birdcall vs nod

birdcall

verb
  • To imitate the cry of a bird. 

noun
  • Any vocalisation of a bird. 

  • An imitation of this cry. 

  • A device used to imitate this cry, so as to lure and catch birds. 

nod

verb
  • To briefly incline the head downwards as a cursory greeting. 

  • To signify by a nod. 

  • To incline the head up and down, as to indicate agreement. 

  • To allude to something. 

  • To sway, move up and down. 

  • To make a mistake by being temporarily inattentive or tired 

  • To fall asleep while under the influence of opiates. 

  • To gradually fall asleep. 

  • To head; to strike the ball with one's head. 

noun
  • A nomination. 

  • An instance of inclining the head up and down, as to indicate agreement, or as a cursory greeting. 

  • Approval. 

  • A reference or allusion to something. 

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