Short-term response of a declining woodland bird assemblage to the removal of a despotic competitor.

Galen Davitt,Martine Maron,Paul G Mcdonald,Kimberly Maute,Richard E Major

doi:10.1002/ece3.4016

Galen Davitt, Martine Maron + Show 3 more

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https://doi.org/10.1002/ece3.4016

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Abstract

Interspecific aggression by the noisy miner (Manorina melanocephala), a highly despotic species, is homogenizing woodland avifaunas across eastern Australia. Although a native species, the noisy miner's aggressive exclusion of small birds is a Key Threatening Process under national law. Large‐scale removal of noisy miners has been proposed as a management response to this threat following increases in miner presence due to anthropogenic land use practices. We tested this proposal by experimentally removing noisy miners from eucalypt woodland remnants (16–49 ha), assigned randomly as control (n = 12) or treatment (miner removal) sites (n = 12). Standardized bird surveys were conducted before and after removal, and generalized linear mixed models were used to investigate the effect of miner removal on bird assemblage metrics. Despite removing 3552 noisy miners in three sessions of systematic shooting, densities of noisy miners remained similarly high in treatment and control sites, even just 14 days after their removal. However, there was evidence of an increase in richness and abundance of small birds in treatment sites compared to controls—an effect we only expected to see if noisy miner densities were drastically reduced. We suggest that miner removal may have reduced the ability of the recolonizing miners to aggressively exclude small birds, even without substantially reducing miner densities, due to the breakdown of social structures that are central to the species' despotic behaviour. However, this effect on small birds is unlikely to persist in the long term. Synthesis and applications: Despite evidence from other studies that direct removal of noisy miners can result in rapid and sustained conservation benefit for bird communities at small scales, our findings cast doubt on the potential to scale‐up this management approach. The circumstances under which direct control of noisy miners can be achieved remain unresolved.

Highlights

A key mechanism through which landscape change drives shifts in faunal assemblages is the replacement of specialized and fragmentation-sensitive species by competitive commensal or invasive species
Despite removing 3,552 noisy miners (~10 birds/ha), there was no statistical support for a reduction in noisy miner abundance at treatment sites, indicating that the species could recolonize rapidly
Even though the treatment failed to reduce noisy miner density beyond a few days, surprisingly it led to at least a short-term increase in the abundance and species richness of small birds in particular. This effect was not as pronounced as would be expected if noisy miners were successfully extirpated, but the fact that it was evident despite no substantial reduction in the number of miners present is perplexing and may reflect how a perturbation to the noisy miner’s social structure alters the effectiveness of its interspecific aggression

Summary

| INTRODUCTION

A key mechanism through which landscape change drives shifts in faunal assemblages is the replacement of specialized and fragmentation-sensitive species by competitive commensal or invasive species. Species that have disproportionately large ecological effects are labeled “keystone” species, or more generally, “strong interactors” (MacArthur, 1972; Menge, Berlow, Blanchette, Navarrete, & Yamada, 1994) and they can be native or introduced These strong interactors may affect assemblages and ecosystems through a variety of ecological processes, including predation (Menge et al, 1994), habitat transformation (Naiman, Melillo, & Hobbie, 1986), and competition (Piper & Catterall, 2003). Interference competition from the noisy miner in particular is increasingly being recognized as one of the strongest drivers of avian assemblage composition in eastern Australia (Mac Nally & Horrocks, 2002; Maron et al, 2011; Piper & Catterall, 2003; Robertson, Maron, Buckley, & McAlpine, 2013) The species achieves this effect through its despotic habitat selection, whereby it excludes dozens of other bird species from areas of suitable habitat, prompting widespread. We present the initial results of this large-scale field experiment to contribute to the urgently needed body of information about management of this key threatening process

| MATERIALS AND METHODS

Findings

| DISCUSSION