Brünnich’s guillemot (Uria lomvia)

Closeup of a Brünnich’s guillemot on the ocean surface.
Photo: Stein Ø. Nilsen / tromsofoto.net

Since the Brünnich’s guillemot feeds on key species in the ecosystem and is so abundant, it may be a good indicator for the productivity of the ecosystem. The Brünnich’s guillemot makes up the largest proportion of the seabird biomass in the Barents Sea (over 60%) and was Red Listed in 2010 due to the decline in its population. It is a generalist and an important predator on capelin, polar cod, pelagic amphipods and krill.

What is being monitored?

Size of breeding population

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The figure shows the trend in the breeding population of Brünnich’s guillemots in 7 selected colonies on Spitsbergen, 2 on  Bjørnøya and 3 on Jan Mayen. For each colony, the population size is shown as a percentage of the average in the colony during the entire monitoring period. The population has declined in all the monitored colonies on Bjørnøya and Spitsbergen. The decline is around 4% per year, except for Jan Mayen, where the data series are too short to allow interpretations on population size. Because of this, the Brünnich’s guillemot was listed as "Near Threatened" (NT) on the Norwegian Red List published in 2010.

Status and trend

In all, 142 colonies are known in Svalbard, with a total breeding population estimation of 615,000 pairs. The largest colonies (> 100,000 pairs) are situated in the southeastern part of Spitsbergen (Koval'skifjella and Stellingfjellet) and on Hopen and Bjørnøya. More than 80 % of the Svalbard population breeds within this "triangle".

Following a period of relative stability or increase, the breeding population of Brünnich’s guillemots has been declining by ca 4% per year since the mid-nineties. This decline has been observed in all the monitored colonies on Spitsbergen and Bjørnøya. An equivaltrend has been observed in Finnmark colonies (mainland Norway). Trends for colonies in East-Svalbard are currently unknown.

 

Causal factors

The cause of the Brünnich’s guillemot decline in Svalbard is likely connected to the warming of oceans in the species’ winter habitats near Iceland and Greenland. Here the warming most likely has led to changes in the food web and different access to prey for the Brünnich’s guillemot.

Brünnich’s guillemots are hunted in Greenland, but the hunting pressure has been decreasing since 2001. Harvesting is therefore probably not causing the recent Brünnich’s guillemot decline in Svalbard. By-catching of guillemots in fishing gear and/or oil pollution may also contribute to the decline in the population.

Consequences

All colonies of Brünnich’s guillemots monitored in Svalbard (western Spitsbergen and Bjørnøya) show signs of decline since the mid-1990s.

The number of breeding birds has declined by approximately 5% per year. This means that the average size of the Brünnich’s guillemot population has probably declined by a third in the last decade, at least on Bjørnøya and western Spitsbergen.

Brünnich’s guillemots play an important role in the ecology of Svalbard through their transport of large amounts of nutrients from the marine environment to the terrestrial environment, when they fertilize local areas of tundra with their guano (excrement). A reduction in the breeding population may thus reduce this nutrition "pump", which may have consequences for the terrestrial environment.

About the monitoring

The Brünnich’s guillemot is one of the most numerous seabirds in Svalbard, and breeds in dense colonies all over the archipelago. The diet of adult Brünnich’s guillemots is more varied than that of common guillemots. It consists mainly of fish and crustaceans, but during the breeding season, chicks are essentially fed with fish, such as polar cod (the most important prey item in Spitsbergen) or capelin (the most important prey item on Bjørnøya).

Brünnich’s guillemots are thus considered to be a good indicator of the availability of pelagic fish stocks. They are also very sensitive to oil spills and by-catching in fishing nets.

Brünnich’s guillemots have shown a drastic decline in population size all over Svalbard since the mid-1990s. The species is now red-listed in Norway (Near Threatened status).

Brünnich’s guillemots are monitored on Bjørnøya and western Spitsbergen. The size of several colonies is estimated annually in order to detect short- and long-term changes in population size. Moreover, to explain and even predict those changes, several other parameters are monitored annually. This includes the annual adult survival of Brünnich’s guillemots and the diet of their chicks during the rearing period. On Bjørnøya, the average breeding success of Brünnich’s guillemot is also estimated annually.

In each monitored colony, the total number of Brünnich’s guillemots present in some study plots is counted annually. This represents the best and internationnaly accepted method to detect changes in a guillemot colony, and thus the population size.

Places and areas

Fuglehuken is one of the largest Brünnich’s guillemot colony on western Spitsbergen. Ossian Sarsfjellet is located innermost in Kongsfjorden and is easily accessible from Ny-Ålesund. Bjørnøya has one of the largest Brünnich’s guillemot colonies in Svalbard, and the southernmost.

Relations to other monitoring

Monitoring programme
International environmental agreements
Voluntary international cooperation
Related monitoring