Long-term changes in populations of rainforest birds in the Australia Wet Tropics bioregion: A climate-driven biodiversity emergency

ranges, tablelands, foothills and a lowland coastal plain. The elevation varies from sea level to highlands at 1000 meters, with isolated peaks reaching up to 1,620 meters with mid-elevation peaks (600-700m a.s.l.) in total rainforest area (Fig 4) [42]. Annual rainfall varies between 1200-8000mm with rainforest covering most areas with annual rainfall above ~1500mm. Data collection Rainforest birds in the Australian Wet Tropics bioregion were monitored between 1996 and 2016 across the region at locations ranging from 0 to 1500 meters above sea level. All individu- als were recorded either by call or visual observation. Each survey was based on a 30 minute- 150 meter transect with two observers. Surveys occurred within two hours of sunrise. All long- term monitoring sites were located within large, unfragmented areas of rainforest with contin- uous forest cover over the available elevational gradient and at least a kilometre from the forest edge. For further details of methods, species observed, site localities and species traits see Wil- liams, VanDerWal [52], Williams, Shoo [55]. Data from four mountain ranges were included in the analyses presented here (Atherton Uplands, Carbine Uplands, Spec Uplands and Windsor Uplands), representing a total of 1977 surveys across 124 different sites. Analysis across these sites was possible based on coverage of the elevational gradient and consistency and numbers of surveys over time. Years with an entire elevation category missing were not included in the trend analyses (from 1996 to 1999).

See supplementary material for complete breakdown of survey numbers by elevation and year. Species included Initially, all species for which the survey technique was unsuitable (e.g. water birds) or when call identification was considered unreliable due to the presence of multiple species with simi- lar calls were excluded to ensure maximum reliability in the trend analyses. This resulted in a dataset of 54 species. Of these, analysis of population trends across elevation and time was pos- sible for 42 species where there was sufficient data across both elevation and years to reliably analyse temporal changes in species abundance. We grouped species by habitat (rainforest spe- cialist, generalist) and elevation specialisation (lowland 0–450 m, midland 451-850m, upland Fig 4. Elevational profile of the Wet Tropics bioregion: (a) elevation map (m a.s.l. with UTM grid coordinates) and (b) rainforest area by elevational band. https://doi.org/10.1371/journal.pone.0254307.g004 PLOS ONE Rainforest birds on escalator to extinction PLOS ONE | https://doi.org/10.1371/journal.pone.0254307 December 22, 2021 10 / 16