LC
Garden Warbler Sylvia borin



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). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to 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
Shirihai et al. (2001) estimated the population to exceed 10 million individuals, but in Europe, the breeding population is estimated to number 16,700,000-26,900,000 pairs, which equates to 33,300,000-53,800,000 mature individuals (BirdLife International 2015). Europe forms c.80% of the global range, so a very preliminary estimate of the global population size is 41,625,000-67,250,000 mature individuals, placed here in the range of 41,000,000-67,999,999 mature individuals; although further validation of this estimate is needed.

Trend justification
In Europe, trends between 1980 and 2013 show that populations have undergone a moderate decline (EBCC 2015).

Ecology

During the breeding season it inhabits dense bushes, woodland fringes and riparian forest with abundant undergrowth. It favours shady zones with herbaceous vegetation and broadleaf scrub and also often bushes close to reedbeds. In the Alps it occurs in stands of green alder (Alnus viridis) and birch (Betula) and various willows (Salix). In central Europe it prefers the presence of hawthorn (Crataegus monogyna) and blackthorn (Prunus spinosa), and in Finland is associated with raspberry (Rubus idaeus). In Britain it is abundant in areas of sessile oak (Quercus petraea). In its African non-breeding range it uses woods, forest edge, orchards and gardens, sometimes entering forest when fruits are available. It also occupies savanna and dry zones with dense thicket vegetation, e.g. acacia (Acacia) and brachystegia (Brachystegia) woodlands. It avoids closed forest, but can enter open montane forest at up to 2,600 m, although it prefers lower altitudes. Breeding occurs from April to July. The nest is a cup constructed from plant material such as grass, leaves and roots and lined with fine grass and hairs. It is usually placed low down, hidden in tree or bush or among tall plants. Clutches are four or five eggs. The diet is  mostly insects throughout the year, especially during the breeding season, when some fruits and plant material are also taken. Through the rest of the year it is mostly frugivorous. The species is a long-distance migrant (Aymí and Gargallo 2015).

Threats

The spread of exotic Reynoutria spp. has been shown to reduce numbers of this species where it occurs (Hajzlerová and Reif 2014). Alterations or fragmentation of important refuelling habitats south of the Sahara could reduce survival (Aymí and Gargallo 2015).

Conservation actions

Conservation Actions Underway
CMS Appendix II. Bern Convention Appendix II. There are currently no known conservation measures for this species within Europe.

Conservation Actions Proposed
In areas where it is a problem, management actions should be developed that counter-act the invasion of Reynoutria spp. (Hajzlerová and Reif 2014).

Acknowledgements

Text account compilers
Ekstrom, J., Butchart, S., Ashpole, J

Contributors
Dowsett, R.J.


Recommended citation
BirdLife International (2021) Species factsheet: Sylvia borin. Downloaded from http://www.birdlife.org on 26/10/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 26/10/2021.