chroïcocephalus

from The Century Dictionary.

• noun A genus of gulls (the hooded gulls), of the family Laridœ and subfamily Larinœ, including many medium-sized and small species which have, when adult and in the breeding season, the head enveloped in a dark or blackish hood or Capistrum. C. ridībundus is the common laughing-gull of Europe; C. atricillia, C. franklini, and C. philadelphia are abundant North American species.