NT
Wood Thrush Hylocichla mustelina



Justification

Justification of Red List Category
This species has been uplisted to Near Threatened on the basis of evidence that it has undergone a moderately rapid population decline over the past three generations.

Population justification
This species is characterised as common.

Trend justification

Survey data obtained in the species’s breeding range indicate that its population is in decline. Breeding Bird Survey (BBS) data yielded an average survey-wide yearly decline of 2.71% between 1999 and 2011, decreasing from an abundance index of 4.08 birds/route in 1999 to 2.86 birds/route in 2011 (Sauer et al. 2012). These results imply that the species underwent a c.30% decline over those 12 years (estimate of three generations). The trend between 1999 and 2011 appeared to be part of a longer term negative trend overall, stretching back to 1966 at least, when the annual index was 8.03 birds/route (Sauer et al. 2012). The average survey-wide yearly decline from 1966 to 2011 was 2.22%. Newer BBS data suggest a yearly decline of 1.11% between 2005 and 2015, which would equate to a decline of only c.13% over 3 generations (Sauer et al. 2017). Partners in Flight gave the species a 'half-life' of 31 years (Rosenberg et al. 2016), which would equate to a decline of 24% over 3 generations. Therefore, the decline is tentatively placed in the range of 20-29% over 3 generations.

Distribution and population

Hylocichla mustelina is a widespread breeding visitor to the eastern USA and south-eastern Canada, wintering in southern Mexico and Central America, south 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. It breeds from early May to late August, with pairs typically raising two broods. It is predominantly monogamous, with rare instances of polygyny. Pairs 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 primary threat to the species is likely to be the clearance and fragmentation of forests in both its breeding and non-breeding ranges, with pairs breeding in fragmented habitat potemtially suffering higher levels of nest predation and brood parasitism (del Hoyo et al. 2005, see also Etterson et al. 2014). Demographic models suggest that population declines are primarily driven by loss and fragmentation of non-breeding habitat in Central America (Taylor and Stutchbury 2016). Acid rain is also thought to impact breeding success by leaching calcium out of the soil, which is necessary for healthy egg production (del Hoyo et al. 2005).

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; using 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
Butchart, S., Westrip, J., Ekstrom, J., Symes, A., Taylor, J.

Contributors
Taylor, C., Cheskey, T.


Recommended citation
BirdLife International (2020) Species factsheet: Hylocichla mustelina. Downloaded from http://www.birdlife.org on 26/11/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 26/11/2020.