bullfinch vs common bullfinch

bullfinch

noun

  • The Eurasian bullfinch (Pyrrhula pyrrhula). 

  • Any of various other Old World finches in the genus Pyrrhula. 

common bullfinch

noun

  • A small bird, the Eurasian bullfinch (Pyrrhula pyrrhula). 

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