kestrel vs windsucker

kestrel

noun
  • The common kestrel, Falco tinnunculus. 

  • Any of various small falcons of the genus Falco that hover while hunting. 

windsucker

noun
  • A horse with the habit of windsucking. 

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