I photographed this in Plymouth, MA

Ivory gulls normally stay well above Newfoundland, living on Arctic ice where they follow whales and polar bears to feed on the scraps and carcasses they leave behind after making a kill.

Until this year, the last report of a fully mature ivory gull in Massachusetts was in the 1800s. Three immature birds were seen in the 1940s. In 1976, another immature bird had been spotted in Rockport.