“It is the access to food that determines where seabirds are to be found. In the ocean, production is greatest in the North. That is why that area has the greatest number of seabirds,” explains Robert T. Barrett, professor at the scientific section at UiT Arctic University of Norway. Barrett is also a member of SEAPOP, a collaborative effort to monitor and map seabird populations in Norwegian waters.
There are fifty-seven seabird species in Norwegian waters. They are divided into the two main groups: “endemic” and “periodic” seabirds.
Endemic seabirds live at sea or along the coast the year round. Procellariiformes, gannets, cormorants, terns, and all auks belong to this group, as do several gull species and some of the duck species, such as the common eider.
Periodic seabirds live at sea or along the coast only during certain times of the year. Examples of such seabirds include certain ducks, such as the long-tailed duck, the common scoter, and the velvet scoter, which breed inland but migrate to the coast to winter.
It is the access to food that decides where seabirds are located. Their habitats can be divided in two: breeding areas and wintering areas.
The location of breeding areas is determined by two factors: safe spots for nesting, and adequate access to food during the breeding period.
Wintering areas are determined by where there is access to food during the autumn and winter.
Smaller local colonies of gulls, terns, and cormorants can be found along the entire Norwegian coast. They breed among the skerries and find food in shallow waters and the shoreline.
SEAPOP (an acronym for SEAbird POPulations) began as a comprehensive, long-term programme for monitoring and mapping Norwegian seabirds in 2005, with a particularly watchful eye on population trends. The project emphasizes models that show how human activity affects the seabird populations, so that such population changes can be distinguished from population changes caused by natural variation.
SEAPOP is organized by the Norwegian Institute for Nature Research (NINA), the Norwegian Polar Institute (NP), and the Tromsø University Museum (TMU). The programme is funded by the Ministry of Climate and Environment (KLD), the Ministry of Petroleum and Energy (OED), and the Norwegian Oil and Gas Association.
You can find SEAPOP’s webpage here (in Norwegian)
But the major seabird populations are found in bird cliffs. Except for Runde, all of the Norwegian bird cliffs are located north of the Arctic Circle. The distance to the so-called Eggakanten – the slope from the continental shelf down to the deepest parts of the Norwegian Sea – partly determines where bird cliffs are possible. It is in the upwelling areas along Eggakanten that enough food is produced to supply the bird cliffs with enough food for the chicks. Storegga, around 70 km off of Sunnmøre in Western Norway, is close enough for the birds to fly there to look for food for their chicks at Runde. Farther north, Eggakanten lies too far out to sea, and it is not until at Lofoten and Vesterålen that Eggakanten again is close enough to land.
During summer, access to light and nutrients stimulates the production of food in the Barents Sea and at Svalbard. This is why large bird cliffs are also found there.
When the birds are not nesting in the bird cliffs, they spread far and wide across the ocean. Some, like the terns, winter far away from Norway, while others winter in Norwegian waters. Some species migrate to Norway to winter, for example the king eider and Steller’s eider, which breed in Russia but winter in Varangerfjorden in Finnmark.
Several of the seabird species, particularly along the Norwegian mainland, have been greatly reduced. It has been estimated that the number of common murre pairs breeding along the Norwegian coast is only 10 per cent of the population in the 1960s. For other species, such as the great cormorant, the population size is stable.
The tendency is clear: the farther north, the more seabirds there are. More than half of Norwegian seabirds breed in Bjørnøya and Svalbard (3 million breeding pairs out of a total of 5.5 million breeding pairs in Norway). Only 2.5 per cent of the seabirds (133,000 pairs) breed along the Skagerrak and North Sea coasts.
Hunting and egg-gathering previously represented a major threat to seabirds, with such activities for example wiping out the “Nordic penguin”, the flightless great auk, in the mid-1800s. By-catch in nets also reduced the seabird populations, including for the common murre along the Norwegian coast. Hunting and egg-gathering are not a major threat today.
Nonetheless, seabirds face many dangers.
“Threats against seabirds are a complicated issue,” Barrett says. “We don’t know what kills the greatest number of seabirds.”
Climate changes alter the ocean temperatures, something that affects the ocean’s food production. Birds still lose their lives in nets, lines, and other fishing gear. Human overfishing can reduce the food available to them. Pollutants that accumulate in the ecosystem end up in seabirds. Bits of plastic that they think is food can choke them or lead to their starvation. Oil spills kill the birds by destroying their protective layer of feathers. Future offshore wind turbines might also be a new threat.
As yet, it is unclear whether it is acute disasters such as oil spills or the chronic, invisible danger that pollutants and plastic represent that kill the greatest number of seabirds.
Wildlife changes also affect the seabird population. For example, dislocated minks take eggs and chicks, while an increased sea eagle population leads to seabirds being scared up from their cliff nests, making it easier for gulls to snatch away eggs and chicks.