francolin vs partridge

francolin

noun
  • Any of various terrestrial partridges of several genera in family Phasianidae, principally in tribe Gallini. 

partridge

noun
  • Any bird of a number of genera in the family Phasianidae, notably in the genera Perdix and Alectoris. 

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