common redpoll vs redpoll

common redpoll

noun
  • A bird of the species Acanthis flammea 

redpoll

noun
  • Any of various finches in the genus Acanthis (syn. Carduelis), which have characteristic red markings on their heads. 

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