LC
Long-tailed Jaeger Stercorarius longicaudus



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
In Europe, the breeding population is estimated to number c.19,800-53,000 breeding pairs, equating to c.39,700-106,000 mature individuals (BirdLife International 2015). Europe forms approximately 15% of the global range, so a very preliminary estimate of the global population size is c.265,000-710,000 mature individuals, although further validation of this estimate is needed. The population is therefore placed in the band 250,000-749,999 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 size is estimated to be fluctuating (BirdLife International 2015).

Distribution and population

This species breeds in the high Arctic of Eurasia and North America, and has a circumpolar winter distribution in the Southern Oceans (del Hoyo et al. 1996).

Ecology

This species is marine and highly pelagic, rarely occurring within sight of land except when breeding. It feeds mainly on lemmings during the summer, but will also take shrews, many insects, berries and small birds when microtines are scarce. Its winter diet is largely unknown, but probably includes marine insects and fish, with some scavenging and kleptoparasitism. Breeding begins in June, with birds widely scattered over the Arctic and subarctic or montane tundra, up to 1,300 m in Scandinavia. The species is highly territorial (del Hoyo et al. 1996).

Threats

Long-tailed Jaegers face few threats as adult birds, but are susceptible to crashes in breeding success. Productivity is thought to fluctuate in accordance with changes in the population of lemmings, a key prey item during the breeding season (Furness et al. 2018). This species does however seem to have a large number of adults which do not breed in any particular year, which may result in a buffering of the populations's reproductive success in the face of adult numbers declining due to low food availability (Barraquand et al. 2014). Extended periods of lemming failure, however, are likely to begin to cause significant declines in the breeding population (Barraquand et al. 2014).

Conservation actions

Conservation Actions Underway
The following information refers to the species's European range only: The species has been the subject of a recent satellite tagging study, aimed at finding out more about its movements outside the breeding season (Gilg et al. 2013).

Conservation Actions Proposed
The following information refers to the species's European range only: Monitoring to more accurately determine the population of this species is needed. Further research into the ecological requirements and movements of this species would help inform future conservation measures.

Acknowledgements

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


Recommended citation
BirdLife International (2022) Species factsheet: Stercorarius longicaudus. Downloaded from http://www.birdlife.org on 05/12/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 05/12/2022.