Justification of Red List category
Recent monitoring data indicate very rapid declines, especially at lower altitudes, of this species in response to climate change. These are expected to affect mid-elevations in the future as the so-called 'escalator to extinction' effect takes hold. For this reason, the species is assessed as Endangered.
The abundance of Fernwrens is calculated from the density and distribution of birds using data from standardised transect surveys along elevational gradients and the area of climatically suitable habitat at different altitudes in 2016 (Williams et al. 2021). The population is estimated at 450,000-1,000,000 mature individuals, with a best estimate of 660,000 mature individuals.
There appears to have been a substantial decline in population size in the last ten years, as predicted from climate change modelling (Williams et al. 2003). Annual monitoring undertaken 2000–2016 (1,970 plots, 62 different locations, 0–1,500 m altitude) revealed a highly significant decline of 57% in the total population over the ten years to 2016 from an estimated 1.54 million to 660,000 individuals. There were never many at low altitudes (<450 m), and the species appears to have disappeared at some lower sites (360–400 m) where it was present in the late 1990s (J. Grant unpublished, in Williams et al. 2021). Numbers increased at medium altitudes (450–850 m) until 2006 but declined after 2008-2012. At higher altitudes (>850 m), which has the smallest area, numbers rose until 2006 and stayed steady until monitoring stopped in 2016 (Williams & de la Fuente 2021). However, ongoing climate change is suspected to have the same impact on higher altitudes as it did at medium altitudes in the next three generations and so the rate of decline is broadly estimated to be the same.
Fernwrens are endemic to the Queensland Wet Tropics region, Australia, from Big Tableland in the north, south to Paluma and Bluewater Range near Townsville (Higgins and Peter 2002).
Fernwrens occur in upland rainforest, formerly attaining their highest densities at 1,200 m (Williams et al. 2021), feeding on insects extracted from the leaf litter (Frith 1984). They usually lay two eggs in a domed nest built near the ground (Higgins and Peter 2002).
Climate change is the only known threat and could be having both direct effects as a result of increased mortality during heat waves, which have been longer and hotter in the last two decades, and an indirect effect because the dry season has been longer, drier and hotter, which is likely to have reduced resource availability (Williams et al. 2021).
Conservation actions underway
Almost the entire range lies within protected areas.
Conservation actions proposed
Understand constraints on population size and survival. Identify reasons for sensitivity to climate change and options for countering them. Continue to monitor population size. Develop strategies for maintaining remaining populations. Apply adaptation strategies as required.
Text account compilers
Berryman, A., Vine, J.
BirdLife International (2023) Species factsheet: Oreoscopus gutturalis. Downloaded from http://datazone.birdlife.org/species/factsheet/fernwren-oreoscopus-gutturalis on 04/12/2023.
Recommended citation for factsheets for more than one species: BirdLife International (2023) IUCN Red List for birds. Downloaded from http://datazone.birdlife.org on 04/12/2023.