fence lizard vs swiftlet

fence lizard

noun
  • Any of several species of North American lizards in the genus Sceloporus, especially the eastern fence lizard (Sceloporus undulatus), the western fence lizard (Sceloporus occidentalis), and the southwestern fence lizard (Sceloporus cowlesii) 

swiftlet

noun
  • Any of the various tropical and subtropical birds of the four genera Aerodramus, Hydrochous, Schoutedenapus, and Collocalia in the swift family, many of which can navigate in darkness using echolocation. 

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