kestrel vs lesser kestrel

kestrel

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

  • The common kestrel, Falco tinnunculus. 

lesser kestrel

noun
  • A small falcon, Falco naumanni. 

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