capon vs cockbird

capon

noun
  • A cockerel which has been gelded and fattened for the table. 

verb
  • To castrate; to make a capon of. 

cockbird

noun
  • The male of a game bird, especially of a pheasant. 

  • The male of any bird. 

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