barn swallow vs chimney swallow

barn swallow

noun
  • Hirundo rustica, the most widespread species of swallow in the world; a distinctive passerine bird with blue upperparts, a long, deeply forked tail and curved, pointed wings, is found in Europe, Asia, Africa and the Americas. 

chimney swallow

noun
  • barn swallow (Hirundo rustica) 

  • chimney swift (Chaetura pelagica) 

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