Boobies and Gannets: Sulidae

Physical characteristics: The northern gannet is the largest of the three species of gannets. Its feathers are mostly white, with a light rusty color on the back of its head. Northern gannets are between 34 and 39 inches (87 and 100 centimeters) long from their beaks to the end of their tails, and their wingspan is 65 to 70.9 inches (165 to 180 centimeters). Young gannets are mainly dark brown, with feathers gradually lightening until they get their white adult feathers in their fourth year.

Geographic range: Northern gannets breed on offshore islands in the northern Atlantic Ocean. In winter they move south to warmer waters along eastern North America and western Europe and Africa. Some spend the winter in the Mediterranean Sea.

Habitat: Most northern gannets breed on cliffs or flat ground on offshore islands, but some also breed along the rocky shores of continents. When they are not breeding, they spend the rest of the year flying over the ocean, sitting on the water, or diving in to catch fish.

Northern gannets nest very close to each other, but avoid fights by using displays that tell other birds to stay away. (© Hugh Clark/Photo Researchers, Inc. Reproduced by permission.)

Diet: Northern gannets are seabirds that feed mostly on schools of small fish such as herring. They usually plunge-dive headfirst into the ocean, sometimes from more than 100 feet (30 meters) above the water. Just before entering the water, they fold their wings backward alongside their bodies for a smooth entry. Gannets often hunt in big groups of as many as 1,000 birds. Sometimes northern gannets follow fishing boats and snatch the fish parts that are tossed into the water.

Behavior and reproduction: These birds usually stay with their partners for life, and they meet every year at the same nest site. When they meet, they greet each other with many different courtship displays. For example, they stand face to face with their wings out. Then they knock their bills together and bow to one another.

The birds make flat nests of seaweed and grass glued together with their droppings. The nests are crowded together, but they are spaced just far enough apart so that the birds can't peck each other. Each female lays one egg, and both parents care for the chick. The young bird grows amazingly fast, and by the time it is two months old, it may weigh 50 percent more than its parents. At the age of three months, the chick jumps from its nesting ledge after its parents desert it. The young northern gannet stays at sea the first three years of its life, coming to land only to breed.

Northern gannets and people: Humans used to take chicks for food, but in most places that has stopped. Northern gannets attract a lot of birdwatchers because of their huge nesting colonies and their amazing skill at diving.

Conservation status: Northern gannets are not in danger of extinction. Fishing boats that take large numbers of fish in areas where gannets feed are a threat to the birds. ∎