LC
Arctic Jaeger Stercorarius parasiticus



Justification

Justification of Red List Category
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be stable, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

Population justification
The European population is estimated at 39,900-56,200 pairs, which equates to 79,800-112,000 mature individuals (BirdLife International 2015). Europe forms approximately 20% of the global range, so a very preliminary estimate of the global population size is c.400,000-560,000 mature individuals, although further validation of this estimate is needed. National population sizes have been estimated at c.50-10,000 wintering individuals in Japan and c.100-100,000 breeding pairs and c.50-10,000 individuals on migration in Russia (Brazil 2009). The population is therefore placed in the band 400,000-599,999 mature individuals.

Trend justification
The population is suspected to be stable in the absence of evidence for any declines or substantial threats. The European population trend is unknown (BirdLife International 2015).

Distribution and population

This species breeds on the northernmost coasts of Eurasia and North America. It is a transequatorial migrant, wintering on the southern tips of South America (as far north as Peru and Argentina), Africa (as far north as South Africa and Angola), and on the coasts of Australia and New Zealand, excluding the northern half of Australia (del Hoyo et al. 1996).

Ecology

This marine species is predominately coastal, but will migrate over land. Most or all of its food is obtained by kleptoparasitism when nesting near other seabird colonies. Otherwise, its diet can include microtine rodents, adult and fledgling passerines, wader chicks, birds eggs, insects and berries. Breeding begins in May or June, occurring later in the north then the south. It is either colonial at seabird sites or widely scattered across the tundra, where it is territorial (del Hoyo et al. 1996).

Threats

Arctic Jaegers have been classified as highly sensitive to changes in sandeel populations (ICES 2017), with decreases in sandeel stocks causing declines in the northernmost Scottish populations. Localised persecution of this species occurs on Iceland, the Faroes, Northern Scotland and across Scandinavia (Furness et al. 2018), in order to alleviate stresses to other seabirds and due to the species's aggressive behaviour towards humans during the breeding season. However, the level of persecution remains low and has declined in more recent years owing to the increased legal protection for this species.

Conservation actions

Conservation Actions Underway
The following information refers to the species's European range only: There are currently no known significant conservation measures for this species.

Conservation Actions Proposed
The following information refers to the species's European range only: As the populations in Russia are poorly monitored and population estimates are very approximate (Furness 1996), better monitoring is required.

Acknowledgements

Text account compilers
Ashpole, J, Butchart, S., Calvert, R., Bennett, S., Ekstrom, J., Martin, R., Stuart, A.


Recommended citation
BirdLife International (2020) Species factsheet: Stercorarius parasiticus. Downloaded from http://www.birdlife.org on 23/10/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 23/10/2020.