Airborne opportunists

Perhaps no animal sound evokes the sea better than the plaintive cry of the gull. Yet gulls are the Rodney Dangerfields of seabirds. Whereas albatross are renowned for their phenomenal flying ability, terns for their grace, and puffins for their quirky charm, gulls get little respect. Some mariners even consider these underappreciated birds “rats of the ocean,” owing to their widespread abundance, ravenous appetites, and sometimes unpleasant habits, such as swathing boat decks in guano. But gulls rank among the most ecologically successful of ocean creatures, reason enough for anyone who spends time on the sea to learn something about them. With practice, it becomes possible to distinguish species that otherwise might seem identical. And, like any creature that manages to achieve such prevalence, gulls possess a host of remarkable behaviors, physiological adaptations, and ecological patterns, having rebounded from regional extinction just 100 years ago.

Worldwide, there are some 44 different species of gulls, including 29 in the northern hemisphere. At least 22 species occur in North America or surrounding waters. The name “gull” itself may be derived from the ancient Breton word goelaff, meaning “to weep,” possibly in reference to wailing cry of these birds. To call these creatures “seagulls” is misleading, however, as most species are associated primarily with the coast, never venturing far offshore; indeed, many gulls even reside thousands of miles inland. Among North American gulls, only the black-legged kittiwake and red-legged kittiwake regularly venture far offshore.

Although today’s mariners may curse gulls for fouling decks and docks or dismiss them as garbage-rummaging vagrants, a traditional European legend holds that the birds are reincarnations of drowned fishermen or sailors and, as such, are worthy of respect. Across the Atlantic, Longfellow told of gulls nobly rescuing Hiawatha from inside a sturgeon by ripping open the giant fish’s stomach. And in 1848, as food crops of the Mormons fell under attack by swarms of hungry grasshoppers, flocks of gulls appeared, as if by miracle, to devour the disastrous insects. In grateful memory of God’s mercy, the Mormons later raised a monument to the gulls.Flying garbage disposals

Such a voracious and indiscriminate appetite has served gulls well and is the chief reason for their continued ability to grow in population amid an increasingly human-dominated world. Remarkably omnivorous, gulls eat everything from fish, clams, starfish, and oysters to mice, voles, and insects to bread, fries, and discarded hamburgers. As one observer put it, gulls consume “practically anything they can swallow.” And they are quite resourceful in obtaining meals. Often, for example, a herring gull will pick up a mussel or clam with its bill, fly high above a rocky outcrop, and drop the prey. If the shell cracks, the gull begins feeding on the exposed meat. If not, the bird may repeat the process until the shellfish successfully shatters. Perhaps the most skilled of all gulls at catching live fish is the kittiwake, the only gull able to swim underwater, using its wings as fins. The kittiwake either alights on the surface of the water and pokes its head underwater to catch prey or dives from the air to chase capelins or lance fish as deep as six feet.

Though gulls can drink fresh water and sometimes seem to prefer it, they are quite capable of drinking salt water without any ill effectsan important adaptation for a creature that spends much of its life bobbing on or soaring above briny water. Previously it was believed that gulls used their kidneys to remove salt from their drinking water, but later research showed that those organs weren’t up to the job. Eventually, scientists discovered that like other seabirds gulls possess specialized glands to handle this important function. Embedded in the head above the eyes, the glands concentrate salt from the body into a fluid excreted through holes in the bird’s bill. The characteristic quick head-shake of gulls and other seabirds is an effort to shake the salty residue from the bill.

Gulls display a number of adaptations that help them attain rather old ages. In captivity, gulls have been documented living well into their 40s. In the wild, they may not survive quite so long, although one individual was documented to have lived at least 28 years. One helpful adaptation enables gulls to stand in cold water or on ice without freezing their feet. Lacking any feathers on their legs and feet to act as insulation, gulls instead are outfitted with small valves that pump blood quickly into the chilled body parts. The blood pressure generates heat to guard against frostbite. Gulls are also aided by their uncanny navigational abilities and the capacity to fly at speeds of 40 to 50 miles per hour during migrations. Even when relocated 300 miles from their nest sites, gulls can steer themselves back home with tremendous precision, and from year to year they reportedly return to within feet of their annual nesting sites. The exact navigational cues on which they rely are unknown, but scientists speculate that the birds use geographical features as guideposts, much as sailors do when piloting along a coast. Gulls might also rely on the sun as a beacon, because their direction-finding capability is measurably greater on sunny rather than cloudy days. Often gulls soar to great heights on thermal currents formed when the ocean water is warmer than the air. These updrafts lift the birds skyward, requiring little effort on the gulls’ part. By gliding from one updraft to another, a gull can travel huge distances without so much as flapping a wing. Many gulls migrate from summertime habitats in the north to winter breeding grounds farther south, relying on these flying and navigational skills.

The life cycle of a gull begins with the laying of an egg, often on a rocky cliff or island that offers protection from predators such as foxes, hawks, and eagles. Adult gulls guard their eggs, typically laid in batches of two or three, vigilantly during the month-long incubation period. Finally the egg hatches, and a downy little chick emerges. Flightless for four to six weeks, the brown chick depends on its parents for food, pecking at their bills each time they return from foraging. Then the young gull learns to take wing and joins the adults for life away from the nest. After two to four years, the gull matures and repeats the cycle anew by finding a mate with which it may pair for life. Before a gull adopts its adult plumage, however, it molts several times, changing radically in appearance along the way. Sub-adult color patterns are extremely variable, but gulls typically are some shade of brown as youngsters.

Variable markings often make it difficult to identify the species of a particular gull while it is young. Yet adult gulls generally do show noticeable differences in body size and colors, depending on species. The most commonly seen gull in North America, ranging up and down both coasts and inland, is the herring gull. Some 25 inches long, a herring gull in breeding colors features gray topsides, white head and underbody, pink legs and feet, and a yellow bill with a red splotch. The herring gull is a remarkably adaptable bird that inhabits seemingly every conceivable aquatic habitat, from rocky shores and estuaries to lakes, rivers, and beaches. It also commonly resides in decidedly non-aquatic habitats such as garbage dumps, where it scavenges meals. Otherwise, the herring gull’s diet consists of virtually any scrap of marine animal, along with plant matter such as berries. (In Maine, herring gulls have been reported eating blueberries.) The herring gull breeds from Alaska and Greenland southward to the Carolinas, as well as Eurasia, and its range continues to expand, a sign of its ability to find an ecological niche by exploiting the largesse of mankind. The herring gull’s nest shelters two to four mottled olive- or brown-colored eggs in a clump of seaweed or dead vegetation, either on a cliff or on the ground.Other species

Often joining the herring gull in its breeding grounds is the great black-backed gull, a notorious predator. North America’s largest gull, the great black-backed gull sometimes measures nearly three feet from head to tail and can be readily identified by its large size, white head, black mantle, and pink legs. Distributed along most of the U.S. East Coast, as well as in Europe, the great black-backed gull has been expanding its range over the last century, much like the herring gull. To see this giant gull in 1833, Audubon traveled all the way to Labrador, but the species is believed to have begun breeding as far south as Maine in 1928 before spreading to Massachusetts by 1931 and New York by 1942. Although warier of humans than the herring gull, the great black-backed gull preys upon small ducks and seabirds, including their eggs and young, as well as fish and shellfish. It typically lays three olive-colored, spotted eggs in a grass-lined nest on the ground.

Dozens of other gull species, each with their own markings, also cruise the airways of North America. Somewhat similar in appearance to the herring gull is the ring-billed gull, distinguished by its yellow legs and the signature dark band around its bill. Found on both coasts, ring-billed gulls sometimes form huge nesting colonies. On one island in Lake Ontario, more than 85,000 pairs reportedly nest together, unlike the herring gull, which often nests in groups of less than a hundred pairs.

At least six species of gulls found in North America have black heads for at least part of their life cycle. Among the most widely distributed of these are Bonaparte’s gull and the laughing gull. A small, delicate-looking bird, Bonaparte’s gull features red legs and a black bill, and its head also turns black during the bird’s breeding phase. This species ranges along both the East and West coasts, into Canada and Alaska. The laughing gull, in contrast, is common along the East and Gulf coasts and the Caribbean, although its numbers have dropped in some places as herring gulls increased. During summer, adult laughing gulls have black hoods, but this feature is not present in winter or before the bird matures. Laughing gulls are known for their agility in flight, as they can nimbly catch morsels of food thrown into the air from the deck of a boat. In some places, laughing gull nests intermingle with those of terns.

Whereas the great black-backed gull often eats tern chicks outright, on Petit Manan Island in the Gulf of Maine the laughing gull has been observed practicing kleptoparasitism, the theft of another animal’s food. Observers found that whenever a tern flew homeward from a foraging run at sea, bearing a herring or other small fish with which to feed its young, it risked being attacked by one or several laughing gulls. Before long, the larger birds would rip the fish from the tern’s mouth or force it to be dropped. Apparently the laughing gulls relied on these easy pickings to feed their own chicks because the aerial assaults only began in June, just after the gull chicks had hatched. Intriguingly, the laughing gulls didn’t share their booty with their partners in crime, unlike wild dogs and other creatures that maraud in packs. Instead, only one gull would make off with the prize. Evidently the gulls realized a higher success rate when attacking together than singly. Otherwise they would have carried out the raids on their own. Some biologists believe that loss of food to the kleptoparasitic gulls may have been so prevalent that it affected the terns’ population size.Exotic gulls

Perhaps the world’s most beautiful gull, if that’s not an oxymoron, is the swallow-tailed gull, found in the Galapagos and along the coast from Panama to Peru. With its black head setting off patches of white, along with crimson-ringed eyes and red feet, this bird cuts quite a sharp figure. But this species is most notable for its feeding behavior. It is the only gull that feeds primarily at night, a fact that wasn’t discovered until Jack Hailman, an ornithologist from Duke University, snuggled up to the birds’ cliff nesting sites in his sleeping bag during the fall of 1962. Hailman witnessed the seemingly fearless birds, which had never previously been observed feeding, launching themselves across the dark, nighttime sea. There they collect squid, which only surface at night, before returning home to feed their chicks. Biologists speculate that this behavior might have evolved either to enable the gulls to avoid competition with other seabirds for daytime food sources or as a way to avoid the notorious frigatebirds that maraud the islands during daylight hours. Either way, the swallow-tailed gull, previously mistaken as a form of tern, now boasts the largest, most light-sensitive eyes of all gulls, and its chicks sprout bright white feathers on their heads so as to make themselves readily visible to their parents after dark. The adults, in turn, bear a white blaze on their otherwise black bill, a mark that stimulates the young to peck hungrily for food. Today, swallow-tailed gulls can be viewed feeding in the nighttime wakes of boats passing among the Galapagos Islands.

Another bird of the Galapagos archipelago ranks among the rarest of gulls. The so-called lava gull numbers only some 400 breeding pairs, all confined to the Galapagos. The dapper appearance of this gullits body of sooty gray, with a darker head and white rings encircling its eyesbelies its habits as a scavenger. Typically, the lava gull feasts along the shoreline, where its coloration offers camouflage from felonious frigatebirds that might attempt to make off with its food. This stands in sharp contrast to other species, such as the herring gull, which flies a figure-eight pattern and squawks a characteristic call, audible up to three miles away, to alert others of its kind to food. Even so, the lava gull is believed by some biologists to be closely related to the laughing gull, from which it may have descended over the past several thousand years.

The most seagoing of all gulls, kittiwakes are decidedly not rare. In December 1973, for example, a birder by the name of William Townsend enumerated exactly 10,052 of these white-bodied, gray-winged gulls offshore of the town of Eastport, Maine. Kittiwakes are so well-adapted to life at sea that they sometimes appear hesitant to take up a landlubber’s existence during breeding season. But breed they do, gathering mud and grass to form a cup-shaped nest to contain their two eggs securely on the cliff’s face. Unlike other gulls, kittiwakes don’t recognize their young until they are several weeks old. On tiny ledges, the chicks are unlikely to wander, so there’s no need for the parents to be able to identify them. Adapting their habits to an ever-changing world, kittiwakes have even learned to nest on ledges of buildings in Britain.

Though gulls might appear to be in no short supply today, many of their populations suffered over-hunting during the 19th century. By the end of that century, untold thousands of gull eggs had been collected for food and countless birds killed for their feathers, popular as ornaments for clothing.

For example, the great black-backed gull vanished from its breeding grounds along the Maine coast, and egg collectors severely plundered the nests of Western gulls on California’s Farallon Islands, bringing about a population crash. Herring gulls declined so radically that they reportedly disappeared from parts of Rhode Island, while in turn-of-the-century photographs of a Cape Cod fishing fleet, nary a gull appears.

Eventually the birds gained protection, and their numbers have since escalated, thanks in part to ever-growing landfills and other human activities that offer an easy supply of food for the indiscriminate eater. Now gulls may even sometimes seem like a nuisance, flocking above fishing boats, snatching garbage from Dumpsters, and resting on freshly cleaned yachts.

But no doubt the gull, at once mundane and remarkable, will always endure as a symbol of the sea.

By Ocean Navigator