NT
Blackpoll Warbler Setophaga striata



Justification

Justification of Red List Category
Even though the species is extremely abundant across its range, the species has been undergoing a significant decline since 1970. The rate of the decline is difficult to asses but assumed to be at least 25% over three generations (10.5 years). Therefore, the species is precautionarily listed as Near Threatened, but might warrant a further category change if new information on population trends becomes available.

Population justification
The population is estimated at around 59,000,000 mature individuals, equating roughly to 88,500,000 individuals in total (Rosenberg et al. 2016). The species is described as one of the most common birds in the breeding range in northern North America (Curson 2018). Density estimates vary between 1.5 pairs/10 ha in mountainous areas and  more than 40 pairs/10 ha in subalpine valleys in the northeastern part of the range (DeLuca et al. 2013). Usually, densities are higher in mature, deciduous forests than in conifer stands or younger plantations. There are no density estimates for the non-breeding range.

Trend justification
This species has been undergoing a statistically significant population crash since 1970 (Ralston et al. 2015). Partners in Flight estimates that while the 46 steeply declining North American landbirds may have lost a combined 1.5 billion individuals since 1970, nearly half of these individuals have been Blackpoll Warblers (Rosenberg et al. 2016). This equates to a reduction of 92% between 1970 and 2014. However, a significant data deficiency due to the remoteness of its breeding range makes the rate of decline is difficult to determine: Estimates range from 20.9% over three generations (10.5 years) (North American Breeding Bird Survey; Sauer et al. 2017) to 45.3% over three generations (Partners in Flight Landbird Conservation Plan; Rosenberg et al. 2016). It has to be noted that both estimates yield large confidence intervals due to data deficiency, indicating large uncertainties over the rate of decline.

Distribution and population

The species breeds in boreal forest throughout Canada and Alaska, ranging south into the extreme north-east of the U.S.A. (DeLuca et al. 2013, Curson 2018). It is a migratory species and overwinters in north-eastern South America, where it occupies a variety of habitats (DeLuca et al. 2013, Curson 2018).

Ecology

Throughout its breeding range, the species occupies boreal spruce and fir forests. Being a long-distance migrant, it leaves the breeding sites in northern North America in August and arrives to the wintering grounds in northern South America by September/October (DeLuca et al. 2013). There, it occurs east of the Andes (below 3,000 m) in a variety of habitats, including lowland forest, cloudforest, secondary growth, forest edges and plantations (Curson 2018). By April, the species migrates back to the breeding range, where it arrives mid-May/June (DeLuca et al. 2013). Insects are the predominant food source, supplemented with fruits during migration (Curson 2018).

Threats

Given its wide range of habitat use in the non-breeding range, forest loss and degradation there is not thought to be a key threat (DeLuca et al. 2013). The remote nature of its breeding range would also appear to make logging there unlikely to be a significant threat too (DeLuca et al. 2013). The species is frequently reported as suffering mortality by colliding with large structures during migration, but this in part could be a result of the species’s abundance, and so the impacts of this on its overall population dynamics may in fact be trivial (DeLuca et al. 2013).

The species’s breeding range is likely being affected by climate change. The area of the breeding range is predicted to expand by 2080 following a shift poleward (Ralston and Kirchman 2013). Yet, this shift potentially brings other species into competition with the Blackpoll Warbler, and turn lower-elevational areas into population sinks (DeLuca et al. 2013). In fact, modelling has suggested a three degree rise in average temperature could lead to the loss of nearly all high-elevation conifer habitat in the species’s breeding region (Rodenhouse et al. 2008).

Conservation actions

Conservation Actions Proposed
Monitor the population trend. Investigate the impacts of climate change on the distribution and assess potential range shifts. Investigate potential risks from coastal and offshore wind energy and increased oil and gas activities along the Atlantic coast during migration.

Identification

c.14 cm. Male in breeding plumage with black and white head, grey upperparts with black streaks, white underparts with black streaks; dark wings with two white wing bars; dark tail with white spots. Non-breeding male with greyish-olive upperparts with black streaks, white underparts; face with yellowish supercilium and dark eye-line; wings and tail as in breeding plumage. Female in breeding plumage is duller, with crown, nape and upperparts olive green-grey; underparts white-yellowish; wings with two white wing bars and tail with white spots. Non-breeding female similar to non-breeding male. Similar spp Breeding males similar to Black-and-white Warbler (Mniotilta varia), but distinguishable by its entirely black cap and white cheeks. In non-breeding plumage often confused with Bay-breasted Warbler (S. castanea) and Pine Warbler (S. pinus).

Acknowledgements

Text account compilers
Hermes, C., Ekstrom, J., Westrip, J., Butchart, S.


Recommended citation
BirdLife International (2022) Species factsheet: Setophaga striata. Downloaded from http://www.birdlife.org on 07/10/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 07/10/2022.