Northern Gannet

## Description

The Northern gannet is the largest seabird native to the coasts of the Atlantic Ocean. The males and females are similar in appearance. Adults have a mainly white streamlined body with a long neck, long and slender wings. The head and nape have a buff tinge that is more prominent in the breeding season, and the wings are edged with dark brown-black feathers. The long pointed bill is blue-grey, contrasting with black bare skin around the mouth and eyes. Juveniles are mostly grey-brown, becoming increasingly white in the five years.

## Distribution

Northern gannets breed in Western Europe, North America, and the Caribbean. Many adults migrate to the west of the Mediterranean, passing over the Strait of Gibraltar. Other birds follow Africa's Atlantic coastline to arrive in the Gulf of Guinea. Immature Northern gannets from colonies in Canada fly to the Gulf of Mexico, much further south than the adults and have been recorded as far south as Ecuador. Northern gannets spend most of the time in the ocean coming on land only to breed and raise their chicks. They nest on cliffs overlooking the ocean or on small rocky islands.

## Behavior

Northern gannets are gregarious birds that breed in large colonies and forage in groups at sea. They are fast and powerful flyers, but may also glide for hours, barely flapping their wings. Despite their speed, they cannot maneuver in flight and need to warm up before flying. They also walk with difficulty and this means that they have problems getting airborne from a flat area. They take off from the water by facing into the wind and strongly beating their wings. In light winds and high waves, they are sometimes unable to take off and they can become beached. Northern gannets forage for food during the day, generally by diving at high speed into the sea. They search for food both near to their nesting sites but also further out to sea. They forage from heights of up to 70 m (230 ft) and typically dive from between 11-60 m (36-197 ft). They dive with their bodies straight and rigid, wings tucked close to the body but angled back, extending beyond the tail, before piercing the water like an arrow. They control the direction of the dive using their wings and tail and fold their wings against the body just before impact. Gannets usually push their prey deeper into the water and capture it as they return to the surface. When a dive is successful, they swallow the fish underwater before surfacing, and never fly with the fish in their bill. Northern gannets also forage for fish while swimming with their head underwater. These are loud and vocal birds, particularly in the colony. Their typical call is a harsh arrah-arrah or urrah-urrah, which is emitted upon arriving or when challenging other gannets at the colony.

## Diet

Northern gannets are carnivores (piscivores) and fish form the bulk of their diet. They mainly feed on sardines, anchovies, haddock, smelt, Atlantic cod, and other shoal-forming species.

## Reproduction

Northern gannets are monogamous and form long-lasting pair bonds. The oldest birds usually return to the breeding colonies first. Males try to attract an available female after establishing a territory. The females will fly over the colony several times before landing. Their posture, with the neck, stretched out, tells the male that they are available for courtship. The males will then shake their heads in a similar way to when they are guarding their nest, but with their wings closed. Mated pairs engage in a fencing display when the male arrives back at the nest. The two birds stand breast to breast with wings spread and bills extended vertically. They fence and scissor with their bills rapidly, calling loudly at the same time. Fencing is interspersed with bill bowing. Nesting starts in March or April; during this time Northern gannets become very aggressive and confrontations normally occur only between birds of the same sex. The preferred nesting sites are on coastal hillsides or cliffs. If these are not available Northern gannets will nest in groups on islands or flat surfaces. Nests are made from seaweed, plants, earth, and debris from the sea. The males usually collect the materials. Nests are compact cups typically 30-60 cm (12-24 in) in height. The female lays one egg and incubates it within 42-46 days; during this time the egg is surrounded by the brooding bird's warm, webbed feet. The newly hatched chick is featherless and is dark blue or black in color. It is fed regurgitated semi-digested fish by the parents and is only rarely left alone. The adults feed their offspring for around 13 weeks, right up until the time it leaves. The chick fledges between 84-97 days old and becomes reproductively mature at 4 to 5 years of age.

## Population

### Population threats

Although Northern gannet populations are now not threatened globally, their numbers were once greatly reduced due to loss of habitat, removal of eggs and killing of adults for their meat and feathers. Today, these birds are frequently killed as bycatch in fisheries and are still hunted for food in some areas of their range.

### Population number

According to the IUCN Red List, the total Northern gannet population size is approximately 1,500,000-1,800,000 mature individuals. In Europe, the breeding population consists of 683,000 pairs, which equates to 1,370,000 mature individuals. Overall, currently, Northern gannets are classified as Least Concern (LC) on the IUCN Red List and their numbers today are increasing.

## Fun Facts

The gannets appeared about 30 million years ago. Word 'gannet' is derived from Old English ganot, meaning "strong or masculine".

Some of the old names of the Northern gannet include solan, solan goose, and solant goose. Young birds have been called "spotted booby" or "parliament goose", the former term referring to their plumage.

Northern gannets have streamlined bodies adapted for plunge-diving at high speed, including powerful neck muscles, and a spongy bone plate at the base of the bill. The nostrils are inside the bill and can be closed to prevent water entry. Birds can hit the water at speeds of up to 100 km/h (62 mph). This allows them to penetrate up to 11 m (36 ft) below the surface, and they will swim down to an average of 19.7 m (60 ft), sometimes even deeper than 25 m (80 ft).

Female Northern gannets are not only more selective than males in choosing a search feeding area, but also make longer and deeper dives and spend more time floating on the surface than males.

Northern gannets often follow fishing boats or cetaceans to find discarded or injured fish.

During foraging, Northern gannets may store fish in a branched bag in the throat.

When foraging at sea, the white color of these birds helps other gannets to identify one of their kind and they can deduce the presence of a shoal of fish by their diving behavior; this, in turn, facilitates group foraging, which makes capturing their prey easier. The color also makes gannets less visible to the fish underneath.

Northern gannets use the same nesting site each breeding season and over years, their nests can reach 2 m (7 ft) in height.

During the breeding period, Northern gannets aggressively defend their nesting territories. It is thought that they can recognize the call of their breeding partner, their chicks and birds in neighboring nests, and individuals from outside this sphere are treated with more aggression.

When Northern gannet chicks are ready to leave their nests they do that by launching themselves off a cliff and flying; this procedure is impossible to practice beforehand. If they leave the nest in bad weather they can be mortally wounded as they can be blown against the rocks. Once they leave the nest they stay at sea learning to fish and fly as their flight skills are too poor for them to return to the breeding ledges.