The distribution of seabirds in Norwegian and adjacent sea areas
Our distribution maps give you a quantitative overview of the occurrences of seabirds on the open sea at different times of the year. Choose between the 12 different species in the table and download maps (PDF) or specify your search by distribution data in the data portal! You can also read about the datasets that serve as the foundation for the development of the maps.
Species that are included in the analyses
|English||Latin||Name of variable|
|Little auk||Alle alle||ALALL|
|Common gull||Larus canus||LACAN|
|Herring gull||Larus argentatus||LAARG|
|Northern fulmar||Fulmarus glacialis||FUGLA|
|Northern gannet||Morus bassanus||MOBAS|
|Black-legged kittiwake||Rissa tridactyla||RITRI|
|Common guillemot||Uria aalge||URAAL|
|Atlantic puffin||Fratercula arctica||FRARC|
|Brünnich's guillemot||Uria lomvia||URLOM|
|Glaucous gull||Larus hyperboreus||LAHYP|
|Great black-backed gull||Larus marinus||LAMAR|
Certain species are excluded from seasons and sea areas where they were too few in number for the analyses to be conducted.
You can also retrieve maps on the distribution of seabirds on the open sea in the data portal:
• Under “Time period”, choose season (summer, winter or autumn).
• Under “Geographical selection”, choose sea area.
• Then choose desired species under “Species selection”.
• Then select “Open sea data” at the bottom.
About the maps
There are three maps for each species – one for each of the seasons. The maps are made up of 10x10 km2 grids, and show predicted abundance for the species in question based on two-step analyses (see Data analysis) of available distribution data of seabirds in Norwegian and adjacent sea areas (see Dataset). We also present, together with the maps, the uncertainty of the predictions as 95% confidence interval and standard error. It was not possible to define the confidence intervals for very low densities. It is therefore important to note that the uncertainty does not account for systematic errors resulting from differences in detection (see Methods). Conspicuous species that easily follow vessels are systematically overestimated. This is particularly the case for such species as the northern fulmar, black-legged kittiwake, European herring gull, great black-backed gull and common gull. Small, dark species that dive are probably similarly underestimated. This is particularly the case for the auks: the little auk, Atlantic puffin, razorbill, Brünnich’s guillemot and common guillemot. Therefore, the abundance estimates must be treated as indices.
Please note: SEAPOP maintains the copyright to all generated maps, and SEAPOP must be cited in the case of any reuse of these maps.
Each sea area (the North Sea, Norwegian Sea and Barents Sea) is separately analysed. This results in some discontinuity in the border areas between sea areas.
The seasons analysed are:
- Summer: April 1 – July 31
- Autumn: August 1 – October 31
- Winter: November 1 – March 31.
About the datasets
In the datasets, XUTM and YUTM represent the midpoint in each 10x10 km2 cell, given as UTM coordinates in zone 33. “Ocean” denotes sea area: NO = North Sea, NW = Norwegian Sea, BS = Barents Sea. The expected number of birds for each species is given for each 10x10 km2 cell.
Estimates for each species are given with species code in the next 12 columns. Next, the results from the “bootstrap” analyses for each individual species are given, where mXXXXX = average log10-transformed “bootstrap” estimates, seXXXXX = standard error of log10-transformed “bootstrap” estimates, ci025XXX = lower boundary for the 95 % confidence interval, ci975XXXXX = upper boundary for the 95% confidence interval, and CIXXXXX = size (range) of the 95% confidence interval.
Missing estimates are denoted as -999.
Please note: SEAPOP maintains the copyright to the datasets, and SEAPOP must be cited in the case of eventual reuse of the datasets.
- Summer: Comma delimited (CSV) or shape (SHP)
- Autumn: Comma delimited (CSV) or shape (SHP)
- Winter: Comma delimited (CSV) or shape (SHP)
Read more about the datasets that lie behind the distribution maps!
The razorbill, like the common guillemot and Brünnich’s guillemot, is a relatively large auk species that forages by diving. In Europe, the largest breeding populations are found on Iceland and in the United Kingdom. The razorbill is a more coastal species than the common guillemot and Brünnich’s guillemot. Particularly high occurrences can be found in the North Sea, off Scotland and northeast of England, but we also find razorbills along the coastline of northern Norway. As with common guillemots, a number of birds migrate to Kattegat and Skagerrak during the autumn and winter, most likely in the hunt for sprat and young herring.
The little auk is a small auk species, and most likely the most abundant seabird in the northern Atlantic. It nests in enormous numbers in high-Arctic areas, especially Greenland. In our areas, it is most abundant on Svalbard and Jan Mayen. The little auk feeds first and foremost on zooplankton, and copepods of the genus Calanus (including Calanus glacialis and C. finmarchicus) are particularly important. In winter, the little auk migrates southwards from the high-Arctic areas. In our areas, the Møre and Trøndelag coastlines appear to be important overwintering areas. However, data for this area is lacking. Better data exists for the North Sea, and relatively high occurrences of the birds are found along the Vestland coast and in Skagerrak.
The map shows the distribution of herring gulls in Norwegian and adjacent sea areas in three seasons: Summer: April 1 – July 31, Autumn: August 1 – October 31, Winter: November 1 – March 31. The upper panel shows the estimated number of birds per 10x10 km2 cell. The values are not corrected for detectability, and the values are overestimated since the herring gull is a rather conspicuous, surface-feeding bird that follows vessels. The lower panel shows the estimate uncertainty, denoted as the size of the 95% confidence interval of the estimate (0.025 percentile – 0.975 percentile). The same colour scale is used for both estimate and uncertainty. It was not possible to calculate confidence intervals for areas with very low occurrences, and estimate uncertainty is therefore lacking for these areas.
The northern fulmar is a very common pelagic surface-feeding bird in Norwegian waters. We find it in large numbers at all times of the year in all of our sea areas, often a little off the coast. In spite of its abundance, the breeding population on mainland Norway is modest, with only 7000-8000 breeding pairs. Conversely, it breeds in large numbers on Iceland, Svalbard, the Faroe Islands, and in the United Kingdom. The northern fulmar moves over large sea areas, also in the breeding season, and lives of food that it finds on the sea surface. Its diet includes squid, fish, zooplankton, jellyfish, cadavers of marine mammals, and fish waste. The northern fulmar often follows fishing vessels and can eat large quantities of fish offal.
The northern gannet is a pelagic seabird that forages by diving for fish which it catches 0-10 m below the sea surface. A large portion of the European population breeds in the United Kingdom, and only a few thousand pairs breed in Norway. The northern gannet has increased its numbers since the 1970s and has established many new colonies in Norway. We find the highest concentrations of the species in the western part of the North Sea, but in the autumn and winter we also find high densities off the Vestland coast.
The black-legged kittiwake is a small, pelagic seagull species that forages on the sea surface. Like other surface-feeding seabirds, it is often found together with marine mammals and diving seabirds (such as razorbills, common guillemots and Brünnich’s guillemots) which chase small fish and krill up towards the sea surface. The black-legged kittiwake signals to passing seabirds and seabirds in the neighbourhood that there is “food to be had” by its characteristic manner of circling over concentrations of food on the sea surface. This kind of interaction between different seabird species influences how the seabirds are distributed, and the interaction probably also influences the birds’ ability to find food. In the North Sea, both the black-legged kittiwake and Atlantic puffin are key species in this interaction. The black-legged kittiwake breeds in large numbers in Norway and on Svalbard, and, like the northern fulmar, the black-legged kittiwake is found in all Norwegian sea areas in all seasons. Telemetry studies suggest that black-legged kittiwakes from European colonies overwinter to a large extent off Newfoundland in Canada. This does not corroborate with our analyses here. We do not find any large reduction in the abundance of black-legged kittiwakes in our waters during the winter.
The common guillemot is an abundant seabird in the North Sea. The majority of the North Sea population breeds in the United Kingdom and on the Faroe Islands. The total population on the British islands is estimated at 1.4 million individuals, and this population has been increasing over the last 50 years. Generally, we find the largest concentrations in the western North Sea, but in the autumn and winter we also find high concentrations in Skagerrak and Kattegat. A large portion of these overwintering seabirds are young birds. Kattegat and Skagerrak are important nursery areas for herring and sprat that are important food sources for common guillemots overwintering in this area. The population of common guillemots in the Barents Sea decreased dramatically in the mid-1980s, and the population is still historically low. The occurrence of common guillemots in the Barents Sea is therefore relatively low compared to in the North Sea. In the Barents Sea we find common guillemots primarily in the southern areas along the Finnmark coast and around Bear Island. During the autumn we find relatively high occurrences in the southern part of the Barents Sea.
The Atlantic puffin is a character species and one of the most abundant seabirds along the coast in northern Norway. Approximately 900 000 pairs breed along the coast from Andøya to Vardø, and 800 000 pairs breed along the Nordland coast. Herring fry and cod fry that drift northwards in the coastal current from the large spawning grounds along the Norwegian coast are a staple diet for these colonies. In the autumn, large numbers of Atlantic puffins migrate to the southern part of the Barents Sea. This is the end point for the fish fry drift, and it is likely that fish fry are still an important part of the diet during this period. In the winter, Atlantic puffins can be found in the southern part of the Norwegian Sea. However, data from this area for this period are fragmentary, and the data uncertainty is therefore relatively large. In the North Sea, we find colonies of Atlantic puffins along the coastline of the United Kingdom and the Faroe Islands. In these colonies, the small sandeel is an important source of food. To a large extent, the distribution of Atlantic puffins in the North Sea reflects the western distribution. In the winter, the density of Atlantic puffins in the North Sea is relatively low, and parts of the population appear to migrate out of this sea area.
Together with the little auk, the Brünnich’s guillemot is the most abundant seabird species in the Barents Sea, with ca. 1 250 000 breeding pairs. It is a northern species and breeds in relatively few numbers along the Norwegian coast and the Kola Peninsula, but is abundant on Svalbard and Novaya Zemlya. In the autumn, we find them in large numbers in the central and northern parts of the Barents Sea where they feed on krill, amphipods, capelin and polar cod. Telemetry studies and banding studies from Svalbard suggest that at least certain parts of the population migrate to the north-western part of the Atlantic in the winter. In particular, the sea area between Greenland and Canada appears to be important. However, from February and through spring, we find large numbers of Brünnich’s guillemots again in the southern part of the Barents Sea, where they follow the spawning runs of capelin in towards the coast of Norway and the Kola Peninsula.