ACT LOWLAND WOODLAND CONSERVATION STRATEGY 4 Lowland Woodland Fauna 4.1 woodland plants and are involved in nutrient recycling and maintenance of soil condition. Loss of species can Introduction alter ecosystem processes, which may adversely affect the health of the ecosystem. Some of the factors The crescent of temperate eucalypt woodland that now contributing to the decline of ecosystem health in stretched from southern Queensland to South Australia temperate eucalypt woodlands have been outlined in provided animals with a diversity of habitats. Woodland Chapter 2. The well-known phenomenon of rural tree fauna includes birds, bats, reptiles, amphibians, dieback is a notable example of an altered ecosystem ground dwelling and arboreal mammals, and process that has resulted in widespread impact at the invertebrates. The hollows developed in older tree landscape level. One of the possible explanations for trunks and branches, together with fallen wood, the increasing occurrence and severity of insect- provide essential shelter for many of these species. mediated dieback is a reduction in the abundance and Loose bark provides shelter for some of the efficacy of natural controls of damaging insects, in invertebrates that provide food and nesting material particular the decline in insectivorous birds and insect (e.g. spider web) for birds. Healthy, mature woodland parasitizers of pasture scarabs (Reid and Landsberg trees are an important source of nectar and their open 2000; Martin and Green 2002). The health of woodlands canopies allow the development of a species-rich is in large measure dependent on retention of woodland understorey of tussock grasses and forbs, which is fauna assemblages. habitat for a range of fauna and is grazed by the larger marsupials. Many fauna species found in woodlands It is beyond the scope of this Strategy to provide detailed also occur in other habitats such as forests, riparian information for all woodland animal species. In discussing zones or grasslands. Some species, however, are woodland fauna and its conservation, this Strategy places restricted almost entirely to woodland habitats. an emphasis on woodland birds. The reasons for this are: ■ Birds are valuable indicators of habitat modification More recent additions to woodland fauna include the and ecosystem health. This is because they occupy Dingo, which was brought to Australia by humans a diversity of niches, often at the apex of the food around 3500–4000 years ago (Corbett 1995), and chain, and their species composition and abundance several domestic and feral species that were may reflect the underlying state of the ecosystem. introduced either deliberately or inadvertently following ■ Actions aimed at conservation of woodland bird European settlement. Domestic species include cattle, species and habitat will also benefit other sheep and horses, whereas feral animals include pigs, woodland fauna. rabbits, hares, cats, foxes, dogs, mice, Starlings and ■ Birds are highly visible and the strong community Common Mynahs. interest and skill in observing birds means more information is generally available on species 4.2 composition and abundance than for other types of animals. Fauna as Part of the Woodland ■ The effects on birds of habitat loss and modification Ecosystem are relatively well studied compared to other faunal Woodland animals are an intrinsic part of the overall groups. functioning of woodland ecosystems. They are ■ The eight threatened woodland animal species in the essential for pollination and dispersal of many ACT are all birds (see Table 4.1), and this Strategy incorporates the Action Plans for these species. 37 ACT LOWLAND WOODLAND CONSERVATION STRATEGY 4.3 larger area in poor quality or degraded habitat. Animal populations too small to be viable in the long term may Threats to Fauna persist for some time in remnants following habitat fragmentation, resulting in a time lag (in some cases Widespread clearing, habitat modification and years or decades) between habitat disturbance and fragmentation of woodlands since European species decline (Recher and Lim 1990; Saunders et settlement (see Chapter 2) have had a severe impact al. 1991; Traill 2000). Such time lags can occur if on the habitat of woodland animals. Other threats individuals are long-lived (but may not be breeding) or include increased predation by introduced predators if the habitat is sufficient to satisfy the requirements of and human disturbance. These threats to woodland the species during good conditions, but not during or fauna are described in more detail in the following following major environmental disturbances such as sections. drought or fire. 4.3.1 Continued Removal and The degree of isolation or connectivity of a remnant Fragmentation of Habitat determines its potential for recolonisation and is a critical issue for fauna conservation. Connectivity has Clearance of native vegetation still remains the most been defined as ‘the degree to which the landscape significant threat to terrestrial biodiversity despite facilitates or impedes movements among patches’ apparently tight legislative controls (Australian State of (Bennett 1999). Distance from other remnants is the Environment Committee 2001) and is listed as a important for less mobile species (e.g. reptiles and key threatening process in NSW and nationally. amphibians) or species reluctant to cross large open Expanding urban development increases pressure on areas (e.g. the Brown Treecreeper (Climacteris remnants of native vegetation, while construction of picumnus), Squirrel Glider (Petaurus norfolcensis), roads and other urban infrastructure leads to Sugar Glider (Petaurus breviceps) and Common increased fragmentation of habitat. There is an Ringtail Possum (Pseudocheirus peregrinus)). Lack of extensive literature on the effects of fragmentation on connectivity in highly fragmented woodlands is clearly fauna, especially birds and mammals (Andren 1994). a threat to the long-term viability of animal populations The effects of habitat removal and fragmentation have (Smith and Hellmann 2002), though the best means of been particularly noticeable for birds, a relatively well rebuilding connectivity is subject to debate and studied woodland fauna group (e.g. Robinson and depends upon the species in question. Traill 1996; Freudenberger 1999; Reid 1999; Garnett and Crowley 2000; NLWRA 2002). Land clearance has The value of corridors has been debated on the basis affected over 82 percent of all bird taxa from mainland of adequate width, high cost and edge effects. An Australia and Tasmania, with almost half of the alternative is closely spaced patches forming ‘stepping affected taxa occurring in temperate or subtropical stones’ (Beier and Noss 1998; Martin and Green 2002; woodlands (Garnett and Crowley 2000). More than Freudenberger 2001). Stepping stones are likely to 25% of the landbirds of woodlands are either benefit species that are sufficiently mobile to cross threatened or in apparent decline (Robinson and Traill areas of unsuitable habitat (such as some birds) but 1996, Reid 1999). It has been estimated that may not benefit less mobile species such as many 1000–2000 birds permanently lose their habitat for reptiles and small ground-dwelling mammals such as every 100 ha of woodland that is cleared (Australian Antechinus. Even amongst highly mobile species, State of the Environment Committee 2001). fragmentation can result in the necessity to move greater distances between resources, such as The size of remnants is critical for many animal between feeding and breeding habitats. This has species. The Brown Treecreeper and Hooded Robin apparently occurred for the Superb Parrot (Polytelis have declined or disappeared from fragments of less swainsonii), which is also reluctant to cross large than 300 ha (Freudenberger 1999; Garnett and areas of open ground in local foraging movements Crowley 2000) and many more species are absent (Higgins 1999). Movement between fragments can from remnants below 20 ha (Traill 2000). Larger also increase exposure to risks such as predation or terrestrial predators such as the Lace Monitors may road collision (e.g. ground-feeding parrots, kangaroos require home ranges of 500 ha or more. Minimum in the Canberra urban area, and migrating Eastern patch size for bats and arboreal and ground dwelling Snake-necked Turtles (Chelodina longicollis)). mammals to persist in the short term is likely to be approximately 10 ha in good quality habitat and a 38 ACT LOWLAND WOODLAND CONSERVATION STRATEGY 4.3.2 Degradation of Existing Habitat Fallen timber, leaf litter and other ground cover provides important habitat for a range of invertebrates, The major threat to animals in existing habitat, even many of which depend on dead wood and leaves for where the habitat may have sufficient area and their survival. These invertebrates, together with connectivity, is the degradation of that habitat and microbial organisms and fungi, are important in the especially loss of habitat diversity. Ecosystems with a breakdown of timber (Araya 1993) and recycling of complex ‘architecture’ support more species than nutrients back into the soil. In turn, invertebrates ecosystems that have been simplified, and many provide the main food source for a range of woodland species require a complex vegetation structure to meet birds, reptiles, amphibians and some mammals. their habitat requirements (Mac Nally 1995). Structural Indeed, many reptiles, small mammals, and birds complexity is created by the