redstart vs true thrush

redstart

noun
  • A not closely related species of warbler native to the Americas, Setophaga ruticilla 

  • Any of various insectivorous ground-feeding birds, mainly of the genus Phoenicurus. Many of the species have a red tail. 

true thrush

noun
  • Any member of the genus Turdus. 

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