All About Seagulls - Gulls and Kittiwakes
A Family of Birds Concentrated Along Northern Coastlines
Jun 10, 2009
Human communities tend to be built near sea coasts and lake shores, and this is also where gulls spend most of their lives, which explains why almost anyone living in the northern hemisphere can recognize a gull. (Gulls do occur in the tropics but they are much less common south of the equator). Typically white breasted with darker backs, they soar and glide high above, and their rather harsh calls are associated with coasts and offshore waters. Most belong to the genus Larus, which comes from the Greek word laros, meaning “a sea bird,” though not all live near the sea.
What Do Gulls Eat?
Gulls typically eat fish and other aquatic life including mollusks (clams, snails etc.), and invertebrates such as worms and insects. Their diet also includes a wide range of other foods including small animals, eggs, berries and other plant material, and edible items discarded in human garbage.
Gulls generally feed at the surface of the water without diving. (Kittiwakes and a few other gull species plunge dive after prey). Far offshore, they congregate where food is plentiful—along the continental shelf, where cold water upwellings bring food from the ocean depths, or where dead animals and whale feces are floating on the surface.
On land, gulls rob nests, even those of their own species, for eggs and young, feed on carrion, and some species visit landfill sites and ploughed fields.
Gull Breeding and Nesting
Gulls usually gather in large flocks to breed and frequently mix with flocks of other sea birds. They are monogamous (have only one mate), and build nests in shallow scrapes on the ground lined with vegetation. (Some also nest in trees, or on cliffs. Species that tolerate humans well, such as the Black-headed Gull, will nest on rooftops or chimneys.)
The female lays two or three eggs, which the pair incubates in turns for three to five weeks. The young are capable of moving around soon after hatching and, particularly in colonies of larger gulls, are at constant risk of being captured and eaten by other gulls. Chicks fledge at three to seven weeks, but their parents may continue to feed them for several more weeks.
Interesting Gull Behavior
Gulls may seem ordinary to many people but there are some interesting things about them:
- Even after breeding colonies disperse, gulls flock together to feed, bath, and roost. Flocks prefer flat open spaces.
- They store swallowed food in the crop and typically go to roost with a crop full of food, which they digest while resting. Indigestible items are regurgitated as pellets.
- Nesting adults sometimes steal young from nearby nests to add to their own nests.
- Most gulls are not migratory, remaining in the same place all year; however, their daily habits and seasonal movement can be very predictable. Birds that live in the far north regularly migrate south during the coldest months of the year.
- Gulls have a tendency to wander off course and are frequently identified outside their normal range by birders.
- Because of a wide variation in plumage within species, and a tendency to mix with flocks of other species, gull identification can be particularly tricky.
- A gull can live up to thirty years.
History of Gulls
When we see the large flocks of seagulls about today, it’s hard to believe that some species were once hunted almost to extinction. They were taken for feathers and food, and eggs were collected for food as well.
In the 1920s both Canada and the United States passed laws to protect gulls and the birds recovered - in fact, species such as the Herring Gull did so well that their numbers soared to unnaturally high levels. Large flocks of gulls feeding on the waste from fisheries and food sent to landfill sites competed with other sea birds, such as terns, plovers, and puffins, for nesting sites, causing population decreases in those species.
Today, with the collapse of fisheries and many municipalities doing a better job of composting and recycling, gull numbers are dropping again. Other factors, such as oil spills and pollution pose a threat to all gull species. Six of the fifty-one gull species are listed as vulnerable, and other species may be declining rapidly.
Sources:
Firefly Encyclopedia of Birds. Perrins, Christopher ed. Buffalo: Firefly Books, 2003
Latin Names Explained. Gotch, A. F. New York: Facts on File, 1995.
Smithsonian Field Guide to the Birds of North America. Floyd, Ted. New York: HarperCollins; 2008.
The Sibley Guide to Birds. Sibley, David Allen. New York: Alfred A. Knopf, 2000.
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