black-headed gull vs sea crow

black-headed gull

noun
  • A small gull, Chroicocephalus ridibundus, which breeds in much of Europe and Asia, and also in coastal eastern Canada. 

sea crow

noun
  • The blackheaded pewit, and other gulls. 

  • The Western jackdaw. 

  • The chough. 

  • The skua. 

  • The cormorant. 

  • The razorbill. 

  • The coot. 

How often have the words black-headed gull and sea crow occurred in a corpus of books? (source: Google Ngram Viewer )