December 2017

Vol. 45, No. 6

Front Cover: December 2017

Herring Gull by John Sill

Herring Gull by John Sill © Massachusetts Audubon Society. Courtesy of the Museum of American Bird Art.

John Sill is a freelance wildlife artist living in the mountains of North Carolina. He was the illustrator for the Bird Identification Calendar for Mass Audubon for many years. His work has appeared in Birds In Art at the Leigh-Yawkey Woodson Art Museum, Wausau, Wisconsin, and in Art of the Animal Kingdom at the Bennington Center for the Arts in Vermont. He continues to illustrate the "About" and "About Habitats" series of natural history books for children written by his wife Cathryn.

Herring Gull

Gregarious and conspicuous, the Herring Gull (Larus argentatus) is our most common and widespread North American gull species. It is a large white-headed gull, which in adult breeding plumage is also white below with a gray mantle and wings, and wingtips that are black with white spots. The legs are pink and the bill is yellow with a red spot near its tip. In winter, the head and neck are finely streaked with brown. Young Herring Gulls usually do not achieve adult plumage until their fourth year. Juvenile and immature plumages are highly variable, change with age, and differ geographically. Thus they can be confused with juveniles and immatures of more than a half dozen other gull species. In general, sub-adult birds are mottled brown with bills that are dark or pinkish with dark ends. To add to the confusion, Herring Gulls frequently hybridize with other gull species. Good luck with identifying molt classes and separating juveniles and immatures from sub-adults of other gull species! Six subspecies of Herring Gull are recognized worldwide by some authorities, but only L. a. smithsonianus breeds in North America.

Herring Gulls have a circumpolar breeding distribution. In North America, they breed from Alaska to Newfoundland in a broad swath across Canada, including parts of Baffin Island. In the United States, their breeding colonies are found in the Great Lakes region and from New England south to North Carolina. Most Herring Gulls are partial migrants or nomadic except for birds nesting in eastern Alaska and along the East Coast from Massachusetts to North Carolina, where they are year-round residents. The migrants winter along coastal areas in the west from northern Canada south to central Mexico, and in the east from North Carolina south along the Gulf coast to Belize, the Caribbean Islands, and parts of Central America to Panama. They are also found inland throughout the southern states west to Oklahoma and in limited numbers north to the Great Lakes.

In Massachusetts, Herring Gulls are locally abundant breeders, particularly along the coast and on islands, and are abundant migrants and wintering birds, primarily along the coast. Herring Gulls did not nest in Massachusetts until the twentieth century. Eggers and plume hunters seriously reduced their numbers until the 1930s when protection and ready access to large food resources provided by garbage dumps and other human refuse caused spectacular population increases. Herring Gull populations have since stabilized and are actually now declining, partly due to the closure and capping of dumps and the cleaning up of harbors in Massachusetts.

Herring Gulls are monogamous and mate for life. They are territorial and defend the nest site aggressively, particularly when the young chicks are present. They have several calls and displays that are given in a variety of circumstances. The long or trumpeting call functions in individual recognition and is given by both sexes when a mate returns to the nest. The mew call, a single drawn out note, given while in a forward bent posture with neck extended, is performed during courtship, nest relief, and in aggressive situations. The choking call is given by the pair as they crouch, breasts forward, tails up during early courtship, nest relief, and territorial disputes. Another display includes an upright posture, usually by the male, with neck stretched upwards and head pointed down, and sometimes the wings slightly lifted, which is common during territorial defense. This may lead to a charge, running at an intruder with wings flapping. In territorial disputes the male may pull grass, which is considered a threat display. Head-tossing by females and young may serve to elicit feeding by the male. Males may mate-guard females early in the nesting cycle. In winter, Herring Gulls defend feeding areas, for example, on beaches, and some gulls defend feeding areas year-round.

Herring Gulls nest in mixed-species colonies that sometimes number in the thousands of pairs, usually with other gull species. They prefer islands or other areas that provide protection from mammalian predators. The pair selects the nest site, usually protected from the wind near a shrub, rock, or other large object, and usually in an area with vegetation. The nest is a scrape lined with feathers and vegetation. They may make more than one nest but only use one. The typical clutch is three smooth, olive to greenish eggs, spotted or splotched with dark colors. Both sexes develop three brood patches and share incubation duties for about one month until hatching. The chicks are semi-precocial: their eyes are open, they are covered with down, and are capable of leaving the nest hours after hatching. Both parents brood the chicks for the first week or so and during inclement weather thereafter. Herring Gulls will mob mammalian and avian predators. The young fledge after six or seven weeks. The parents feed the chicks by regurgitation on their territory for three to four months, as well as for several months after leaving the territory.

Herring Gulls feed on a wide variety of marine organisms including invertebrates, fish, and the eggs and young—and occasionally adults—of other seabirds. They also are scavengers, feeding on carrion and frequently pillaging human garbage dumps. Accomplished predators and scavengers, they will follow an outgoing tide to catch worms, dive into shallow water for invertebrates, and follow fishing boats for scraps and bycatch. Herring Gulls dropping bivalves or gastropods from heights onto hard surfaces to break them is a common sight. They are the ultimate foraging generalists, although individuals may specialize.

Herring Gull predatory behavior impacts other seabird species at nesting colonies, which has prompted human intervention through culling and egg destruction. They are preyed upon by eagles, falcons, and owls. Breeding colonies are preyed upon by foxes, domestic dogs, raccoons, and herons. Their generalist foraging behavior also exposes them to pesticides and other harmful pollutants. Herring Gulls have not fared well in areas with expanding Great Black-backed Gull populations, and human development often restricts breeding habitat. However, their circumpolar breeding distribution and flexible foraging behavior bode well for the future of Herrings Gulls.

William E. Davis, Jr.

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