grey partridge vs partridge

grey partridge

noun
  • A game bird in the pheasant family, Perdix perdix. 

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 grey partridge and partridge occurred in a corpus of books? (source: Google Ngram Viewer )