The Faroe Islands (61N and 7W) consists of 18 small islands located approx. 300km North-West of Shetland and approx. 500km South-East of Iceland on the Iceland-Scotland ridge and are surrounded by highly productive seas supporting large colonies of seabirds (Gaard et al., 2002).

Black-legged kittiwakes breeding success data is from “Høvdin” on the island Skúvoy (61.78N and 6.85W) which is the main long term study area for this species on the Faroe Islands. Atlantic puffin  breeding success data is from the largest puffin colonies on the Faroe Islands “Lamba” and “Dalurin” on the island Mykines (62.10N and 7.65W). Tern reproductive success data and Common guillemot, Arctic tern Sterna paradisaea (hereafter tern) and kittiwake population trend data are from nationwide surveys.

In the context of this project focus will be on Black-legged kittiwake, Atlantic puffin and Arctic tern breeding success as well as population trends for Common guillemot, Black-legged kittiwake and Arctic tern.

The productivity of a subsample of kittiwake nests (1,050 nests on average) at the study site Høvdin was monitored from 1982 to 2001. After 2001 all the area has been monitored annually counting total number of adults, nests and chicks late in the breeding season (Hátún et al., 2017) (Fig. 4.1). Population size and productivity of terns has been monitored annually nationwide with the aid of a citizen science scheme since 2003 (Olsen & Sørensen 2022) (Fig. 4.1 and 4.3) and puffin reproductive success has been monitored annually since 2011 at study sites Lamba and Dalurin on the island Mykines as part of a RAMSAR monitoring scheme (Fig. 4.1). Nationwide surveys of guillemots and kittiwakes were done in 1972, 1987, 1997–1999 and 2007–2014 (kittiwake surveys started in 1987) (Fig. 4.2).

Figure 4.1 Reproductive success of Black-legged kittiwake at Høvdin, Atlantic puffin on Mykines and Arctic tern nationwide on the Faroe Islands.

Kittiwake and tern reproductive success was measured as chicks per nestnest (kittiwake) at the study site Høvdin and average chicks perpair peryear (tern) throughout the whole country while that of the puffin reflects the proportion (%) of burrows that contained a chick each year at Lamba and Dalurin study sites on Mykines.

Figure 4.2 Guillemot and kittiwake population trends on the Faroe Islands.

The guillemot population declined by 68% from 1972 to 2014 while the kittiwake population declined by 60% from 1987 to 2014. Interestingly a ban on hunting guillemots during summer came into effect in 1980. Prior to this, guillemots were primarily hunted during summer. The law was adjusted in 1987, 1988 and 1989 in order to shorten the hunting period and has not been changed since. The current hunting period is from 1 October to 20 January. Interestingly there was a steep population decline until the 1980s after which even though the decline continues it is at a much lower rate. The kittiwake population has also declined massively and follows quite well the guillemot decline since the 1980s. Kittiwakes were hunted in the past but never to the same extent as guillemots. Since there are no requirements for hunting statistics for any species on the Faroe Islands there is no publicly available hunting statistics which makes it very difficult to say what effect hunting has had on these species.

Figure 4.3 Mean number of terns on the Faroe Islands from 2004 to 2023.

Although the number of terns observed on the Faroe Islands can vary quite a lot from year to year and despite that there have been some years with a relatively large number of terns there is an overall declining trend since 2004 when monitoring started. 

By combining the so-called 0-group from the main fish species cod, haddock, Norway pout and sandeel, representing more than 90% of all juvenile fish on the shelf during late June surveys, Jacobsen et al. (2019) developed a 0-group index which, with the exception of a few years, offered a convincing explanation for the variation in kittiwake reproductive success at the monitoring site, Høvdin. The 2009 and 2017 peak in tern reproductive success as well as mean number of terns throughout the country closely follows the kittiwake reproductive success these years and it is therefore also likely that these peaks can be explained at least partly by the 0-group index. The same is true for puffin reproductive success except in 2019 where puffins breeding success was as good as in the peak year 2017 which means that the puffins were still able to find plenty of prey even though both kittiwakes and terns were having a bad year. When comparing the abundance of 0-group fish larvae from sandeel (Ammodytes marinus), cod (Gadus morhua), haddock (Melanogrammus aeglefinus) and Norway pout (Trisopterus esmarkii) with the reproductive success of Atlantic puffins on Mykines, it is clear that the 0-group abundance of all four fish species was very low in 2019.

Figure 4.4 0-group abundance of sandeel, cod, haddock and Norway pout (left axis) and Atlantic puffin (AP) reproductive success on Mykines, Faroe islands (grey line, right axis).

As previously mentioned elsewhere in this report large-scale oceanographic variability is an important driver of the productivity of Nordic shelf ecosystems. The Subpolar Gyre (SPG) and Modified East Icelandic Water (MEIW) bring nutrient-rich water into the Northeast Atlantic which affect the productivity of keystone species of plankton and fish and in turn also seabirds on the Faroe Islands (Hátún et al. 2017; Jacobsen et al. 2019; Olsen et al. in prep). To what extent this effect continues on to e.g. the Norwegian shelf is unknown but interestingly there is a strong correlation between Atlantic puffin reproductive success on Mykines and the mass of zooplankton in the Norwegian sea in May (g/m²) from 2011 to 2020 (r² = 0.74) (Fig 5) maybe indicating that there is a common underlying driver capable of causing production peaks on both the Faroe and Norwegian shelves.

Figure 4.5 Atlantic puffin reproductive success (red line, left axis) and mass of zooplankton (blue line, right axis) in the Norwegian sea in May (g/m²) from 2011 to 2020.

Even though the focus in this project is on reproductive success we chose to include population trends for the species where nationwide data was available. This is to shed light on the fact that even though there seem to be relatively large peaks in reproductive success some years for all the seabird species monitored these peaks are clearly not enough to sustain the populations which have decreased since monitoring began, sometimes as much as 70% the last 50 years.

Among the biggest knowledge gaps and thereby uncertainties regarding drivers of reproductive success and population trends are the lack of data on what adults are feeding on, both during and outside the breeding season. For many species and most populations, very little is known about where the main feeding areas are, not least during the breeding season. It is however clear that the most important prey for adult survival and a successful breeding season for the various species can vary considerably between species and even for the same species in different areas.

It is also crucial that further research focuses on the effect of human activities, not least on e.g. the effect non-sustainable fisheries has on the availability of suitable prey, both during the breeding and non-breeding season. 

Jacobsen, S., Gaard, E., Hátún, H., Steingrund, P., Larsen, K. M. H., Ólafsdóttir, S. R., & Poulsen, M. (2019). Environmentally Driven Ecological Fluctuations on the Faroe Shelf Revealed by Fish Juvenile Surveys. In Frontiers in Marine Science. https://doi.org/10.3389/fmars.2019.00559

Gaard, E., Hansen, B., Olsen, B., & Reinert, J. (2002). Ecological features and recent trends in the physical environment, plankton, fish stocks, and seabirds in the Faroe shelf ecosystem. In Large Marine Ecosystems (Vol. 10, pp. 245-265). Elsevier.

Olsen, B and Sørensen, S (2022). Fuglurin rímir úr Vestmannabjørgunum. In Sjóvarmál 2022. ISBN 978-99918-890-1-6

Hátún, H., Olsen, B., & Pacariz, S. V. (2017). The Dynamics of the North Atlantic Subpolar Gyre Introduces Predictability to the Breeding Success of Kittiwakes. Frontiers in Marine Science, 4(123). https://doi.org/10.3389/fmars.2017.00123