black-headed gull vs laughing gull

black-headed gull

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

laughing gull

noun
  • A common European gull (Xema ridibundus). 

  • An American gull (Leucophaeus atricilla); in summer the head is nearly black, the back slate color, and the five outer primaries black. 

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