dunnock vs hedge sparrow

dunnock

noun
  • A small European and Asian passerine bird, Prunella modularis; the hedge sparrow or hedge warbler. 

hedge sparrow

noun
  • Former name for the bird Prunella modularis, the dunnock. 

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