The conservation status of birds in arid Australia.

Abstract

The impression has been given in previous studies that there are few bird conservation problems in the arid zone, particularly because not one of a total of 230 species has become extinct. In stark contrast, almost half of the native terrestrial mammalian fauna of the Australian arid zone has become extinct on the mainland since European occupation. Here we show that the status of one half of the avifauna has changed since European occupation, and conclude there are many threats to avian biodiversity at the regional scale in the arid zone. There are 19 species (8%) in the arid zone classified as rare and threatened nationally. Twelve more (5%) are uncommon species which have declined or are at risk in two or more regions. A further 40 species (17%) have declined in at least one arid region, although many of these remain common and some have increased elsewhere in arid Australia. At least 45 species (20%) have increased in range or abundance, including a suite of ground-feeding birds associated with degraded landscapes. Striking patterns emerged from analysis of 29 threatened and declining species: • birds associated with chenopod shrublands and grassy, riparian or floodplain environments have been most affected whereas mulga inhabitants and canopy-dwellers of riparian woodland have been little affected; • birds generally with a northem distribution have declined in the south of the arid zone and birds with a southern distribution have declined in the north of the arid zone, and these patterns contrast with many birds with a southern or continental distribution which have declined more in southern semiarid regions than within the arid zone itself; • birds which feed at ground and low shrub height have been most adversely affected; • sedentary bushbirds (passerines) are more at risk than nomads and their limited mobility seems to be a risk factor; • among non-passerines, parrots, cockatoos and pigeons are most at risk, while three passerine families stand out, namely wrens, quail-thrushes, and thornbills and allies; • contrary to findings for mammals, size does not generally appear to be an important risk factor. Land degradation and habitat alteration such as shifts in abundance or dominance of plant species caused by the introduction of exotic herbivores appear to be the principal factors causing change in status while the provision of reliable water sources in pastoral districts is also important. Introduced predators are implicated in some cases and altered fire regimes may have played a part in spinifex and mallee habitats. Competitive interactions between increasing and declining species, although not demonstrated, appear to be likely for some species. We have documented a hitherto unsuspected degree of change in avian biodiversity in the Australian arid zone. In the absence of widespread regeneration of dominant plant species in the southern arid zone, the decline of many arid zone birds will accelerate dramatically. Also, unless better management ensues, the next major drought could cause accelerated declines and extinctions. We advocate a range of measures designed to improve the conservation prospects for arid Australian birds, including lower stocking rates on pastoral properties, rehabilitation of critical habitats and their protection from exotic herbivores, experimental research on the impact of grazing and predation, and monitoring of both threatened species and a range of sedentary passerines typically associated with representative habitats in the arid zone.

Low-density koala (Phascolarctos cinereus) populations in the mulgalands of south-west Queensland. IV. Abundance and conservation status

“…There is substantial evidence that the recruitment of many long-lived perennial tree species by seed or vegetative suckers is inhibited under grazing pressure (Lange and Graham 1983;Auld 1995). It has long been suggested that in Australia the major cause of reduced regeneration of perennial trees and grasses were rabbits, goats (Lange and Graham 1983) and domestic stock (Auld 1995), particularly in riverine communities (Reid and Fleming 1992). However, anecdotal evidence collected throughout this study suggests that Eucalyptus species in riverine communities regenerate well in comparison to some residual communities.…”

Conserving migratory and nomadic species

“…Nomads instead can be highly habitat specific, keying into specific environmental conditions such as vegetation seeding and flowering events (Ziembicki & Woinarski 2007;Pavey & Nano 2013;Tischler et al 2013;Webb et al 2014), making them less resilient to environmental change than generalist sedentary species. There has been widespread modification and transformation of vegetation across inland Australia, with 46% of the continent subject to grazing of native vegetation (SoE 2011), and this is likely to have impacted nomadic birds (Reid & Fleming 1992).…”

“…Movement itself could be risky in the sense that locations and timings of suitable resources are unpredictable and irregular (MacNally 2009). Additionally, in some cases, threats can be concentrated into precisely the areas to which nomadic species contract ; for example, both invasive predators and livestock grazing follow rainfall patterns during prolonged drought (Reid & Fleming 1992;Grenville et al 2014). …”

“…Resource fluctuations comprise annual seasonality overlain onto longer and less predictable "boom and bust" cycles in resources (Meyers et al 2007;Risbey et al 2009). Nomadic species in Australia face a suite of threats including habitat loss through degradation and human encroachment, climate change and pressure from introduced species (Reid & Fleming 1992;Cleugh et al 2011;Ford 2011;Garnett et al 2011). …”

“…Failing to protect critical sites, including bottlenecks, may result in irreparable population declines or extinction (Reid & Fleming 1992;Woinarski et al 1992). …”