harebell vs indigo bunting

harebell

noun
  • A perennial flowering plant, Campanula rotundifolia, native to the Northern Hemisphere, with blue, bell-like flowers. 

indigo bunting

noun
  • A blue bunting of North America, Passerina cyanea. 

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