Herring Gull

Photo: Robert McCaw

The seashore would not be the same without seagulls, but to gulls the coast is just one place to make a living. Gulls also range inland beside lakes and rivers and on garbage dumps and golf courses. In Canada, they are found in every province from the Atlantic Provinces to British Columbia.

Through most of its Canadian range and in the northeastern United States, the Herring Gull (Larus argentatus) is the most numerous of all gulls.

However, on the west coast the closely related Glaucous-winged Gull (Larus glaucescens) is more common, and on the Great Lakes, the smaller Ring-billed Gull (Larus delawarensis) is more abundant.

Relation to human beings

At the end of the nineteenth century gulls were rare along the Atlantic coast. In those years, many farmer-fishermen led a difficult life on outer islands tending gardens, fields, and flocks, and fishing with nets and lines. Any bounty from the sea was welcome, and gull eggs and young were worth considerable exertion. Additional pressure on gull populations resulted from millinery trade demand for bird feathers, which were fashionable decorations on ladies' hats.

The 1900 census showed fewer than 4000 herring gull pairs--all in New Brunswick and eastern Maine. However, in 1965, censuses showed about 100,000 pairs on 240 colonies along the shore from New York City to Grand Manan, New Brunswick. Censuses on 10 bird sanctuaries on the north shore of the Gulf of St. Lawrence showed an increase from 1000 herring gulls in 1925 to 18,000 in 1965, although the population has since stabilized.

There were several reasons for this dramatic increase. As the standard of living rose and the use of inboard engines spread, fishermen gathered into coastal villages at safe harbours, leaving the outer islands to the thunder of the surf and the cries of the seagulls. And from 1916 Herring Gulls were protected by the Migratory Birds Treaty between Canada and the United States. Most important, perhaps, was the gulls' readiness to exploit new food sources provided by human waste. In many places these scavengers doubled their numbers every 15 years. Now they are a nuisance in some metropolitan areas and are a potential hazard to aircraft flying in and out of airports.

But not all human activities have been beneficial to Herring Gulls; in the early 1970s the levels of pollution in the lower Great Lakes were found to be causing reproductive failure of this species. Similar failures had occurred in the mid sixties on Lake Michigan. Detailed studies showed that behavioural alteration and embryonic mortality were responsible, and that high levels of organochlorine compounds (polychlorinated biphenyls, DDT-related compounds, mirex) were present. A monitoring program on the Great Lake was set up by the Canadian Wildlife Service in conjunction with the International Joint Commission. By the end of the 1970s residue levels had decreased significantly and reproduction was back to close to normal levels.

Appearance

The adult Herring Gull is about 610 millimetres from bill to tail and has a white head, body, and tail. Its bill is yellow with a red spot on the lower tip and its legs are flesh-coloured. Adult gulls have grey backs and upper wing surfaces, and the tips of their outermost flight feathers are black with a white spot. In winter, adult heads are streaked with brown. Immature birds are a mottled brown and take four years to develop full adult plumage.

Nesting habits

Herring gulls nest in colonies and, once a colony is well established, they are faithful to it and reluctant to settle elsewhere. Yet as the colony grows some birds are unable to establish breeding territories. Sooner or later, these birds start to loaf near abundant food supplies. As the urge to breed grows, some start nesting and the rush is on. In a very few years, the colony grows to capacity.

The distance between nests in a colony varies and depends on the terrain and the availability of nest sites and on the food supply nearby. Where Herring Gulls share the colony with other colonial seabirds, such as puffins, the gulls' nests are well spaced out. Each pair defends the area of the puffin colony around their own nest, from which they steal the puffins' eggs and rob fish from the adult puffins. Elsewhere, if the food supply is not readily defensible, as is the case with garbage dumps situated some distance from the colony, birds nest closer together. This enables them to take concerted action when a predator appears.

Herring Gulls will nest in a variety of sites. On off-shore islands they frequently occupy flat ground but on the mainland they tend to nest on cliffs, probably to avoid predatory mammals. In some places where food from human activities is very abundant, they have begun to nest on roofs and window ledges of buildings. The nest is a circular scrape lined with moss or grass which is also used to build up the rim. On cliffs they tend to nest on turf-covered ledges which allow them to form a depression, avoiding the bare rock.

Breeding

Courtship begins as soon as birds arrive at the colony in the spring. Once pairing has taken place the birds form a nest scrape or, more often, re-furnish an old one. By mid May, in most areas, a clutch of three eggs has been laid and incubation begins.

Females laying for the first time, usually in their third or fourth year, often lay only one or two eggs. They also tend to lay later in the season than more experienced birds, which make up about 75 percent of the breeding population.

Eggs are well looked after, but they can be lost, e.g. eaten by other gulls or washed away by storms. Birds that lose their eggs early in the season will usually lay a replacement clutch. The greatest losses in the colony are usually to tiny chicks in the first few days after hatching. In one study, each pair produced an average of one chick a year, ready to leave the colony at 40 60 days of age. However, about one-third of those chicks died before another month had passed because they could not fend for themselves.

Behaviour

Although at first glance a Herring Gull colony seems a noisy, squabbling anarchy, there is a roughhewn organization. Each pair occupies an area from which they drive other gulls and on which they nest.

Herring Gull communication has been studied for several decades. A gull states intent to stand fast by giving the trumpeting "long call". It threatens to peck a neighbour by drawing itself up to look bigger, lowering its bill-tip ready to strike, and pulling its "wrists" out of its body feathers. Then it steps stiffly towards its opponent.

The Nobel prize-winner Niko Tinbergen and his students have studied the way that the behaviour of the Herring Gull relates to the survival of individual birds. They have observed that during incubation the parent gulls are extremely solicitous of their eggs, turning them gently with their bills from time to time to ensure even development of the embryos. But after hatching the gulls immediately remove the broken eggshells, the white inner surface of which might attract predators. Apparently the encounter of the bill with the jagged edge of the broken shell stimulates the adult to grasp and fly off with it.

This task occupies only a minute of the adults' time once a year and yet every bird performs it. Tinbergen also observed that the sight of the parent's bill stimulated the newly hatched chick to peck at it. In response the adult (whether experienced or not ) regurgitated food. By using models of the adults' head, Tinbergen showed that chicks pecked more vigorously at a bill with the normal red spot near the tip than one without it. They also responded more vigorously to a long thin bill than to a short one. In fact, a pencil, longer and thinner than a real bill, elicited the most vigorous pecking.

When they start to run about, chicks do not know the borders of their parents' territory, and the adults have to guard them against neighbours who would kill trespassers. Spots on the top and back of the chick's head identify each chick individually; the adults learn these markings in the first few days. These spots are the last of the downy plumage to be lost.

When the Herring Gull population is dense, gulls will occupy all suitable places in their feeding area (as distinct from the colony). Adults on feeding areas drive away intruding gulls. If the fledglings, already at a disadvantage because of their inexperience, were excluded, their survival would obviously be endangered. However, chicks can lessen the adults' territorial aggressiveness on the feeding areas by assuming a hunched posture, pumping their heads and voicing shrill calls. The same behaviour caused parents to feed their chicks on the breeding colonies. Such adaptations reduce the mortality of chicks at the times when they are most vulnerable.

Feeding habits

How do the Herring Gulls from a colony get all the food they need to sustain themselves and raise their young? In 1961 and 1962, near Boston, Massachusetts, breeding gulls were caught and coloured several bright tints to trace their daily trips for food. The vast majority of the gulls sought their food as close as possible to their breeding colony. If there was a fish pier within eight kilometres, few gulls went farther. If the nearest dump was 27 kilometres away, commuting that far was regular; even 40 kilometres was not an unreasonable daily round, if there was nothing nearer and the rewards were attractive enough.

After the gulls left their islands in mid or early August, some drifted south along the coast and a kaleidoscope of gulls was reported at loafing areas such as points on Cape Cod where gulls could go several directions to follow fishing boats. The dumps of Greater New York and resort towns of the New Jersey coast reported them too; but studies of the proportions of marked to unmarked birds made in July-August and again in January-February showed that most of the adult gulls stayed near home. Once they have begun to breed, they apparently tend to winter next door.

Examination of the food in Herring Gulls' stomachs shows that they will eat almost anything: clams, small fish, floating dead animals, young and adults of other nesting birds, bread, French-fried potatoes, and so on.

Individual Herring Gulls tend to specialize in particular types of food or feeding techniques. Within a large colony some birds may regularly visit dumps, while others may feed entirely on fish and crabs found on the seashore. A few individuals take to cannibalism, watching their neighbours for an opportunity to sneak in and remove an egg or chick. These birds are often breeders which have lost their own brood. Although large numbers of Herring Gulls in North America are almost entirely dependent on human activities for their food, there are still populations breeding on offshore islands or in remote parts of the low Arctic which exist on a natural diet.

Related species

Of the 43 species of gull found in the world, 15 breed in Canada. Specialized feeding techniques and variation in range prevent competition between species.

Black-backed Gulls, found only on the Atlantic coast, are powerful fliers off-shore. Ring-billed Gulls feed more on food taken on land than do Herring Gulls. Laughing Gulls are strong fliers, hovering, parachuting, and picking from the surface; their breeding range lies mostly south of the herring gulls'. Bonaparte's Gulls are faster, more erratic fliers, picking small prey from the water or sitting and pecking like chickens. They nest in trees in the forests northwest of the breeding range of the larger gulls. The cliff-nesting Iceland Gull occurs in the northern part of the herring gull range, coming south in winter to the coasts of the Atlantic Provinces. Thayer's Gulls nest in the Arctic and winter in coastal British Columbia. In the far North are cliff-nesting glaucous gulls. Even farther north, on the arctic islands and northern Greenland, there are species such as Sabine's Gull, Ivory Gull, and Ross' Gull which southern Canadians seldom see.

Reading list

• Darling, L. 1965. The gull's way. Wm. Morrow and Co. New York.
• Godfrey, W. E. 1966. Birds of Canada. Queen's Printer. Ottawa.
• Graham, F., Jr. 1975. Gulls. A social history. Random House, New York.
• Russell, F. 1964. Argen the gull. McClelland and Stewart. Toronto.
• Tinbergen, N. 1953. The herring gull's world. Collins. London.

	Canadian Wildlife Service - Hinterland Who's Who series Last update: 19 January 1999 Copyright © 1999, Environment Canada. All rights reserved.
Reproduced with permission of the Minister of Public Works and Government Services Canada, 1999.