Tree hollow densities reduced by frequent late dry-season wildfires in threatened Gouldian finch (

S L J Oliveira,B Byrne,L.-A Woolley,I J Radford

doi:10.1071/wr20108

Abstract

Abstract Context. Tree hollows are a key habitat resource for hollow-nesting species, including the northern Australian Gouldian finch (Erythrura gouldiae). Certain fire and disturbance regimes limit tree hollow availability in the northern Australian savannas. Aims. This study investigated the influence of fire regime and vegetation structure on the density of tree hollows at Gouldian finch breeding sites. Methods. Fire scars were mapped across breeding sites by using LANDSAT images. Vegetation plots within sites were spatially stratified according to three fire-regime attributes, namely, fire frequency, late dry-season wildfire frequency and time since the last fire. Tree hollow and vegetation structural attributes were measured at each vegetation plot. We modelled the relationship among hollow density, fire and vegetation attributes by using general linear mixed models with site as the random factor. Key results. We found that the highest tree-hollow density was found at plots with high eucalypt tree density and cover and with the lowest frequency of late dry-season wildfires (<1 wildfire over 5 years). Tree-hollow density declined after >2 years without fire. Hollow density was not directly related to total fire frequency. Conclusions. This study adds to previous work on grass seed resources in highlighting the importance of fire in Gouldian finch ecology. This study particularly highlighted the importance of reducing the impacts of high-intensity late dry-season wildfires because of their negative impacts on tree-hollow density, which is a key resource for breeding Gouldian finches. Implications. We recommend the use of a network of interconnected annual patchy early dry-season prescribed burns for protecting Gouldian breeding habitat from threat of high-intensity wildfires. We do NOT recommend fire exclusion from Gouldian finch breeding habitats. This is because fire risks to hollow-bearing trees, and grass seed resources, increase with the long-term accumulation of savanna litter fuels in the absence of fire.

Highlights

North Australian savanna ecosystems are currently undergoing a biodiversity crisis thought to be at least in part attributable to inappropriate fire regimes (Franklin 1999; Franklin et al 2005; McKenzie et al 2007; Woinarski et al 2011; Woinarski and Legge 2013)
This study adds to previous work on grass seed resources in highlighting the importance of fire in Gouldian finch ecology
This study highlighted the importance of reducing the impacts of high-intensity late dry-season wildfires because of their negative impacts on tree-hollow density, which is a key resource for breeding Gouldian finches

Summary

Introduction

North Australian savanna ecosystems are currently undergoing a biodiversity crisis thought to be at least in part attributable to inappropriate fire regimes (Franklin 1999; Franklin et al 2005; McKenzie et al 2007; Woinarski et al 2011; Woinarski and Legge 2013). Fire regimes in much of northern Australia, since the loss of traditional indigenous fire management, have been dominated by high-intensity, frequent, extensive wildfires occurring in the late dry season (Russell-Smith et al 2003a). Much of the savanna biota is thought to be fire resilient (Williams et al 1999; Russell-Smith et al 2003b; Clarke et al 2015; Andersen 2020), most threatened elements of the savanna biota appear to be vulnerable to large fires, frequent fires or to high-intensity late dry-season wildfires (Andersen et al 2005; Legge et al 2008, 2015; Lawes et al 2015; Radford et al 2015, 2020; Corey et al 2020). Few savanna taxa respond favourably to the long-term absence of fire because this leads to progressive conversion of savanna to closed forest with forest-dominated biota (Woinarski et al 2004; Andersen et al 2014)

Methods

Results

Discussion

Conclusion