LC
Northern Wren Troglodytes troglodytes



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 increasing, 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 extremely 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 32,700,000-56,500,000 pairs, which equates to 65,300,000-113,000,000 mature individuals (BirdLife International 2015). National population estimates include: c.10,000-100,000 breeding pairs in China; c.100-100,000 breeding pairs in Taiwan; possibly c.10,000-100,000 breeding pairs in Korea; c.100-100,000 breeding pairs in Japan and possibly c.10,000-100,000 breeding pairs and c.1,000-10,000 individuals on migration in Russia (Brazil 2009). It is likely that the global population is within the range 10,000,000-500,000,000 mature individuals.

Trend justification
In Europe the overall trend from 1980-2013 was increasing (EBCC 2015).

Ecology

This species inhabits a wide variety of habitats. In western Europe, it is most commonly found in deciduous and mixed woodland, well-vegetated suburbs, urban parks and gardens, moorland scrub, and offshore islands with very scanty cover. In North America it breeds primarily in boreal moist coniferous forest with extensive understorey, as well as on offshore islands with very stunted vegetation. In European Russia, egg-laying occurs from the second half of May; however in western Europe it begins late March or early April and a week or more later in central Europe. In Canada it breeds between May and July. The nest is a domed structure with a side entrance hole (Kroodsma et al. 2015) and is made of grass, leaves, moss and other vegetation, lined with feathers and hair (Snow and Perrins 1998). It is sited in a wide range of locations, often in dense vegetation but also in a cavity or crevice and will use artificial sites. Clutches can be three to nine eggs but most often five to eight. The diet is mostly invertebrates such as spiders (Araneae), beetles (Coleoptera), earwigs (Dermaptera) and orthopterans but it will also take small vertebrates, such as small fish, tadpoles and young frogs. The species is resident, migratory and partially migratory (Kroodsma et al. 2015).

Threats

Some island populations, which represent whole subspecies are very small and thus vulnerable; the designation of race hirtensis, on St Kilda (Scotland) in 1884 led to an increase in collecting activity, although there is no evidence this caused a significant decline. In non-migratory populations, severe winters with prolonged snow cover can decimate numbers but this is normally temporary and recovery is quick (Kroodsma et al. 2015).

Conservation actions

Conservation Actions Underway
Within Europe, the race fridariensis is listed on Annex I of the EU Birds Directive. Bern Convention Appendix II. There are currently no known conservation measures for this species within its European range.

Conservation Actions Proposed
No conservation measures are currently needed for this species within Europe.

Acknowledgements

Text account compilers
Ashpole, J, Butchart, S., Ekstrom, J., Khwaja, N. & Symes, A.


Recommended citation
BirdLife International (2017) Species factsheet: Troglodytes troglodytes. Downloaded from http://www.birdlife.org on 23/10/2017. Recommended citation for factsheets for more than one species: BirdLife International (2017) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 23/10/2017.