Lower reporting rates after two decades for most bird species at a Wet Tropics Field Station

Abstract

Across Australia’s Wet Tropics region, populations of rainforest-dependent birds have declined because of climate change. Reforestation and regenerating secondary forest on abandoned agricultural land may help bolster species’ populations by expanding and connecting habitat. However, little is known about the value of these habitats for rainforest birds, or the impacts of climate change on secondary forests and their fauna compared with primary forests. At a 62-ha, mid-elevation property with primarily secondary forest cover on the Atherton Tablelands, in the Wet Tropics region, Queensland, we examined changes in bird species reporting rates on weekly lists between 2000–2005 and 2014–2019. Reporting rates of grassland and eucalypt-forest species decreased as expected because the area of ungrazed pasture was reduced over time, while the area occupied by tree plantings and naturally regenerating forest increased and matured. Reporting rates of most mixed-forest (61%) and nearly half (47%) of rainforest-dependent bird species also decreased significantly between the two time periods, despite the quality of rainforest habitat improving at the site. We infer that climate change is the cause of these declines. Five of the rainforest-dependent bird species whose reporting rates decreased in this study are known to have moderately increased in abundance in mid-elevation primary forest. Hotter, drier secondary forests may not be as well buffered as primary forest from the impacts of climate change, reducing their suitability as habitat for many bird species such as these. However, further studies are needed in secondary forests to investigate this.