Great Black-backed Gull

The Great Black-backed Gull is not only North America’s largest Gull but also the largest Gull found anywhere in the world. They are birds that primarily inhabit the Atlantic Coasts of the continent and have been dubbed as the kings of the Atlantic waterfront due to their powerful builds and their dominating attitudes. They actively bully other birds to steal their food and even hunt adult birds like grebes and puffins on occasion. Being the only Gull of its kind, they are powerful omnivores that have captured the interests of birders for decades.

About Great Black-backed Gulls

These birds have been observed by naturalists since the 18th century, with their feathers even having been considered to be fashionable at one point. An observer in 1921 even noted them for their resemblance to bald eagles. After the eradication of the feather trade in the early 20th century, the populations of these birds greatly increased, and their range expanded to occupy more territories along the eastern coast of North America. These birds are some of the few species that have benefited from industrialization, as they are opportunistic feeders that often find food scraps through the refuses of industries and other garbage dumps. Although these birds are rather hard to miss, there is still tons of information about them that continue to fascinate all those who learn more.

● Great Black-backed Gull Photos, Color Pattern, Song
● Great Black-backed Gull Size, Eating Behavior, Habitat
● Great Black-backed Gull Range and Migration, Nesting

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Great Black-backed Gull Color Pattern

These magnificent gulls do not exhibit sexual dimorphism, with both sexes greatly resembling each other in appearance. Adults are white overall with a black back and wings. Their wings show a broad white trailing edge and white primary tips, with reflective spots at their wingtips producing an even brighter wingtip. They have yellowish bills with red spots at the end of the lower mandibles and chalky or whitish-pink legs that seem to blend in with their bodies. Their irises are a gray or pale yellow that has brown flecks and a red orbital ring lining them. Their non-breeding plumages are similar, with the exception of an indistinct dark spotting on the head and neck.

In contrast, juveniles are heavily mottled with white and pale brown while donning a dark bill and pink legs. Their flight feathers are dark brown and contrast with their paler greater coverts, while their tertiary flight feathers are blackish with broad white edges. Their tail is white with an indistinct black bar that is wider in the center. Juveniles take up to 4 years to fully molt into their adult plumages, but some birds may still show some black on their bills and maintain a brownish cast above in their fourth year.

Description and Identification

You can find these Gulls along much of the East Coast of North America on beaches or fishing piers. They are the largest Gulls in the proximity, with their big heads and bills standing out among the flocks of other seabirds. Adults have very dark backs and nearly black wings, which gives them an appearance similar to bald eagles along with their white heads and yellow beaks. While juveniles are harder to identify, their large, bulky size and shape are nearly the same as adults. Their calls do not sound particularly distinct from other Gulls but tend to be rather loud due to their size.

Great Black-backed Gull Song

The calls of Great Black-backed Gulls are similar to those of Herring Gulls but are much lower-pitch, slower, and hoarser. They do not have songs but have a wide range of calls that can sometimes get quite complex. The first call is the long call, the most elaborate and flexible call in their vocal range. This is a loud call that sounds like trumpeting to some. The first notes are longer and lower before getting subsequently flatter and more lower-pitched. Both members of the pair uses this when one of them returns after absence. Males also use it during breeding season. The frequency of this call increases after the chicks hatch. It is similar to the long-call note that they also make during breeding or when a predator approaches its territory. The rendering of it is “keow”.

The second call is the warning call, rendered as yeow. This pitch of this call descends with subsequent notes, and typically varies in duration between individuals. This is most frequent when there is a visitor and or an intruder disturbing the breeding colony. In the event of a predator, they may also give out an alarm call that sounds like a series of “kek-kek-kek” sounds. If they do not take flight instantly, they let out a charge call while diving towards the predator in order to draw them away. Adults also give out a copulation call and a choking call while breeding.

Immatures are capable of the mew call and the begging call when they initially hatch. Parents also use the mew call during courtship and after breeding. The parents give the mew call to the chicks before feeding them. Adult females also utilize the begging call in response to the mew call given by the males.

Great Black-backed Gull Size

Great Black-backed Gulls are the largest Gulls in the world with a body length of 27.9–31.1 inches. Their long and broad wings have a wingspan of 57.5–63.0 inches. They weigh approximately 45.9–63 ounces. They have stout bodies, thick necks, and heavy, slightly bulbous bills. Their legs are medium-size to long, and their tails are medium-size as well.

Great Black-backed Gull Behavior

These birds typically walk or run on land with a lumbering gait. They may jump or hop onto perches by opening their wings and using a single beat for elevation before pushing off with their legs. Great Black-backed Gulls similarly hop down from perches with their wings partially spread. They are strong fliers and spend a considerable amount of their time gliding and soaring with their outstretched wings. Great Black-backed Gulls attack their prey on land with steep dives and strike at predators with their wings and feet. They are also capable of diving and swimming by using the paddling motion of their legs for propulsion.

They nest on their own or in loose colonies, sometimes with other birds like terns, skimmers, auks, eiders, and other Gulls. Males establish a small breeding territory that can go up to 20 feet in diameter, with pairs vigorously defending it during the breeding seasons. Pairs are monogamous and generally return to the same territories every year. During courtship, males display and call to attract females by leaning forward with their heads bent towards the ground while mewing. They may also fly slowly with defined wingbeats. If interested, females join him. Males may also regurgitate food for females during the courtship period. The pair becomes especially aggressive after the eggs hatch, and actively defend their territories and nests against potential threats.

Great Black-backed Gull Diet

Great Black-backed Gulls are opportunistic feeders and are omnivores. They hunt for mussels, crabs, sea urchins, various fish, and marine invertebrates regularly. They may also eat smaller birds and the eggs of other birds. Their bird prey includes Atlantic Puffins, Common Murres, Herring Gulls, Common Terns, Roseate Terns, Manx Shearwaters, Horned Grebes, and other migrant songbirds. Since they are omnivores, they can often be found scavenging for dead fish, carrion, and trash. They also regularly steal food from other animals like diving ducks, terns, puffins, murres, shorebirds, eagles, and sharks. They may also forage for invertebrates on mudflats following shallow tides. Since animal prey is more abundant during the breeding seasons, they typically forage at garbage dumps in winter more than in the summer.

Great Black-backed Gull Habitat

These Gulls forage over the ocean, along shorelines, and at landfills and fishing docks. They rest at open areas like parking lots, fields, runways, and piers. Breeding grounds tend to be at isolated places that are safe from terrestrial predators, such as small islands, rocky islets, saltmarshes, and barrier beaches. Their nests tend to be relatively high above the ground in open habitats close to water, with some emergent vegetation for protection. Their habitats are almost exclusively centered in and around the Atlantic coast of Canada and the United States, but they may travel inland along major rivers during the winters.

Range and Migration

Although these birds were once just non-breeding visitors to Canada, they breed from New England to as far south as North Carolina along the Atlantic Coast. Individuals that breed in harsher environments migrate southwards during the winters and may sometimes wander away to areas as far as the Caribbean Islands. Birds from Maine, the Guld of St. Lawrence, Newfoundland, and the mid-Atlantic migrate southwards towards the Great Lakes region. Some populations around Nova Scotia and Massachusetts remain in their breeding colonies throughout the year and do not migrate.

Great Black-backed Gull Lifecycle

After copulation, females typically only have 1 brood in the entire breeding season, with the clutch size ranging from 1–5 eggs. Both parents incubate the eggs for around 27–28 days, after which the chicks hatch at a fairly active state with open eyes and thick down. They begin wandering around the nest area within a day but stay close to their parents for another 7–8 weeks until they are capable of flight. Some stay close to their parents even after being capable of flight, but most join other immatures for easier sourcing of food.

Nesting

Nest sites are selected on rocky outcrops, grassy knolls, barrier island dunes, and other sites that are above the reach of the high tides. They tend to be placed next to large objects such as logs, bushes, or rocks because they provide a windbreak and a visual screen from the neighbors. Each pair begins building several nests, but the final site is determined by where the female lays her eggs. The same site is reused for several breeding seasons by the pair, but the nest itself is not reused. Both males and females begin building the nest by digging several scrapes and then making a mound with vegetation, feathers, rope, plastic, and other materials. They create a depression in the center to make room for the eggs and the incubating parent. The resulting site is 8–20 inches wide, with the inner cup being 5–13 inches across and 2–4 inches deep.

Anatomy of a Great Black-backed Gull

Great Black-backed Gulls are the largest Gulls in the world with stout bodies, broad wings, thick necks, and heavy and bulbous bills. They have large heads and relatively long heads. Their heads are white, and their bills are yellow, which gives them a distinctly Bald Eagle-like appearance along with their dark wings.

Final Thoughts

Great Black-backed Gulls are spectacular and magnificent sights along the coasts of the Atlantic Ocean. They are unmistakable for their large sizes, and distinctly dominate other birds in their vicinity. As a 1921 observer penned down his observations about these Gulls, his words echoed with his fascination. “It surely seemed to be a king among the gulls, a merciless tyrant over its fellows, the largest and strongest of its tribe. No weaker gull dared to intrude upon its feudal domain.”

These words continue to ring true over a century later, with spectators still being amazed at their powerful demeanors and brazen attitudes. As their populations are relatively stable, if one travels towards the Atlantic coasts off-season, they might just find these large birds in all their glory.

Ornithology

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