Black-legged kittiwake (Rissa tridactyla)

Closeup of two black-legged kittiwakes sitting in a rock formation. A lot of ocean in the distant background.
Photo: Stein Ø. Nilsen / Norwegian Polar Institute

The kittiwake obtains its food on the surface and hence functions as an indicator for this part of the marine ecosystem. This pelagic gull comprises a large proportion of the sea birds, in terms of both biomass and food consumption, and is dispersed over the whole of Svalbard and the rest of the Arctic.

What is being monitored?

Population size on Bjørnøya and Spitsbergen

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For each colony, the population size is shown as a percentage of the average in the colony during the entire monitoring period. The kittiwake population in Svalbard and on Bjørnøya declined in the years prior to 2002–2003. It has since recovered in some of the colonies, while others are still declining. It has subsequently recovered in all the monitored colonies. The population in Svalbard has remained relatively stable over the entire monitoring period taken as a whole.

 

 

 

Status and trend

The Svalbard population of black-legged kittiwakes has probably increased during the last century, but most colonies in the Atlantic and Pacific oceans are declining. In Svalbard most of the monitored  colonies  on Bjørnøya and Spitsbergen  remain stable or are even increasing slightly, after a period of decline during the 1990s. Since around 2002, most of the monitored colonies on Bjørnøya and Spitsbergen have been stable or have increased slightly. The reason for the decline in some of the colonies in Svalbard is unknown, but it has been shown that rapid heating of the ocean has a negative influence on black-legged kittiwake. Since the colonies east of Svalbard have only been monitored since 2015, the overall trend for the Svalbard population is unclear.

In mainland Norway the species is declining rapidly, and black-legged kittiwakes are since 2015 classified as Endangered (mainland) and Near threatened (Svalbard) on the Norwegian Red List.

Causal factors

The reason for the decline in some Svalbard colonies of kittiwakes is not known.

Consequences

Considering that the overall status and trend of black-legged kittiwakes in Svalbard is unclear, the consequences for other parts of the ecosystems in Svalbard are also unclear.

About the monitoring

The black-legged kittiwake is the most numerous species of gull in the world and the most oceanic in its habits.

In Svalbard, the black-legged kittiwake is a common breeding species in all parts of the archipelago. The black-legged kittiwake is a surface-feeding bird (in contrast to other sea birds) that mainly feeds on invertebrates and small fish, but it also scavenges offal or discarded fish behind fishing boats. Chicks are fed regurgitated food. In Svalbard, capelin, polar cod, amphipods and euphausiids are common components of their diet. The total breeding population is estimated to be 270,000 pairs, of which ca 90,000 pairs breed on Bjørnøya.

Black-legged kittiwakes are monitored on Bjørnøya and in 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 such as the annual adult survival (Spitsbergen and Bjørnøya) and the average breeding success (Bjørnøya).

Places and areas

Fuglehuken is the next largest kittiwake colony in Svalbard, after Bjørnøya. Ossian Sarsfjellet is located in the innermost part of Kongsfjorden and is easily accessible from Ny-Ålesund.

Relations to other monitoring

Monitoring programme
International environmental agreements
Voluntary international cooperation
Related monitoring