LC
Wood Thrush Hylocichla mustelina



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
The population is estimated to number 12,000,000 mature individuals (Partners in Flight 2019). It is described as common.

Trend justification
The species has been undergoing a large, significant decline in the past, with an average rate of 1.92% per year between 1970 and 2017 (Partners in Flight 2019, Evans et al. 2020). This amounts to an average decline of 18% over ten years. However, investigating short-term trends from the North American Breeding Bird Survey (BBS; Pardieck et al. 2018), it seems that declines have slowed down in recent years: For the decade 2001-2011, declines amounted to 28%; but since then the rate of decline has continuously been below 20%. For the period 2002-2012, the species declined by 19%, and rates of decline have decreased since. To calculate the rate of population change for the past ten years, we can assess the trend for 2010-2017 and extrapolate this to 2020, which results in a rate of decline of 11% over the past ten years.

Distribution and population

Hylocichla mustelina is a widespread breeding visitor to the eastern U.S.A. and south-eastern Canada, wintering in Central America from southern Mexico to Panama.

Ecology

This species breeds in the interior and edge of a variety of deciduous and mixed forest communities, preferring those with a moderate shrub/subcanopy layer and fairly open forest floor, shade, moist soil and decaying leaf litter (del Hoyo et al. 2005). On passage, the species frequents secondary growth and forest edge. In its non-breeding range, it occupies the interior understorey of humid to semi-humid broad-leaved evergreen and semi-deciduous forest and mixed palm forest, also occurring in secondary growth, low-stature forest, thickets and plantations. It feeds mainly on soil-dwelling invertebrates, and takes fruit from late summer to early spring (Jirinec et al. 2016, Evans et al. 2020). It breeds from early May to late August, with pairs typically raising two broods. It is predominantly monogamous, with rare instances of polygyny. Pair bonds usually last for a single season. It is a long-distance nocturnal migrant, leaving its breeding areas in mid-August to mid-September and crossing the Gulf of Mexico on a broad front from Texas to Florida, and making landfall from Veracruz, Mexico to Costa Rica (del Hoyo et al. 2005, Stanley et al. 2015). Individuals leave the non-breeding region during April (Stanley et al. 2012) and most birds (>70%) travel northwards through the central U.S. Gulf Coast (Stanley et al. 2015).

Threats

The species is threatened by the loss and fragmentation of its forest habitat both within the breeding and non-breeding ranges (Taylor and Stutchbury 2016, Evans et al. 2020). In fragmented habitats, breeding pairs suffer from lower reproductive success and higher prevalence of cowbird parasitism (Evans et al. 2020). Demographic models suggest that population declines are primarily driven by loss and fragmentation of non-breeding habitat in Central America (Taylor and Stutchbury 2016). Further threats include contamination by acid rain, disturbance at nest sites, pollution and window collisions (Evans et al. 2020).

Conservation actions

Conservation Actions Underway
This species has been the subject of targeted research and its population trends are captured through established survey programmes.

Conservation Actions Proposed
Continue to monitor population trends through established citizen science programmes. Investigate the possible causes of the decline. Carry out habitat restoration for the species. Increase the area of suitable habitat that receives formal and effective protection in both its breeding and non-breeding ranges; use modelling to aid in strategic conservation planning and predict possible future effects of certain activities (e.g. Bonnot et al. 2011, 2013, Beaudry et al. 2013).

Acknowledgements

Text account compilers
Hermes, C.

Contributors
Butchart, S., Ekstrom, J., Elliott, N., Symes, A., Taylor, J. & Westrip, J.R.S.


Recommended citation
BirdLife International (2021) Species factsheet: Hylocichla mustelina. Downloaded from http://www.birdlife.org on 28/10/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 28/10/2021.