Great Black-backed Gull

Along with the more common Herring Gull, the Great Black-backed Gull is one of the quintessential “seagulls” of the New England coast, but they have a long and convoluted history here. Early in the colonial period their colonies were viewed as an easy source of eggs and feathers, and by the late 1800s Great Black-backed Gulls no longer bred in the United States. Following official protection in the early 1900s they began to increase and expand southward, aided by the prevalence of open landfills. Peak populations in New Hampshire probably occurred in the 1970s and 1980s, when birds even nested on the roofs of mill buildings in downtown Manchester. With fewer landfills available, the population is in slow decline, and probably closer to historic levels. The only reliable nesting in the state is now at the Isles of Shoals.

Great Black-backed Gulls are regularly exposed to several more modern threats, including chemical contaminants, oil spills, avian influenza, and entanglement in plastic waste or fishing gear, although there are few data on the effects of these on population trends. And gulls in turn can be a threat to other species in their role as predators. During the heyday of gull populations, they both aggressively appropriated islands used by nesting of other species – particularly terns – and actively fed on their nests and young. An adult Great Black-backed Gull is even capable of swallowing an adult tern whole. Although gull populations are lower now, some level of management is still required to ensure successful reproduction by these more sensitive species.

Gulls are opportunistic foragers and are just as likely to eat berries or beg for French fries as they are to raid a tern colony or harass a merganser for its hard-caught fish. They are also problem solvers, as anyone who has watched one repeatedly drop clams on a parking lot knows. Multiple studies have demonstrated that gulls consider several factors when engaging in this behavior. If there are other gulls nearby they don’t fly as high before dropping their prey, since this increases the chance of a different gull stealing the food. At the same time, larger items typically need to be dropped from higher. The distance from where the prey is obtained to an appropriate solid surface may also factor into whatever calculations are going on in a gull’s head.