wood pigeon vs wood-pigeon

wood pigeon

noun

  • The common wood pigeon, an Old World species of pigeon, Columba palumbus. 

  • A very large (up to 650 grams) species of pigeon native to New Zealand, Hemiphaga novaeseelandiae. 

  • Any of several related species of pigeon in the genus Columba. 

wood-pigeon

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