Justification of Red List Category
Recent monitoring data indicate rapid declines of this species in response to climate change. For this reason, it is assessed as Vulnerable.
The abundance of Mountain Thornbills 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. 2010a, 2021); the population thus numbers 380,000-1,770,000 mature individuals, with a best estimate of 820,000.
There appears to have been a substantial decline in population size in the last three generations, as predicted by climate change modelling (Williams et al. 2003). Annual monitoring undertaken between 2000–2016 (1,970 plots, 62 different locations, at 0–1,500 m altitude) revealed a highly significant 46.3% decline in the total population over the 10 years to 2016 from an estimated 1.53 million to 820,000 individuals (Williams & de la Fuente 2021). Numbers increased from 2000–2008 at both mid-altitudes (450–850 m) and higher altitudes (>850 m) before commencing a rapid decline, again as expected from models. This so-called 'escalator to extinction' effect is predicted to cause an ongoing rate of decline of 40-49% every ten years.
Mountain Thornbills are endemic to the Queensland Wet Tropics region, Australia, from Shiptons Flat, near Cooktown, south to Paluma Range and inland to near Herberton and the Mt Windsor Tableland (Higgins and Peter 2002).
Mountain Thornbills occur in upland rainforest, attaining their highest densities at about 1200 m (Williams et al. 2010b), feeding on insects gleaned from foliage within the canopy (Keast 1978). They probably lay 2–3 eggs in a domed nest built in the outer canopy of low trees (Higgins and Peter 2002). However, Freeman et al. (2015) found Mountain Thornbills to be more abundant in ecological restoration sites than in primary rainforest.
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. 2010b, Williams and de la Fuente 2021).
Conservation Actions Underway
Almost the entire species's range is 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. Develop strategies for maintaining remaining populations. Apply adaptation strategies as required.
Text account compilers
Berryman, A., Vine, J.
Butchart, S., Ekstrom, J., Fisher, S. & Harding, M.
BirdLife International (2022) Species factsheet: Acanthiza katherina. Downloaded from http://www.birdlife.org on 29/11/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 29/11/2022.