American Herring Gull (smithsonianus)

(last update: October 30, 2015)

American Herring Gull adult November

Gulls in Coastal Ecosystems of New England
Gulls link multiple coastal ecosystems in the Gulf of Maine.  As terrestrially-based animals, gulls feed on intertidal and nearshore prey, particularly crabs and sea urchins.  In the spring, Jonah crabs migrate from deeper waters into the shallow subtidal and intertidal zones, where they become vulnerable to predation by gulls.  After foraging in the intertidal zone, gulls return to their nesting territories where they defecate.  Terrestrial plants and other organisms can then benefit greatly from the additional marine-derived nitrogen and phosphorus associated with gull guano.  Thus, gull predation on marine invertebrates impacts three ecosystems:  the terrestrial system in which gulls nest and deposit marine-derived guano; the intertidal community, where gull predation on marine invertebrates affects whole food webs; and the subtidal, by depleting populations of important invertebrate predators.  Therefore, a greater understanding of the effects of gulls on natural communities is vital to understanding the functioning of Gulf of Maine ecosystems, and to their preservation.

Gull Population Trends in the Gulf of Maine
Great Black-backed Gulls and Herring Gulls breed in mixed-species coastal colonies from Maine to New York.  After reaching a peak in population size in the 1970’s and 1980’s, Herring Gull populations have steadily declined over the last 25 years.

Trends in numbers of breeding pairs in the Isles of Shoals, NH/ME.

This decline is usually attributed to improved sanitation and closing of landfills with which Herring Gulls are more strongly associated and to reduced fish offal and discards from ground fisheries closures in the early 1990s.  In contrast, populations of Great Black-backed Gulls have steadily increased during the 20th century.

A Brief Natural History of Gulls
On Appledore Island, ME., gulls establish territories and begin courtship in March.  During this time, former pairs re-establish their pair bonds and new breeders locate and court mates for the first time.  Males aggressively defend territories from other males.

Once territories are established, pairs begin nest construction.  Gulls build nests by digging a scrape on the ground with their feet, then pulling up vegetation and lining the nest cup with it.

When nest construction is nearly complete the pair begins copulation (mating).  After mating, the female typically lays a total of three eggs over the course of a few days.  Both male and female take turns incubating the eggs for approximately one month.  On Appledore Island, most eggs are laid by May; Great Black-backed Gulls begin laying eggs approximately one to two weeks prior to Herring Gulls.  Chicks begin hatching in late May and early June.

Once the chicks start hatching, the level of aggressiveness of the parents increases immensely.  At this point, adults will attack anything that enters the breeding colony.

Gull parents use both chemical (guano) and physical (hitting the intruder with their feet) forms of attack on intruders.  However, when the chicks grow larger and more independent, the level of parental aggression decreases significantly. 

The male and female spend much of their time feeding and defending the chicks. Chicks eat a variety of items including fish, marine invertebrates, mammals (an occasional muskrat or mouse), other birds (gulls and sometimes passerines), and garbage (especially hotdogs, beef, and chicken).  Adults forage away from the colony and return with food that has been stored in their crop.  Adults must then regurgitate the food in order to feed it to their chicks.  Gulls are attentive parents and can be quite tender with their chicks.

Chicks take approximately 8-9 weeks to reach adult size, attain adult feathers and lose their fluffy down.  At this point, chicks are ready to “fledge,” or fly away from the nest.  Fledglings will often follow their parents to foraging sites for a few weeks learning by observing their parents. 

Most Herring Gulls reach reproductive maturity at 4 yrs (although some may attempt to breed in their 3rd year). Great Black-backed Gulls breed at 5 years of age (although some may attempt during their 4th year). Juveniles typically disperse away from the breeding colony during these early years and if they survive, will often return to breed at the same site where they were hatched.  Through banding, we hope to find out how many juveniles return to the island and whether juveniles of one species tend to return more than the other.

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