who goes to bed late, or stays up late at night or in the early hours of the morning. 

How often have the words great grey owl and night owl occurred in a corpus of books? (source: Google Ngram Viewer )