Three species of seabirds feeding in the pelagic part of the ecosystem were selected as indicator species for the eastern part of the Norwegian Sea: the black-legged kittiwake (
Rissa tridactyla, hereafter kittiwake), Atlantic puffin (
Fratercula arctica, hereafter puffin), and common guillemot. These species were selected because they feed in different parts of the pelagic ecosystem. Time series of their population development in the eastern Norwegian Sea were derived from their estimated breeding numbers in 2013 and annual monitoring of trends in selected breeding colonies (Runde, Sklinna, Røst and Anda (only kittiwake and puffin).
The breeding population of kittiwakes in the eastern Norwegian Sea has declined by 78% since monitoring started in 1980. Several large colonies have already disappeared, and more risk extinction within a few decades. In the same area and period, the breeding population of puffins has declined by 75% and that of common guillemots by as much as 99%. The remaining population of common guillemots breeds in areas sheltered from predation and is currently relatively stable, but the species is at high risk of extinction as a breeding species along a large part of the Norwegian mainland coast (Figure 12).
Jan Mayen in the north-western Norwegian Sea holds only < 10,000 pairs of kittiwakes, < 5000 pairs of puffins, and < 1000 pairs of common guillemots. Common guillemot numbers have shown a declining trend since 2011, when monitoring started.
The largest changes in seabird numbers in the eastern Norwegian Sea are linked to ocean climate variability; these are most likely caused by substantial changes in prey abundance and availability, with dire consequences for reproductive success and recruitment. This has also affected survival rates to some extent, and populations can occasionally be severely hit by extreme weather events. Still, an increasing number of studies document effects of other natural and man-induced changes that may also contribute to the variation in seabird breeding performance. These include factors such as competition with fisheries and increased predation from white-tailed eagles (Haliaeetus albicilla), as well as contaminants and human disturbance.
