mourning dove vs turtle dove

mourning dove

noun
  • A grey-coloured dove, Zenaida macroura, that has a mournful call, native to North America 

turtle dove

noun
  • Any of several (species of) birds, called by this traditional name, mainly in the genus Streptopelia, of the family Columbidae (doves and pigeons, which also included the extinct passenger pigeon, dodo, and solitaire). 

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