The total number of seabirds breeding in the Norwegian parts of the Norwegian Sea was recently estimated at 1 270 000 pairs, of which 870 000 pairs of 20 species were breeding along the mainland coast and 400 000 pairs of 15 species were on Jan Mayen. Most populations have decreased steeply over the last decade (mean trend −5.8% year−1 in 2005–2015), and many have decreased almost constantly since monitoring started three to five decades ago (see e.g. Figure 13).
No single factor explains all these trends; however, long-term breeding failures for species feeding in pelagic waters such as Atlantic puffin Fratercula arctica, black-legged kittiwake Rissa tridactyla, common guillemot Uria aalge, and Northern fulmar Fulmarus glacialis indicate that much of the problem along the mainland coast is related to drastic changes in the availability of 0-group fish (especially herring), and also linked to variations in ocean climate.
Figure 13: Development in the breeding populations of black-legged kittiwake, common guillemot, and Atlantic puffin in the Norwegian part of the Norwegian Sea in the period 1980-2013.