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Birds of a feather flock together: Using trait-groups to understand the effect of macropod grazing on birds in grassy habitats
... Therefore, management that burns or cuts tussocks will reduce perch availability and thus perching birds. On the other hand, coincident with Howland et al. (2016) for birds in Australian temperate grasslands, large species responded negatively to increasing grass height. In contrast, Soderstrom et al. (2001), working in seminatural dry pastures of farmland landscapes in Sweden found that larger insectivorous bird species tended to prefer intermediate levels of grass height. ...
... Regarding foraging behavior, we found that species that forage in the lower stratum of the grassland preferred short grass and low tree cover. Coincident with this finding, ground insectivores/omnivores birds tend to be more abundant in savannas ecosystems with short grasses (Howland et al., 2016;Neilly & Schwarzkopf, 2019;Soderstrom et al., 2001). Birds that feed on the ground can find food more easily (e.g., arthropods and seeds) when the grass is short and does not represent visual obstruction (Butler & Gillings, 2004). ...
... Birds that feed on the ground can find food more easily (e.g., arthropods and seeds) when the grass is short and does not represent visual obstruction (Butler & Gillings, 2004). The positive response of ground-feeding species to short grass has been observed in other species such as grassland shorebirds (Aldabe et al., 2019) and in other grassy regions such as Australia and Sweden (Howland et al., 2016;Neilly & Schwarzkopf, 2019;Soderstrom et al., 2001). Our results support the hypothesis that bird foraging strata preferences are a good predictor of species susceptibility to grazing (Martin & Possingham, 2005), as short grass is an indicator of high grazing intensity (Da Trindade et al., 2016). ...
Areas used for livestock production and dominated by native grasses represent a unique opportunity to reconcile biodiversity conservation and livestock production. However, limited knowledge of individual species’ responses to rangeland management restricts our capacity to design grazing practices that favor endangered species and other priority birds. In this work, we applied Hierarchical Modelling of Species Communities (HMSC) to study individual species responses, as well as the influence of traits on such responses, to variables related to rangeland management using birds of the Rio de la Plata Grasslands as a case study. Based on presence–absence data collected in 454 paddocks across 46 ranches we inferred the response of 69 species considering imperfect detection. This degree of detail fills a major gap in rangeland management, as species‐level responses can be used to achieve targeted conservation goals other than maximizing richness or abundance. We found that artificial pastures had an overall negative impact on many bird species, whereas the presence of tussocks had a positive effect, including all threatened species. Grassland specialists were in general sensitive to grass height and tended to respond positively to tussocks but negatively to tree cover. Controlling grass height via adjustments in stocking rate can be a useful tool to favor grassland specialists. To favor a wide range of bird species in ranches, a mosaic of short and tall native grasslands with patches of tussocks and trees is desirable. We also found that species‐specific responses were modulated by their traits: small‐sized birds responded positively to tussocks and tree cover while large species responded negatively to increasing grass height. Ground foragers preferred short grass while birds that scarcely use this stratum were not affected by grass height. Results on the influence of traits on bird responses are an important novelty in relation to previous work in rangelands and potentially increase our predicting capacity and model transferability across grassland regions.
... In the case of grazed grasslands, very few studies have evaluated which bird traits are associated with this habitat (e.g. Howland et al. 2016;Vaccaro et al. 2019), despite other studies that have emphasized the relevance of cattle pastures, as opposed to other anthropogenic habitat types, for the conservation of natural grasslands (Vaccaro et al. 2019). Furthermore, comparisons between studies cannot be direct because the traits found depend on the similarity of the habitats being compared. ...
... Furthermore, comparisons between studies cannot be direct because the traits found depend on the similarity of the habitats being compared. Some other studies, however, have evaluated which bird traits are associated with grazing by comparing grazed and non-grazed sites (Howland et al. 2016;Francis et al. 2020). In our study, bird species associated with grazed grasslands were species of open habitats such as waterbirds and non-wetland-dependent species such as Guira guira, Tyrannus melancholicus and Columbina picui. ...
... Thus, the presence of trees in grazed grasslands constitutes an indispensable resource for some species. Construction of ground nests also was associated with grazed grasslands, an association also found by Vaccaro et al. (2019), although opposed to the one reported by Howland et al. (2016). In our study, association of ground nesting with grassed grasslands reflected the significant proportion of species that were positively associated with grazed grasslands and that nest on the ground (9/27 species). ...
Floodplain wetlands are frequently used for cattle grazing so understanding the impact of this activity is crucial for biodiversity conservation and management. Cattle grazing can lead to the replacement of tall natural grasslands with shorter, grazed ones, a structurally different habitat. Understanding the effects of this change on birds in floodplain wetlands is necessary for effective conservation efforts. Here, we assessed the relationship between presence-absence of grazed grasslands in the floodplain landscape and i) number of habitats per site, ii) taxonomic and functional bird diversities, iii) frequency and abundance of bird species, and iv) bird functional traits, using data from extensive bird sampling (via point counts) in the Paraná River floodplain. We found scale-dependent results. At point-count scale, presence of grazed grasslands led to an increase in number of habitats, bird species richness, and functional diversity per site. When we compared bird diversity indices based on the combination of all point counts using rarefaction curves, only functional diversity was higher in counts with grazed grasslands. One species (Geothlypis velata) was associated with the absence of grazed grasslands while 27 species (17%) were related to their presence. Thirteen bird traits (48%), including non-wetland dependency, were positively associated with grazed grasslands. Our results show that grazed grasslands increase bird diversities because a set of species, mainly birds typical of agricultural uplands, are associated with this cattle-created habitat. Further, birds associated with grazed grasslands modified the functional structure of assemblages, adding even exclusive traits such as brood parasitism that can pose a threat to floodplain birds.
... Grazing pressure in the ACT reser ves Heavy grazing pressure, associated with high-density kangaroo populations, can cause loss of herbaceous biomass (McIntyre et al. 2010), and local loss of threatened plant and animal species (Coulson 2001(Coulson , 2006Howland et al. 2014Howland et al. , 2016a. Specifically, selective grazing by kangaroos in the ACT has been demonstrated to modify the habitats of grassland plants, birds, reptiles and invertebrates (Barton et al. 2011;Howland et al. 2014Howland et al. , 2016bMcIntyre et al. 2018). ...
... To address these issues, the preferred approach identified in the Kangaroo Management Research Workshop towards managing the grassy layer was to determine a 'safe operating environment' (adapted from Rockstr€ om et al., 2009) for key characteristics known to influence biodiversity responses, such as grass height, percentage of bare ground and thatch depth (Howland et al. 2014(Howland et al. , 2016aSmith et al. 2018;Snape et al. 2018). The Workshop also identified that detailed mapping of key grass communities within reserves, coupled with annual monitoring of grassy layer structure, and modelling of anticipated pasture growth rates at the management polygon scale, would provide an improved basis for managing the impacts of kangaroo grazing as part of an integrated approach to protecting conservation values. ...
... Local research suggests that the greatest biodiversity benefits occur at an average grass height of between approximately 5 and 12 cm (Howland et al. 2014(Howland et al. , 2016aSmith et al. 2018;Snape et al. 2018) although specific 'safe operating environments' are likely to vary amongst grassy communities and/or reserves depending on individual priority biodiversity values. A heterogeneous grass layer (e.g. ...
Populations of macropods are higher than estimated pre-European densities in many parts of Australia. To achieve appropriate densities of macropods in the Australian Capital Territory's nature reserves, multi-tenure kangaroo management units are used to tailor management of kangaroos and total grazing pressure to achieve conservation objectives. An adaptive management framework is recommended that monitors the state of the ground-layer vegetation and alters the cull accordingly. This case study may provide insights for kangaroo management in other temperate areas of Australia.
... At natural densities, herbivorous mammals play a key role in the structure and functioning of ecosystems (Côt e et al., 2004;Danell et al., 2006;Foster et al., 2014). However, high-intensity grazing can also have pervasive impacts on native ecosystems through changes in primary production (Frank and McNaughton, 1993), fire regimes (Hobbs, 1996), nutrient cycling (Molvar et al., 1993), soil properties (Abdel-Magid et al., 1987), vegetation structure (Eldridge et al., 2017b;Travers et al., 2019) and species distribution (Bird et al., 2012;Foster et al., 2014;Howland et al., 2014;Howland et al., 2016b;Mutze et al., 2016b, a). ...
... Macropod densities have also increased across southern Australia more broadly (DEE, 2018). Further, recent field studies have demonstrated the impacts of kangaroo grazing on native vegetation (McIntyre et al., 2010) and associated fauna (Howland et al., 2016b). In addition, there is some evidence of an increase in the density of exotic rabbits at some South Australian localities over a similar time period (Mutze et al. 2015(Mutze et al. , 2016aBarnett et al., 2018). ...
Protected areas are critical for the long-term conservation of biodiversity globally. Across agricultural landscapes, protected areas serve as refuges for threatened and declining species and provide valuable ecosystem services that support broader landscape function. However, increasing pressure on protected areas from a range of sources is undermining their unique conservation values. Much of the native vegetation remaining in southern Australia is now protected from broad-scale clearing, but the management of threats within these areas could be inadequate to maintain their biodiversity. In particular, grazing by domestic and wild mammalian herbivores can have a significant impact on the condition of remnant native vegetation, even if it is formally protected. We evaluated the evidence for grazing-pressure trends in native vegetation in both protected and unprotected areas across an agricultural landscape covering c. 180 000 km² of South Australia. Using total grazing pressure data from 1298 sites surveyed between 2004 and 2016, we employed Bayesian linear mixed-effects modelling to demonstrate increasing trends in grazing severity in four of five study regions, estimating that 45%–54% of grazed plants were heavily or severely grazed by 2016. Over the 12-year period, grazing severity in protected areas increased to levels closely matching those on private, unprotected land. Our results suggest that abundant native and/or introduced grazing animals are having an increasing impact on native vegetation across large areas of the agricultural zone of South Australia, with a disproportionate impact on protected areas. We recommend that: (1) research is needed to identify sustainable total-grazing-pressure thresholds; and (2) options should be considered for an adaptive, coordinated, and cross-tenure approach to maintaining total grazing pressure in protected areas below these thresholds.
... Yet, it can also result in the creation of additional habitat for some others. For example, some species of large macropods (e.g., the Eastern Grey Kangaroo [Macropus giganteus]) have benefited from the establishment of pastures and derived grasslands as a result of clearing of forests and woodlands (Howland et al. 2016). In other cases, fragmentation of habitat can have benefits for species persistence. ...
Australasia is home to many iconic species of marsupials, most found nowhere else. The region also leads the world in marsupial declines and extinctions. There are many causes of marsupial decline with focus in this chapter on habitat loss and habitat fragmentation. While habitat loss and habitat fragmentation are typically considered together, they are actually separate processes. However, many landscapes are subject to the simultaneous, co-occurring effects of both habitat loss and habitat fragmentation. In this chapter, some of the key human-generated factors contributing to habitat loss and habitat fragmentation for Australasian marsupials are outlined. This is done by providing a brief précis of the impacts of such drivers as land clearing, forestry, fire, and the establishment of human infrastructure. The authors also discuss how these drivers often interact – which is a major problem as the number of threats to which a species is exposed is a key driver of eroded resilience to decline in populations of vertebrates globally. It is highlighted why understanding the drivers of marsupial decline is important, especially as it informs how conservation efforts can be targeted to limit declines. This chapter is concluded with commentary on what is needed to mitigate the effects of habitat loss and habitat fragmentation on marsupials. These include better legislation, greater funding to tackle drivers of species decline, and more long-term monitoring to quantify temporal trends in marsupial populations (including the effectiveness of management interventions to recover species).
... On-ground vegetation surveys, ideally incorporating measures of composition and structure need to be incorporated into the possum monitoring. Although not the focus of this study, we acknowledge the growing evidence of the need for effective kangaroo population reduction to prevent overgrazing, particularly in areas where kangaroo populations are not regulated by a predator (Barton et al. 2011;Manning et al. 2013;Howland et al. 2014Howland et al. , 2016Rees et al. 2017;Mills et al. 2020;Neilly and Cale 2020;Finlayson et al. 2021;Fisher et al. 2021). To deliver effective management interventions we need to understand the drivers of decline. ...
Australia’s terrestrial mammalian fauna have experienced severe declines since European settlement. On the Murray–Darling floodplain in south-eastern Australia, common brushtail possums (Trichosurus vulpecula, ‘possums’), have contracted to riparian zones. Although an important possum refuge, little is known about possum population dynamics here. We examined possum population dynamics and potential drivers across two decades on the Murray River floodplain at Calperum Station. We related possum density to satellite derived fractional cover, (a measure of the proportion of green, non-green and bare ground cover), and contextualised these findings using tree condition and grazing pressure datasets. Possum surveys were conducted between 1998 and 2019 in riparian and non-riparian habitats and density was modelled in relation to fractional cover values of green, non-green, and bare ground. Possum density fluctuated between 1998 and 2008 but in 2018 and 2019, possums were undetectable. Possum density was negatively associated with bare ground and positively associated with non-green. Overgrazing by kangaroos likely reduced vegetation cover and diversity and contributed to possum decline, via a reduction in possum food resources and increased exposure to predation. Inconsistent monitoring meant that the population decline was not detected until after it had occurred, and management interventions were not triggered, highlighting the dilemma of allocating scarce monitoring resources.
... The body of work summarised here does not explore in detail the effects of some key areas of woodland bird ecology such as the impacts of pesticide use on breeding success (e.g. see Olsen et al. 1993) and the effects of abundant native herbivores such as macropods on bird occurrence (see Howland et al. 2016), or prey for birds such as invertebrate assemblages (Barton et al. 2011;Barton et al. 2009). ...
Australia’s temperate woodlands are among the most heavily modified biomes globally. I summarise some of the work on birds in south-eastern Australia that identifies drivers of bird biodiversity loss and the effectiveness of management interventions. I particularly focus on studies by the Sustainable Farms project at The Australian National University which show that: (1) Bird occurrence is associated with the amount of woody vegetation cover at site, farm and landscape scales. (2) Planting to increase woodland cover has greater relative positive effects on birds than grazing control. However, grazing of plantings has inherently negative impacts. (3) There are different broad structural types of woodland (old growth, regrowth and replantings) and each supports different bird assemblages. (4) The highest bird biodiversity occurs on farms which support all three woodland structural types, as well as other natural assets like paddock trees and fallen timber. (5) Long-term data show that while some woodland species are increasing, twice as many species are declining. Despite the body of information on woodland birds, substantial knowledge gaps remain. These include understanding of: (1) the role of fire in woodland bird dynamics and habitat suitability, and (2) demographic processes like bird breeding success and how it affects long-term site occupancy. Bird biodiversity in Australian agricultural landscapes formerly dominated by temperate woodlands will be best supported by: (1) ceasing land clearing, (2) greater woodland regeneration and woodland planting, (3) limiting livestock grazing, and (4) limiting the impacts of the Noisy Miner (Manorina melanocephala).
... There is a breadth of knowledge about the different composition of avian foraging guilds in different ecosystems including coastal systems, arid/ grassland systems, and woodland systems (Vale et al. 1982;Nally 1994). For example, foliage gleaners (insectivores) may be most dominant and show higher diversity in forested habitat cover types, generalist feeders are common in desert-shrub habitat cover types, and ground-seed feeders (granivores) are dominant in grassland habitat cover types (Vale et al. 1982;Nally 1994;Somasundaram and Vijayan 2008;Bett et al. 2016;Howland et al. 2016;Ehlers Smith et al. 2018;Kopij 2019). Seasonal shifts in the prevalence of foraging guilds may also be observed such as, in an arid grassland habitat cover type in India, insectivores were dominant during the winter season and omnivores were dominant during summer (Varun and Dutta 2020). ...
Context Habitat loss is a global problem and in Fiji >50% of the land area once covered by forests has been converted to grasslands and agricultural land. About 99% of Fiji’s endemic biodiversity and 80% of the land bird species have been identified as forest species. Aims In this study, we compare forest and grassland sites and test for consistency in avian diversity, abundance, foraging guild, and distribution status (endemic, native, introduced to Fiji) over a 5-year period (2016–2020). Methods We surveyed bird communities using the point count method with a 100 m radius and 7-min observation period per site. Key results A one-way analysis of similarities (ANOSIM) analysis showed significant differences in species composition and bird abundance between the forested habitats and grassland habitats. A general linear model test showed significant differences in foraging guild composition and distribution status between forested and grassland habitats. There were no significant differences between the three forested sites (primary montane forest, secondary old-growth forest, old-growth mahogany plantations with regenerating native species), while grassland sites had stronger annual change in species composition. Implications Forest cover, irrespective of whether these forests are of primary or secondary nature, therefore plays an important role in maintaining the native and endemic land bird species and other biodiversity in oceanic island ecosystems such as Viti Levu Island, Fiji.
... A wider survey of multiple sites under different land uses in the district suggests that this is a general response that could be expected if fertiliser inputs cease and grazing is removed (McIntyre 2008). This increase in structural diversity of the ground layer both reflects and promotes more varied grazing intensities spatially, which has benefits for both faunal and plant diversity (McIntyre et al. 2003;Howland et al. 2014Howland et al. , 2016. ...
The extent and abundance of Rytidosperma Steud. species in mixed woodland, forest and derived grassland was examined over a 15-year period following removal of long-term sheep grazing. Ground-layer vegetation in 73 permanent plots was surveyed five times between 2005 and 2020 in a 50-ha paddock on the southern tablelands of New South Wales. Sites were stratified over the slope positions and micro-habitats represented at the site. Of the 12 Rytidosperma species recorded, only R. pallidum was morphologically and ecologically distinct in the field. The remaining 11 species, termed ‘cryptic Rytidosperma’, were assessed using a novel sampling method developed for this group. Rytidosperma pallida was the only species strongly associated with sclerophyll forest habitat. The 11 other species varied in their habitat preferences but, as a group, were most dominant and persistent on upper slopes. Over the 15 years, the relative abundance of R. pilosum, R. erianthum, R. monticola, R. carphoides and R. caespitosum declined as annual exotics, native sub-shrubs and low-palatability graminoids became more dominant. But only one species (R. pilosum) significantly declined in overall frequency of presence (constancy) in the plots. The changes observed suggest that when pastoral land is converted to conservation management, reduced grazing pressure could affect the abundance of Rytidosperma species important to other species, such as the threatened moth Synemon plana.
... The impacts of peri-urban kangaroos on conservation values are well documented in the ACT, where high-density populations coincide with critically endangered ecosystems within a network of periurban reserves (ACT Government 2019a). In these environments, kangaroo grazing pressure influences the assemblage of bird species, with differential impacts depending on the life-history traits of the species (Neave & Tanton, 1989;Howland et al. 2016b). Reptile abundance, diversity and species richness are also influenced by kangaroo grazing intensity (Manning et al. 2013;Howland et al. 2014). ...
Peri-urban Eastern Grey Kangaroo (Macropus giganteus) populations can reach very high densities in areas with remnant native vegetation and adequate pasture. This review summarizes the scientific evidence for the impacts of these high-density peri-urban populations, which predominantly involve threats to human life and livelihood (kangaroo–vehicle collisions), impacts on threatened species and ecosystems and declines in the health of individual kangaroos. The latter two impacts result from an imbalance between the kangaroo population and their food resources. We argue that urban infrastructure is a fundamental driver of many of these inter-related impacts through population fragmentation, isolation and direct mortality of kangaroos on roads. Roads may also act as barriers to movement, isolating populations and promoting this localized overabundance. However, not all peri-urban kangaroo populations attain high densities. Combined with the impacts of climate change on resource availability, peri-urban development has the capacity to push local populations towards extinction in actively urbanizing areas via the impacts of habitat loss and/or fragmentation and road mortality. The successful coexistence of people and kangaroos in these peri-urban environments therefore requires a better understanding of the impacts of urban infrastructure on kangaroo population dynamics, and a better policy framework to promote ecologically sensitive development.
... Highpopulation densities of Eastern Grey Kangaroo can have serious impacts on other native species and ecosystems by causing dramatic changes in vegetation structure through overgrazing. For example, overgrazed areas have reduced habitat for ground-dwelling fauna species (Howland et al. 2016). High-density kangaroo populations can also impact the economic viability of rural enterprises (ACT Government 2017). ...
The challenge of maintaining biodiversity by managing overabundant native fauna is often a contentious issue. This study demonstrates a means of improving animal welfare in the culling of overabundant kangaroos. We studied five populations of Eastern Grey Kangaroo (Macropus giganteus) in the Australian Capital Territory and established the percentage of juveniles throughout the year. We focused on juveniles aged 8–12 months old, as these are identified at greatest risk of poor welfare outcomes if orphaned. Our findings support the timing of culls when the fewest vulnerable juveniles are present in the population. This paper provides a scientific basis for land managers to adjust the timing of kangaroo management activities to best balance animal welfare, land management and conservation objectives.
... Understanding the relationship between macropod numbers and their impacts on forage consumption , plant diversity (Morgan 2021) and wildlife habitat (e.g. Howland et al. 2016), also demands high-quality population data. ...
Every macropod population is unique in terms of the combination of species, site and management goals, so there is no universal ‘best’ method for surveying populations. We distinguish between different measures of abundance and the confidence a manager can place in them. We examine the separate components of survey methods: the survey platform, mode of detection and form of sampling. We also review the range of current methods available and highlight new developments, including their assumptions and limitations. To guide managers in choosing a method for their management context, we provide a decision matrix based on the behavioural ecology of the target species, the structure of habitat at the site and the porosity of the site boundary. To promote current best practice, we describe in detail four standard counting methods: direct count, sweep count, faecal accumulation rate and distance sampling.
... In addition to impacts on rural enterprises, overgrazing by kangaroos causes adverse impacts on biodiversity (e.g. Neave & Tanton 1989;Howland et al. 2014Howland et al. , 2016Snape et al. 2018). Continual peri-urban development, including spreading suburbs and high-speed roads, further fragments habitats and leads to more wildlife contact with humans (Coulson et al. 2014;Descovich et al. 2016;Henderson et al. 2018). ...
Macropods play an important ecological role in the Australian environment; however, at high population densities can adversely affect biodiversity and primary production and result in human–wildlife conflicts. While shooting is recognised as the most humane and species‐specific method for controlling macropod populations, in peri‐urban situations fertility control provides an attractive option to replace or reduce lethal interventions. An appropriate fertility control agent for managing overabundant macropods needs to provide long‐lasting infertility following a single treatment, be species‐specific in its action or administration method, and be safe, humane, and cost‐effective. Several contraceptive methods that induce infertility for multiple years have been tested on macropods. These include surgical techniques; hormonal implants containing deslorelin, a gonadotrophin‐releasing hormone (GnRH) agonist, or levonorgestrel, a progestin; and immunocontraceptive vaccines (zona pellucida vaccine and the GnRH‐based vaccine, GonaCon). These methods vary in the complexity of delivery and therefore their potential for adverse welfare impacts. Minimal side effects on behaviour and health have been observed. Despite some recent progress with remote dart delivery of deslorelin implants and GonaCon, efficient deployment of all existing methods is currently restricted to either captive or small, wild populations where individuals can be approached closely enough for safe capture and treatment. Of the currently available methods, levonorgestrel and GonaCon are the most suited to population‐scale management. To date, studies addressing the effect of fertility control on the growth rate of macropod populations have been limited but are essential to enable full evaluation of the efficacy and cost/benefit analysis of the different approaches. Mathematical modelling to identify the level of infertility required to meet population management goals, as well as comparing integrated management strategies, will support planning of large‐scale field trials. Improving dart delivery of existing contraceptive agents and developing new methods, such as an oral contraceptive, would increase the cost‐effectiveness of applying fertility control to free‐ranging macropods and may make treating larger populations feasible.
... Re curr ent c osts Kangaroos compete with conventional livestock for water and food, contributing significantly to grazing pressure (Waters 2018;Pahl 2019 Too many kangaroos also damage other biodiversity and ecosystem services. Research in the Australian Capital Territory (ACT) has shown that high densities of kangaroos can adversely affect a range of taxa; for example, beetle abundance and diversity are negatively affected (Barton et al. 2011), reptile abundance and occurrence are also affected by the change in grass structure (Howland et al. 2014), while the abundance of birds with grassland nesting, feeding and concealment needs is also heavily affected (Howland et al. 2016). ...
The larger kangaroos (Macropus giganteus, M. fuliginosus and Osphranter rufus) are widely distributed and have a national population which fluctuates in response to changes in grass growth and trends to 40 million. Most are outside parks and reserves and, on pastoral properties, particularly on the rangelands of southern Australia. High numbers compromise regenerative agriculture, pasture conservation, revegetation and stewardship programmes, and can have significant financial impacts on landholders by lowering livestock production and damaging sustainability. Some smaller macropods, wallabies and pademelons, also have a similar effect, especially in Tasmania and on other smaller Australian Islands where foxes are absent. Paradoxically, kangaroos have a wide range of potentially valuable production attributes and are unique, which should be a global comparative advantage. The kangaroo industry is established with a small domestic and international market, although demand has been falling in recent years. Non-commercial culling is rising, which results in millions of carcasses being wasted and left to decompose in the field. Indigenous communities abhor such waste and its cultural implications. A stronger kangaroo industry would be a better solution to managing overabundant kangaroos than pest culling and exclusion fences. Because kangaroos move from property to property, populations need to be managed on a regional basis through ‘regional property-based kangaroo production’. A form of proprietorship over this mobile resource would encourage landholders to play a role in creating greater demand for kangaroo products. They would have an incentive to raise the value of kangaroos. Through innovative harvesting, they could deliver high-quality, environmentally branded, accurately described, gourmet, differentiated products integrated with other livestock industries. They could establish cooperatives and embark on promoting regional kangaroo products. Policy improvements are needed to achieve these production systems. Doing so would diversify their enterprises, convert a liability already on their properties into an asset, create employment, enhance rural economic resilience, and improve animal welfare and conservation outcomes while earning them carbon credits. These opportunities become even more profound as climate change progresses.
... Between 1970 and2005, it is estimated that the global population of African fauna within protected areas fell by around 60% on a continental scale (Gandiwa et al., 2016;Murn et al., 2016). This is especially true for birds, whose populations have collapsed in West Africa (Howland et al., 2016;Bakker et al., 2016;Amoussou et al., 2012;Ayanlade and Proske, 2016) and in the case of the Stone Partridge, a species thought to be restricted to woody ecosystems near hills and rocky outcrops (Fretwell and Trathan, 2009). ...
... Relationships between functional traits of species and population change can offer insight into the mechanisms by which land use affects wildlife [14,15]. This understanding can be applied to produce more targeted conservation strategies and may allow for broader approaches that protect several species at once [16,17]. Functional traits can also be used to estimate the contribution of species to ecosystem services and, therefore, how those services might respond to land-use change [18]. ...
Birds are declining in agricultural landscapes around the world. The causes of these declines can be better understood by analysing change in groups of species that share life-history traits. We investigated how land-use change has affected birds of the Tasmanian Midlands, one of Australia's oldest agricultural landscapes and a focus of habitat restoration. We surveyed birds at 72 sites, some of which were previously surveyed in 1996-1998, and tested relationships of current patterns of abundance and community composition to landscape and patch-level environmental characteristics. Fourth-corner modelling showed strong negative responses of aerial foragers and exotics to increasing woodland cover; arboreal foragers were positively associated with projective foliage cover; and small-bodied species were reduced by the presence of a hyperaggressive species of native honeyeater, the noisy miner (Manorina melanocephala). Analysis of change suggests increases in large-bodied granivorous or carnivorous birds and declines in some arboreal foragers and nectarivores. Changes in species richness were best explained by changes in noisy miner abundance and levels of surrounding woodland cover. We encourage restoration practitioners to trial novel planting configurations that may confer resistance to invasion by noisy miners, and a continued long-term monitoring effort to reveal the effects of future land-use change on Tasmanian birds.
... Browsing damage by kangaroos can be particularly significant during droughts, when grass biomass is depleted ( Couslon and Norbury 1988). For several other groups, including web-spinning spiders ( Foster et al. 2015) and birds (Howland et al. 2016b), the results were more complex with some species of birds being affected and others not. ...
Since the publication of the “The Ecology of Browsing and Grazing” (Gordon and Prins, The ecology of browsing and grazing. Springer, 2008), a number of researchers have taken the approach outlined in the book to assess the impacts of differences in food and nutrient supply on the ecology of other vertebrate taxa. In line with the slightly altered emphasis of the current book (The Ecology of Browsing and Grazing II), we also asked the authors of the Sections in this Chapter to provide insights into the impacts that these different vertebrate taxa have on the ecosystems in which they exist. As you will see, the depth of research on the ecology and impacts of the different herbivorous vertebrate taxa varies considerably and demonstrates the importance of further research endeavours, on herbivore/plant interactions, across the board.
... Klink et al. (2016) found that low stocking densities favored high abundances of voles, pollinators, and flowers (van Klink, Plas, Noordwijk, WallisDeVries, & Olff, 2016). However, the bird community showed no significant responses to the grazing level (Howland et al., 2016). Biocontrol functions (predator/herbivore and parasitic wasp/herbivore ratios) were not also enhanced by the enclosure strategy in the present experiment, which indicates that complete enclosures can impede the sustainable management of steppe. ...
In recent years, the continued loss and fragmentation of steppe has caused decreased ecosystem functions and species losses in insect diversity. In the 2000s, the Chinese government developed a series of national projects, such as the construction of enclosures, to conserve natural ecosystems, including steppe. However, the effects of these enclosures on steppe arthropod community are largely unknown. In the present study, we selected enclosed and low‐grazing regions at eight National Grassland Fixed Monitoring Stations to examine the compositional differences in four insect functional groups and their associated ecological functions. The results showed that diversity significantly differed between the enclosed and low‐grazing regions, with the number of insect families being significantly higher in enclosed regions than in regions with low‐grazing pressure. The responses of the insect community to steppe management also varied among the four groups (herbivores, predators, parasitoids, and pollinators). The abundances of herbivores, predators, and parasitoids were higher in enclosed regions than in low‐grazing regions, while there was no significant difference in pollinators. Additionally, there were no significant differences in the predator/prey ratio between enclosed regions and low‐grazing regions in any of the steppe types. The parasitic wasp/prey ratio was higher in enclosed regions than in low‐grazing regions in meadow steppe and typical steppe, while there were no significant differences between the enclosed and low‐grazing regions in desert steppe and steppe desert. Herbivores were observed to benefit much more from enclosures than predators, parasitoids, and pollinators. Therefore, we recommend low‐grazing should be considered in steppe conservation, which could conserve biodiversity and achieve biocontrol functions of arthropod community.
... Both the Grassland Earless Dragon and the Striped Legless Lizard prefer a mix of short and taller grass structure (Dimond et al., 2012;Howland et al., 2016a). A mix of low and high density grazing was found to be important for diverse bird assemblages (Howland et al., 2016b). To achieve a mixed grazing effect in the absence of culled kangaroos, livestock (which have detrimental effects on native grasslands) have been used as surrogate graziers to produce the desired mix of grazed and ungrazed habitats, and to reduce bushfire hazard (Anon, 2010, p. 34). ...
Abstract Compassionate conservation is an emerging field in conservation that seeks to integrate animal protection and
conservation to achieve either improved conservation outcomes, particularly where conservation priorities and humanwildlife
conflict, or the same outcomes, but with less pain and suffering for wildlife. In the Australian Capital Territory
(ACT), Eastern Grey Kangaroos (EGKs) are culled to reduce grazing pressure on threatened native grasslands and woodlands.
We integrate decision-making criteria about animal protection into planning of wildlife-management to formulate
a compassionate conservation management case study. The management criteria include a series of guiding questions: Is
management necessary? Will intervention (management of EGKs) achieve the desired conservation outcomes? And, if
intervention is necessary, is killing necessary? We found that kangaroos can be managed without culling. The conflict between
conservation goals and kangaroo abundance is likely to be accentuated during extended drought. In the short-term,
methods for improving rates of habitat recovery can include fencing of threatened grassland communities and reduction of
kangaroo density via translocation. Human activity must also be monitored as multiple human-caused biotic and abiotic
disturbances are known to have a strong impact on biodiversity of the native grassland habitats. In the medium to longterm,
Eastern Grey Kangaroos have the potential for maintaining stable populations, and their herbivory is necessary for
grassland function and nutrient cycling. Finally, we suggest that compassionate conservation and adaptive management can
work well together as social values shift towards greater emphasis on animal protection.
... Given that increases in the abundances of red foxes and large grazers have been identified both as by-products of suppressed dingo populations and as drivers of shifts in bird assemblages, it is conceivable that bird assemblages in arid Australia could be influenced by dingo control (Letnic et al. 2012, Howland et al. 2016. In this study, we set out to identify the species, and common traits, of diurnal birds affected by functional extinctions of dingoes by surveying avian assemblages in areas where functional dingo populations persisted and areas where dingoes were functionally extinct across ~80 000 km 2 of arid dunefields. ...
We investigated how long‐term suppression of populations of a top predator, the dingo Canis dingo, affected composition of sympatric avifauna in Australian deserts, by surveying bird assemblages across ~80 000 km² of arid dune‐fields on either side of the Dingo Barrier Fence (DBF; a 5,614 km‐long fence separating ecosystems in which dingoes are abundant from ecosystems in which dingoes are functionally extinct). Using fourth‐corner modelling, incorporating species’ traits, we identified apparent declines of sedentary birds that nest in low vegetation and small birds that feed primarily on grass seed, and increases in scavenging birds associated with the functional extinction of dingoes. Occupancy differed between sites inside and outside the DBF in 13 bird species. We hypothesise that these differences in bird assemblages across the DBF result, in part, from increases in kangaroos (Macropus spp.) and red foxes (Vulpes vulpes) in arid landscapes where dingoes have been removed. Our study provides evidence that the functional extinction of a large terrestrial predator has had pervasive ecosystem effects, including shifts in composition of avian assemblages.
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... In areas where dingo populations are functionally extinct, i.e. reduced to densities at which their influence in ecosystems is negligible, kangaroo populations increase and kangaroo grazing reduces grass cover (Letnic et al., 2012). Kangaroo grazing-effects on ground-layer vegetation are most obvious in arid regions, where productivity is limited by low soil nutrients and low rainfall (Letnic et al., 2012), but also occur in mesic habitats (Howland et al., 2014;Howland et al., 2016). In arid ecosystems, bottom-up regulated populations of kangaroos could impact other species that depend on grasses for food and habitat. ...
Many examples exist of species disappearing shortly after the extinction of a previously co-occurring apex predator, however processes connecting these events are often obscure. In Australian deserts, dingo Canis dingo eradication is associated with declines in abundances of small granivorous birds, even though dingoes and these flying birds rarely directly interact. We hypothesised that dingoes facilitate small granivores by reducing populations of large, grazing kangaroos Macropus spp., thereby increasing grass seed production and availability. To test this prediction, we monitored kangaroo abundances and surveyed grass seed production and biomass of native pastures in matched, desert habitats with dingoes and where dingoes were functionally extinct. Dingo absence was associated with 99.9% greater abundances of kangaroos, 88%-98% lower pasture biomasses and 85%-97% lower densities of grass seed heads. To test that these vegetation effects were related to kangaroo grazing, we constructed large herbivore exclosures in areas where dingoes where functionally extinct and there were no grazing livestock. After three years of kangaroo exclusion, pasture biomass and grass seed production were each 87% greater than in adjacent, grazed control plots. Regeneration of vegetation within the kangaroo exclosures demonstrated that kangaroo grazing was responsible for the differences in native pastures we had observed associated with the functional extinction of dingoes. Our results indicate that reduction of grass seed availability by kangaroo grazing is a likely explanation for the relative rarity of small granivorous birds in areas where dingoes are functionally extinct. In areas where apex predators have been eradicated, reintroducing and conserving apex predators or intensively controlling mammalian herbivores would be necessary to mitigate destructive herbivory.
... Grasslands provide key services, especially in terms of food production, and key habitats for a range of biodiversity (Davis et al., 2016;Fuhlendorf et al., 2006;Howland et al., 2016) yet are currently one of the most threatened ecosystems globally (Fargione et al., 2009;Samson and Knopf, 1994;Vickery et al., 1995). Since the late 18th century, major land cover changes, such as grassland conversion to cropland and, elsewhere, woody plant encroachment, have occurred across large portions of the Great Plains in North America. ...
Grasslands are one of the most endangered ecosystems globally. Large tracts of grassland in the Great Plains, USA have been converted to cropland since the early 1900s, and woodlands are rapidly encroaching into many grasslands of the region due to changes in land management practices. Changes in the arrangement and proportion of different land cover types can affect biodiversity. We used bird survey data to identify the effect of land cover change on breeding bird ranges within the Great Plains over a 10-year period. Each species was categorized into one of the following habitat guilds: grassland, shrubland, woodland, wetland and generalist. We calculated the proportion of each land cover (including cropland, grassland, woodland, developed, barren, water bodies and wetlands) within a 1.6 km radius of each bird survey starting point. Within an occupancy modeling framework, we estimated colonization and extinction rates for each species and averaged them to the guild level. We also quantified changes in land cover from grassland to other cover types. Results show that grasslands were mostly converted to cropland and woodland, which were accompanied by positive extinction rates for certain grassland species. Extinction rates at the guild level were unrelated to increases in any land cover type, and observed land cover changes largely favored the shrubland guild. Overall, habitat-guild responses show little influence of woodland or cropland expansion at regional scales, although certain species ranges are predicted to decrease with increases in woodland. Future research should consider a finer scaled approach focusing on species-level responses when short-term land cover changes are considered.
... This work aimed to identify the main seed species consumed by Turtle Doves in a representative forest area of southern Spain. Knowledge of the main seeds included in the diet will help managers in planning grazing schemes that might increase the abundance of important seeding species in the spring (Sternberg et al. 2000, Buckingham et al. 2010, Howland et al. 2016) and, consequently, improve Turtle Dove breeding habitat in forest areas (Browne & Aebischer 2003). We also assessed the differences in diet between adult and juvenile birds in order to detect possible effects of age group on seed consumption. ...
Capsule: The diet of European Turtle Doves Streptopelia turtur in Mediterranean forest contained a large volume of wild plant seed but from a small number of key species. Aims: To determine which seed species are consumed by Turtle Doves in Mediterranean forest areas. Methods: Digestive tract contents were identified and evaluated for 222 Turtle Doves shot by hunters during three consecutive years. Results: Thirty seed species were identified in the diet, but only a few species represented most of the volume and frequency. Wild plant seeds appeared in 65.8% of digestive tracts and showed significant variation between years. Although the main wild seed species consumed each year varied annually, certain species were found in the diet every year in high volume and frequency. Adults showed a more diverse and numerous consumption of wild seeds than did juveniles. Plastic granules were also found in 3.8% of individuals. Conclusion: A greater number of wild seed species was found in the diet in contrast to previous studies performed in farmland. Echium plantagineum and Amaranthus deflexus could be important seed sources for Turtle Doves in Mediterranean forest. Additionally, the herbaceous species found in the diet whose seeds ripen earlier in the season might play an important role in Turtle Dove reproductive performance, since they are frequently the only available food in the first half of the breeding season.
... Populations of the large native grazer, the eastern grey kangaroos, Macropus giganteus, have increased in many parts of Australia over the past decade, with impacts on native biodiversity recorded (Meers & Adams 2003;McIntyre et al. 2010;Barton et al. 2011;Manning et al. 2013;Howland et al. 2016), including D. impar (Howland et al. 2014). Importantly, grazing impacts of native herbivores may provide insight into natural grazing patterns not apparent from studies of domestic livestock (Foster et al. 2014). ...
Across the globe, many species of reptile are threatened with extinction, with changes in grazing pressure as a significant factor in their decline. Few studies have investigated the role of native herbivores, yet studying natural grazers may provide insight into natural grazing regimes, not apparent in studies of domestic livestock. In this study, we investigate the habitat requirements of a threatened Australian grassland reptile, the striped legless lizard, Delma impar, in grasslands grazed by a native herbivore, the eastern grey kangaroo Macropus giganteus. Delma impar appears sensitive to habitat change resulting from altered grazing intensity, but a lack of information hinders implementation of appropriate grazing regimes. To address this gap, we investigated habitat preferences of D. impar at multiple spatial scales across a grazing gradient. We found that the occurrence of D. impar was not affected by the size of grassland remnants, but was negatively related to the density of native grazers. This result was likely a consequence of the negative effect of high grazing intensity on grass structural complexity, as the probability of encountering a D. impar was positively related to grass structural complexity at the fine scale (1 m2). We recommend that conservation efforts should avoid high intensity grazing (equivalent to > 1.3 kangaroos/ha), yet ensure enough grazing disturbance is maintained to promote the formation of complex grass structures. We also recommend that small floristically degraded and fragmented grassland habitat should be included in conservation efforts. These recommendations will likely benefit a number of faunal species in grasslands grazed by domestic and native grazers. Importantly, our data highlight the need for managing grazing regimes, even in environments dominated by native herbivores.
Wildlife management on a landscape scale is often complex, particularly where different land use practices occur in the same region. This is particularly so for the management of overabundant grazing species (both domestic and native) in a modified landscape, where anthropogenic activities and climatic drivers can influence their distribution and abundance beyond sustainable levels. In Australia’s arid rangelands, macropods benefit from pastoral activities including improved pastures, artificial watering points and the removal of apex predators. This paper addresses some of the challenges associated with managing Red Kangaroo (Osphranter rufus) in a conservation context on the privately managed Boolcoomatta Station conservation reserve in the South Australian arid rangelands. We reflect on the history of the region and how anthropogenic activities, associated with an unpredictable climate, have made macropod management so complex. Ecological monitoring at Boolcoomatta Station suggests that, along with the influence of rainfall, grazing by overabundant Red Kangaroo had a negative impact on vegetation and resident avifauna of chenopod plains. Fenced exclosures further demonstrate the grazing impact of Red Kangaroo, with perennial grasses found only where grazing was excluded. The closure of waterpoints (dams) failed to reduce Red Kangaroo impacts on the reserve, despite some evidence that persistence of Red Kangaroo near fenced dams may be reduced in the long term. Results of monitoring and management outcomes at Boolcoomatta highlight the need for an improved framework to manage Red Kangaroo. This should include consideration of improved regional stock management practices in the face of climate change; improving our understanding of the role of apex predators in agricultural landscapes; developing and setting grazing impact thresholds to instigate macropod management; improving and standardizing monitoring methods for assessing impacts; and lastly, consideration of the mental health and social well-being of land managers in these areas.
We hypothesize that the presence of cattle should increase environmental heterogeneity and therefore maintain more diverse bird communities. Therefore, we analyzed the changes in the structure of vegetation and diversity of bird species that inhabit the fluvial forests in the Delta region of the Paraná River in relation to the different cattle raising management (islands with cattle, islands without cattle, islands with recent cattle exclusion). In the islands with cattle we found lower height of the herbaceous layer, less coverage of the shrub layer and lower presence of climbing plants, which were associated with birds assemblages with greater richness, abundance and diversity. We consider that this region has evolved under a context of significant herbivory pressure, which in pre-Columbian times was possibly dominated by Blastocerus dichotomus and Ozotoceros bezoarticus (locally extinct at present), Hydrochoerus hydrochaeris and Myocastor coypus. In this context, the complete exclusion of cattle in protected areas and the absence of the cervids that inhabited this region in the past, would lead to deterioration the natural condition of the environment and seems to be generating a decrease in the diversity of these sites. We consider that a reintroduction plan for these cervids should be implemented in the area.
Recent studies suggest that apex predators play a pivotal role in maintaining healthy, balanced ecosystems. However, a criticism of studies investigating the ecological role of apex predators is that understanding does not come from manipulative experiments. Here, we use a before-after-control-impact-paired design to test predictions generated from trophic cascade theory (TCT) and mesopredator release hypothesis (MRH) by experimentally introducing dingoes into a 37km 2 paddock and measuring the resultant effects on mammal assemblages. To increase precision of parameter estimates generated by our experiment, we used a Bayesian framework which included prior information recorded from a mensurative study located in a comparable ecosystem that contrasted indices of mammal abundance where dingoes were common and rare. Results of the mensurative study were consistent with TCT and MRH. When using an uninformative prior, results of the experiment showed that dingo addition only had a negative effect on kangaroo activity. Use of an informative prior reduced uncertainty of the posterior mean parameter estimates from the experiment and suggested that red foxes were affected negatively and small mammals and rabbits were affected positively by dingo introduction. However, the prior had a strong influence on the posterior mean effect sizes for small mammals, rabbits and foxes. Opposite polarity of uninformed and prior parameter estimates for rabbits suggests that the prior was incompatible with the uninformed estimates from the manipulative experiment. Our study shows how use of logical informative priors can help to overcome statistical issues associated with low-replication in large-scale experiments, but the strong influence of the prior, means that our findings were driven largely by the mensurative study.
Significance
The island continent of Australia harbors much of the world’s most distinctive biodiversity, but this review describes an extent of recent and ongoing loss of its mammal fauna that is exceptionally high and appreciably greater than previously recognized. The causes of loss are dissimilar to those responsible for most biodiversity decline elsewhere in the world.
1. Short-term recruitment and long-term regeneration of 18 species of shrubs and trees in over 600 populations in eastern South Australia were determined by surveying membership in life history classes.2. Sites were stratified using current herbivory levels by sheep, rabbits, goats and kangaroos, past herbivory by sheep, and edaphic (soil) variables. 3. Ten species showed significant negative effects of present or past herbivory, either on recruitment, regeneration or both. Sheep grazing was the most important variable and the other herbivores frequently did not have independent effects on regeneration. 4. There was a poor relationship within a plant species between suppression of recruitment and suppression of regeneration by herbivores. The negative effects of herbivory on recruited juveniles must exceed natural thinning before overall regeneration is affected. 5. Some species showed major disruption of regeneration at sites with a history of heavy grazing during the 19th century regardless of their present responses to grazing. This evidence supports non-equilibrium models of vegetation dynamics and indicates the importance of taking historical and other non-equilibrium effects into account when designing studies of plant populations. 6. If many plant species are to avoid local extinction, it will not be sufficient to rely on controlling goats and rabbits as a conservation measure while ignoring the overriding effects of sheep grazing. The pattern of grazing use of the area will have to be modified to secure long-term conservation. A regional network of small and large reserves is suggested.
Large mammalian grazers can alter the biotic and abiotic features of their environment through their impacts on vegetation. Grazing at moderate intensity has been recommended for biodiversity conservation. Few studies, however, have empirically tested the benefits of moderate grazing intensity in systems dominated by native grazers. Here we investigated the relationship between (1) density of native eastern grey kangaroos, Macropus giganteus, and grass structure, and (2) grass structure and reptiles (i.e. abundance, richness, diversity and occurrence) across 18 grassland and grassy Eucalyptus woodland properties in south-eastern Australia. There was a strong negative relationship between kangaroo density and grass structure after controlling for tree canopy cover. We therefore used grass structure as a surrogate for grazing intensity. Changes in grazing intensity (i.e. grass structure) significantly affected reptile abundance, reptile species richness, reptile species diversity, and the occurrence of several ground-dwelling reptiles. Reptile abundance, species richness and diversity were highest where grazing intensity was low. Importantly, no species of reptile was more likely to occur at high grazing intensities. Legless lizards (Delma impar, D. inornata) were more likely to be detected in areas subject to moderate grazing intensity, whereas one species (Hemiergis talbingoensis) was less likely to be detected in areas subject to intense grazing and three species (Menetia greyii, Morethia boulengeri, and Lampropholis delicata) did not appear to be affected by grazing intensity. Our data indicate that to maximize reptile abundance, species richness, species diversity, and occurrence of several individual species of reptile, managers will need to subject different areas of the landscape to moderate and low grazing intensities and limit the occurrence and extent of high grazing.
We provide a detailed description of a fixed-radius point count method that carries fewer assumptions than most of the currently popular methods of estimating bird density and that can be used during both the nonbreeding and breeding seasons. The method results in three indices of bird abundance, any of which can be used to test for differences in community composition among sites, or for differences in the abundance of a given bird species among sites. These indices are (1) the mean number of detections within 25 m of the observer, (2) the frequency of detections within 25 m of the observer, and (3) the frequency of detections regardless of distance from the observer. The overall ranking of species abundances from a site is similar among the three indices, but discrepancies occur with either rare species that are highly detectable at great distances or common species that are repulsed by, or inconspicuous when near, the observer. We argue that differences in the behavior among species will preclude an accurate ranking of species by abundance through use of this or any other counting method in current use.
1. Little is known about hydrological influences on tropical waterbird communities. We used a 16-year data set (1991–2007) of waterbird censuses, together with a classification of observed species into foraging guilds, to explore the relationships between natural variations in flow regime, foraging guild and the community composition of waterbirds at the Okavango River in the Caprivi Strip of north-eastern Namibia, southern Africa.
2. We addressed three hypotheses to explain variation in waterbird community composition: (i) exploitation (birds move towards resource-rich patches to exploit periods of high food abundance); (ii) escapism (declines in regional habitat quality force birds to aggregate in perennial waterbodies); and (iii) interaction (bird assemblages are dominated by intra- and interspecific interactions, such as flock formation for breeding or moulting, that can be explained better by life history demands or competition than by resource availability).
3. Waterbirds in different foraging guilds responded strongly but at different periods to changes in the hydrological environment, creating a complex but predictable successional pattern in community composition through time. Deep-water feeders responded fastest (abundance peaking 2 months post-flood), followed by shallow-water feeders (4 months) and emergent vegetation feeders (7 months). Species that forage on short vegetation or in mud showed a bimodal response with peaks in abundance at 3 and 8 months post-flood.
4. Our results indicated a strong effect of the local flow regime and hence supported the exploitation hypothesis. The foraging guild approach allowed us to identify clear patterns in a highly complex ecosystem and shows considerable promise as an analytical tool for similar data sets. Our results further suggest that while the entire bird community will be affected by hydrological alterations such as impoundments, water extraction and climate change, deep-water feeders may be one of the most vulnerable groups.
We establish a methodology and present baseline data for a long-term grassy woodland restoration study that commenced in 2007 in two nature reserves (Mulligans Flat, Goorooyarroo (35° 9–13’ S; 149° 9–12’ E)) totalling 1386 ha on the northern boundary of Canberra, in the Australian Capital Territory in south eastern Australia. The experimental infrastructure comprises 96 × 1 ha sites established in Eucalyptus blakelyi / Eucalyptus melliodora dominated woodland. These are being subjected to varying kangaroo grazing pressure and augmentation with logs, while burning treatments are planned. One reserve (Mulligans Flat) has been fenced for feral predator control and contains half the sites, forming a companion experiment to Goorooyarroo. Our baseline floristic study comprised estimates, at the site
level, of ground layer biomass, species biomass, ground cover types and soil (0–10 cm) properties. From these data we conclude that the groundlayer vegetation is dominated by Joycea pallida, Austrodanthonia spp., Themeda australis and Aristida ramosa. These grasses varied in abundance according to differences in soil pH, phosphorus and to a lesser extent nitrates. Forb frequencies were highly sensitive to nitrate levels with annual exotic forbs dominating at high nitrate sites. More generally, soil nutrient levels and exotic species in some sites indicated areas of previous pasture improvement activities. Biomass estimates indicated extremely high grazing pressure, sufficient to negatively affect the habitat quality for ground-dependent fauna and some soil processes. These data will provide an important basis for examining rates of ecosystem recovery under different restoration strategies.
Identifying the relationships between species traits and patch-scale vegetation characteristics in areas designated for urban development can improve our understanding of how animal communities may change with urbanization. We explored the implications of this premise to the urban planning process in a mixed-use landscape in Canberra (Australia), prior to its development into new suburbs. We used RLQ analysis to relate bird foraging, nesting and body size traits to patch-scale vegetation characteristics. Relationships between species traits and vegetation characteristics within the development zone suggest that species that forage and nest on the ground and in the understory strata, and smaller-bodied species will be most negatively affected by urbanization. Identifying the relationships between species traits and vegetation characteristics may be used by urban planners to (i) identify potentially critical habitat and species at risk from development, (ii) inform the choice of impact mitigation measures, and/or (iii) distinguish between high and low mitigation measures. Analyses conducted early in the planning process can then be used to allocate proposed land uses in an ecologically sensitive way, and to plan appropriate mitigation measures.
Natural resource managers have used natural variability concepts since the early 1960s and are increasingly relying on these concepts to maintain biological diversity, to restore ecosystems that have been severely altered, and as benchmarks for assessing anthropogenic change. Management use of natural variability relies on two concepts: that past conditions and processes provide context and guidance for managing ecological systems today, and that disturbance-driven spatial and temporal variability is a vital attribute of nearly all ecological systems. We review the use of these concepts for managing ecological systems and landscapes. We conclude that natural variability concepts provide a framework for improved un- derstanding of ecological systems and the changes occurring in these systems, as well as for evaluating the consequences of proposed management actions. Understanding the history of ecological systems (their past composition and structure, their spatial and temporal variability, and the principal processes that influenced them) helps managers set goals that are more likely to maintain and protect ecological systems and meet the social values desired for an area. Until we significantly improve our understanding of ecological systems, this knowledge of past ecosystem functioning is also one of the best means for predicting impacts to ecological systems today. These concepts can also be misused. No a priori time period or spatial extent should be used in defining natural variability. Specific goals, site-specific field data, inferences derived from data collected elsewhere, simulation models, and explicitly stated value judg- ment all must drive selection of the relevant time period and spatial extent used in defining natural variability. Natural variability concepts offer an opportunity and a challenge for ecologists to provide relevant information and to collaborate with managers to improve the management of ecological systems.
Community ecological theory may play an important role in the development of a science of restoration ecology. Not only will the practice of restoration bene- fit from an increased focus on theory, but basic re- search in community ecology will also benefit. We pose several major thematic questions that are rele- vant to restoration from the perspective of community ecological theory and, for each, identify specific areas that are in critical need of further research to advance the science of restoration ecology. We ask, what are appropriate restoration endpoints from a community ecology perspective? The problem of measuring resto- ration at the community level, particularly given the high amount of variability inherent in most natural communities, is not easy, and may require a focus on restoration of community function (e.g., trophic struc- ture) rather than a focus on the restoration of particu- lar species. We ask, what are the benefits and limita- tions of using species composition or biodiversity measures as endpoints in restoration ecology? Since reestablishing all native species may rarely be possi- ble, research is needed on the relationship between species richness and community stability of restored sites and on functional redundancy among species in regional colonist "pools." Efforts targeted at restoring system function must take into account the role of in- dividual species, particularly if some species play a disproportionate role in processing material or are strong interactors. We ask, is restoration of habitat a sufficient approach to reestablish species and func- tion? Many untested assumptions concerning the rela- tionship between physical habitat structure and resto- ration ecology are being made in practical restoration efforts. We need rigorous testing of these assump- tions, particularly to determine how generally they apply to different taxa and habitats. We ask, to what extent can empirical and theoretical work on commu- nity succession and dispersal contribute to restoration ecology? We distinguish systems in which succession theory may be broadly applicable from those in which it is probably not. If community development is highly predictable, it may be feasible to manipulate natural succession processes to accelerate restoration. We close by stressing that the science of restoration ecology is so intertwined with basic ecological theory that practical restoration efforts should rely heavily on what is known from theoretical and empirical re- search on how communities develop and are struc- tured over time.
Habitat structure is a major determinant of bird species diversity. One process by which habitat structure is altered is livestock grazing, the most extensive land use across most continents. While the impacts of grazing on vegetation have received much attention, the effects on avifauna are less well known.
Predictions of the impact of grazing on Australian woodland and riparian bird assemblages were formulated. We used available information on the vegetation strata utilized by each species for foraging and the strata most affected by grazing.
We compared predictions based on foraging height preferences with differences in bird density in grassy eucalypt woodland and riparian habitats subject to three levels of grazing. We found that foraging height preference was a good predictor of species’ susceptibility to grazing. Birds exhibited both monotonic and non‐monotonic responses to grazing, with the majority of bird species declining with increasing grazing pressure.
Synthesis and applications . Existing information on foraging behaviour can be used to make predictions of the impact of any threat on birds where that threat alters habitat structure. While the approach is simple, it is a point of departure for more complex predictive models, and avoids the circularity of post hoc interpretation of impact data. This approach can be used to guide management decisions where landscapes are in a state of transition and species conservation is a priority.
Livestock grazing is the dominant land use in the remaining seminatural grasslands in Europe. Abandonment of grasslands and, conversely, intensified grazing by livestock have been suggested as possible causes for the widespread population declines of many farmland birds, although the direct impact of grazing on farmland birds is poorly known. Here, we use a comprehensive, long-term data set (20 pastures surveyed over five years) to test the effects of changes in grazing intensities in seminatural dry pastures on between-year variation of the farmland bird community, functional groups of species, and individual species. Bird communities in all 20 seminatural pastures showed a low degree of temporal variability (Kendall's coefficient of concordance on ranked abundances: mean W = 0.72, range = 0.58-0.89). Community variability was not significantly related to site area, grazing pressure, vegetation structure, or adjacent habitat composition. However, analyses of functional groups of species categorized according to body mass and breeding diet showed that different species subsets had differential responses to between-year changes in grazing pressure (as reflected by changes in grass height). Local extinction and recol- onization of ground-feeding insectivorous bird species were affected by yearly changes in grazing pressure, but there was no effect of grazing on ground-feeding species that fed on a mixed diet or on species that foraged in trees and shrubs. In general, large insectivores (>30 g) preferred moderately grazed pastures, and small insectivores (-30 g) preferred pastures with intensive grazing pressure. We propose that current intensive grazing should be relaxed (i.e., by reducing the number of stock per hectare or by within-season rotational grazing) so that with a given stock size, larger areas of seminatural dry pastures could be grazed. This would decrease the rate of habitat loss and conserve a larger part of the farmland bird community breeding in this habitat.
Grazing history alone is not a good predictor of plant-herbivore interactions. Interactions occur along gradients of convergent to divergent selection pressures with increasing environmental moisture and of intolerance to tolerance of grazing with increasingly long evolutionary histories of grazing. Feedback mechanisms between plants and grazing animals are well developed in grasslands with long evolutionary histories of grazing. Feedback mechanisms are manifest in the rapid switching capabilities (of plant species and modes of competition) of subhumid grasslands with long evolutionary histories of grazing and divergent selection pressures. Switching capabilities do not exist in semiarid grasslands with long evolutionary histories of grazing and convergent selection pressures. Rather, for heavily grazed dominant species dominance increases. Feedback mechanisms are not well developed in systems with short evolutionary histories of grazing. Here, differences in response to grazing by semiarid and subhumid situations arise primarily from differences in the grazing tolerance of plants adapted to semiaridity or of plants adapted to competition for light and from the different effects of grazing on canopy structure. -from Authors
1. High densities of vertebrate herbivores can be a significant barrier to ecological restoration in many parts of the world because of their impact on vegetation biomass. A common method for managing vertebrate herbivores is the use of exclosure fences, but very few studies have examined how small-scale structural refugia (e.g. logs) can mitigate grazing impacts. We examined how beetles responded to experimentally manipulated kangaroo Macropus giganteus grazing levels using both exclosure fences and addition of logs over a 16-month period.
We consider hierarchical generalized linear models which allow extra error components in the linear predictors of generalized linear models. The distribution of these components is not restricted to be normal; this allows a broader class of models, which includes generalized linear mixed models. We use a generalization of Henderson's joint likelihood, called a hierarchical or h‐likelihood, for inferences from hierarchical generalized linear models. This avoids the integration that is necessary when marginal likelihood is used. Under appropriate conditions maximizing the h‐likelihood gives fixed effect estimators that are asymptotically equivalent to those obtained from the use of marginal likelihood; at the same time we obtain the random effect estimates that are asymptotically best unbiased predictors. An adjusted profile h‐likelihood is shown to give the required generalization of restricted maximum likelihood for the estimation of dispersion components. A scaled deviance test for the goodness of fit, a model selection criterion for choosing between various dispersion models and a graphical method for checking the distributional assumption of random effects are proposed. The ideas of quasi‐likelihood and extended quasi‐likelihood are generalized to the new class. We give examples of the Poisson–gamma, binomial–beta and gamma–inverse gamma hierarchical generalized linear models. A resolution is proposed for the apparent difference between population‐averaged and subject‐specific models. A unified framework is provided for viewing and extending many existing methods.
The technique of iterative weighted linear regression can be used to obtain maximum likelihood estimates of the parameters with observations distributed according to some exponential family and systematic effects that can be made linear by a suitable transformation. A generalization of the analysis of variance is given for these models using log- likelihoods. These generalized linear models are illustrated by examples relating to four distributions; the Normal, Binomial (probit analysis, etc.), Poisson (contingency tables) and gamma (variance components).
The implications of the approach in designing statistics courses are discussed.
We examined the similarities and differences in the foraging patterns of 22 insectivorous bird species during their breeding season in the Hubbard Brook Experimental Forest, New Hampshire, USA. Using multivariate techniques (clustering of hyperdimensional Euclidean distances, principal components analysis, and Varimax rotated factor analysis), we distinguish 4 groups of species or guilds, each of which exploits food resources in a distinctly different way. Partitioning occurs primarily by (1) foraging height and height-related characters, (2) foraging locations within the forest canopy, and (3) differential use of tree species, foraging substrates and foraging maneuvers. The results indicate that the importance of vegetation height to bird species diversity is related (1) to foraging opportunities which differ along a gradient from ground level to the upper canopy and which are roughly indexed by measures of foliage height diversity (FHD), and (2) to the presence of the supporting branch and bole framework which provides a major distinct foraging region. We suggest that foraging opportunities vary with height in a forest and are influenced by the physical and chemical characteristics of the plant species, which in turn affect the kinds and distributions of foraging substrates, the ways in which birds search for and find food, and the abundances of food resources. The implications of these findings for understanding the structure of forest bird communities are discussed.
Systematics and Taxonomy of Australian Birds presents an up-to-date classification of Australian birds. Building on the authors’ 1994 book, The Taxonomy and Species of Birds of Australia and its Territories, it incorporates the extensive volume of relevant systematic work since then. The findings of these studies are summarised and evaluated in the explanations for the taxonomic treatments adopted, and with the extensive citations, the book serves as a comprehensive introduction to the recent systematic literature of Australian birds. All species of birds that have been recorded from the Australian mainland, Tasmania, island territories and surrounding waters are treated and listed. Along with extant native species, all accepted vagrants, recently extinct (since 1800) native species and established introduced species are included.
Disturbance is an important component of many ecosystems, and variations in disturbance regime can affect ecosystem and community structure and functioning. The “intermediate disturbance hypothesis” suggests that species diversity should be highest at moderate levels of disturbance. However, disturbance is also known to increase the invasibility of communities. Disturbance therefore poses an important problem for conservation management, Here, we review the effects of disturbances such as fire grazing, soil disturbance and nutrient addition on plant species diversity and invasion with particular emphasis on grassland vegetation. Individual components of the disturbance regime can have marked effects on species diversity, but it is often modifications of the existing regime that have the largest influence. Similarly, disturbance can enhance invasion of natural communities, but frequently it is the interaction between different disturbances that has the largest effect. The natural disturbance regime is now unlikely to persist within conservation areas since fragmentation and human intervention have usually modified physical and biotic conditions. Active management decisions must now be made on what disturbance regime is required and this requires decisions on what species are to be encouraged or discouraged.
Large mammalian herbivores are major drivers of the structure and function of terrestrial ecosystems world‐wide, and changes in their abundance have resulted in many populations being actively managed. Many empirical studies have identified that abundant mammalian herbivores can have negative impacts on biodiversity, but there has been no specific review of the impacts of native mammalian herbivores.
We assessed the peer‐reviewed literature on the effects of large native herbivores on other animals. We aimed to quantitatively synthesize current knowledge, identify gaps and limitations in the literature, and highlight priorities for future research.
Most empirical studies of herbivory effects compared only two levels of herbivory (76%), and meta‐analysis showed that very high densities of herbivores, when compared with very low densities, had mostly negative effects on other animal species. These negative effects were usually attributed to changes in the quantity and/or structure of vegetation. Only 24% of papers studied animal responses across a gradient of herbivore densities, and nonlinear responses to herbivory, as well as responses to low and moderate herbivore densities, remain poorly understood.
The literature also was dominated by short‐term studies (76% sampled animal responses for 2 years or less), and there was a high incidence of confounding factors among studies (38% of studies). In addition, many studies used only coarse metrics to assess effects (e.g. only 33% of studies assessed species composition) and few included community‐level synthesis (only 31% of studies reported results from more than one animal class).
Synthesis and applications . Critical questions remain for both basic ecology and the management of large native herbivores for biodiversity. Key knowledge gaps include (i) nonlinear responses to herbivore pressure, (ii) how responses differ between different herbivores, (iii) the spatial and (iv) the temporal variation of responses, (v) how the effects of herbivores interact with other land management activities and (vi) the mechanisms driving cascading effects through ecosystems. We identify ways to address these gaps and emphasize the need for studies which employ contrasts over a gradient of ecologically relevant herbivore densities and biologically meaningful time frames.
Evaluating the effectiveness of protected areas for sustaining biodiversity is crucial to achieving conservation outcomes. While studies of effectiveness have improved our understanding of protected-area design and management, few investigations (< 5%) have quantified the ecological performance of reserves for conserving species. Here, we present an empirical evaluation of protected-area effectiveness using long-term measures of a vulnerable assemblage of species. We compare forest and woodland bird diversity in the Australian Capital Territory over 11 yr on protected and unprotected areas located in temperate eucalypt woodland and matched by key habitat attributes. We examine separately the response of birds to protected areas established prior to 1995 and after 1995 when fundamental changes were made to regional conservation policy. Bird diversity was measured in richness, occurrence of vulnerable species, individual species trajectories and functional trait groups. We found that protected areas were effective in maintaining woody vegetation cover in the study region, but were less effective in the protection of the target bird species assemblage. Protected areas were less species rich than unprotected areas, with significant declines in richness across sites protected prior to 1995. Small, specialised and vulnerable species showed stronger associations with unprotected areas than protected areas. Our findings indicate that recently established reserves (post-1995) are performing similarly to unprotected woodland areas in terms of maintaining woodland bird diversity, and that both of these areas are more effective in the conservation of woodland bird populations than reserves established prior to 1995. We demonstrate that the conservation value of protected areas is strongly influenced by the physical characteristics, as well as the landscape context, of a given reserve and can diminish with changes in surrounding land use over time. Both protected areas and off-reserve conservation schemes have important roles to play in securing species populations.
Aim
Management practices in the landscape matrix can have significant effects on the spatial distribution of animals within adjacent protected areas. This has been well established in agricultural and forested areas, but less is known about how management of the suburban matrix affects adjacent reserves. We argue that it is critically important to understand the impact of suburban management on reserves, as flawed planning decisions can have negative conservation outcomes and waste limited resources.
Location
Canberra, Australian Capital Territory, Australia.
Methods
We examined bird distribution patterns in suburbs and adjacent reserves to the effects of two suburban management practices: (1) street tree planting and (2) boundary design. We focused on three groups of birds with known responses to urbanization: native urban‐intolerant species (native avoiders), native urban‐tolerant species (native adapters) and exotic urban‐tolerant species (exotic adapters).
Results
We found that suburbs with ≥30% native ( Eucalyptus ) street trees and reserves adjacent to these suburbs had significantly higher bird species richness, native adapter species richness and probability of reporting exotic adapters than those with exotic trees. The type of street trees, however, did not affect the probability of reporting native avoiders. These species were more likely to be reported when habitat complexity was high. Only native adapters responded to boundary design, with higher species richness when the boundary type was a local or unsealed road as opposed to an arterial road.
Main conclusions
Native street trees provide foraging resources for birds that would be reduced or absent in exotic streetscapes, enabling native streetscapes to support a rich community of birds. Furthermore, native streetscapes increase bird richness and diversity in adjacent reserves. This result has important conservation implications for suburb and reserve management practices. Our study provides evidence that the establishment and retention of native suburban streetscapes is an important management strategy for improved bird conservation.
We consider hierarchical generalized linear models which allow extra error components in the linear predictors of generalized linear models. The distribution of these components is not restricted to be normal; this allows a broader class of models, which includes generalized linear mixed models. We use a generalization of Henderson's joint likelihood, called a hierarchical or h-likelihood, for inferences from hierarchical generalized linear models. This avoids the integration that is necessary when marginal likelihood is used. Under appropriate conditions maximizing the h-likelihood gives fixed effect estimators that are asymptotically equivalent to those obtained from the use of marginal likelihood; at the same time we obtain the random effect estimates that are asymptotically best unbiased predictors. An adjusted profile h-likelihood is shown to give the required generalization of restricted maximum likelihood for the estimation of dispersion components. A scaled deviance test for the goodness of fit, a model selection criterion for choosing between various dispersion models and a graphical method for checking the distributional assumption of random effects are proposed. The ideas of quasi-likelihood and extended quasi-likelihood are generalized to the new class. We give examples of the Poisson-gamma, binomial-beta and gamma-inverse gamma hierarchical generalized linear models. A resolution is proposed for the apparent difference between population-averaged and subject-specific models. A unified framework is provided for viewing and extending many existing methods.
The alarming rate of ecosystem degradation has raised the need for ecological restoration throughout different biomes and continents. North European forests may appear as one of the least vulnerable ecosystems from a global perspective, since forest cover is not rapidly decreasing and many ecosystem services remain at high level. However, extensive areas of northern forests are heavily exploited and have lost a major part of their biodiversity value. There is a strong requirement to restore these areas towards a more natural condition in order to meet the targets of the Convention on Biological Diversity. Several northern countries are now taking up this challenge by restoring forest biodiversity with increasing intensity. The ecology and biodiversity of boreal forests are relatively well understood making them a good model for restoration activities in many other forest ecosystems. Here we introduce northern forests as an ecosystem , discuss the historical and recent human impact and provide a brief status report on the ecological restoration projects and research already conducted there. Based on this discussion, we argue that before any restoration actions commence, the ecology of the target ecosystem should be established with the need for restoration carefully assessed and the outcome properly monitored. Finally, we identify the most important challenges that need to be solved in order to carry out efficient restoration with powerful and long-term positive impacts on biodiversity: coping with unpredictability, maintaining connectivity in time and space, assessment of functionality, management of conflicting interests and social restrictions and ensuring adequate funding.
1. With world‐wide changes in human land use, an important challenge for conservation biologists is to develop frameworks to predict how species will respond to landscape change. Environmental filtering, where different environments favour different species’ traits, has the potential to be a useful predictive framework. Therefore, it is important to advance our understanding of how species with different traits respond to environmental variables.
2. We investigated the distribution of microbats in a 1 000 000 ha agricultural region in southeastern Australia, with specific emphasis on the effects of tree density on bat species characterized by different sizes, wing shapes and echolocation frequencies. The study area is substantially cleared, and trees are continuing to decline because grazing inhibits tree regeneration. We monitored bat activity acoustically at 80 sites spanning a wide range of tree densities. We used regression modelling to quantify the response of bats to tree density and other ecological covariates, and RLQ analysis to assess how different traits correlated with various environmental gradients.
3. Total bat activity and species richness peaked at intermediate tree densities. Species composition was explained by tree density and the traits of individual species. Sites with low tree cover were dominated by large, fast‐flying species, whereas sites with dense tree cover were dominated by smaller, highly manoeuvrable species. These findings are consistent with recent findings from other locations around the world.
4. Synthesis and applications. Trait‐based predictive frameworks enable landscape managers to assess how different management strategies and landscape modifications are likely to affect different species. Here, we propose a framework to derive general predictions of how bats respond to landscape modification, based on tree density and species traits. We apply this framework to a current conservation issue of tree decline in our study area and derive management priorities including: (i) maintaining a range of tree densities throughout the region; (ii) ensuring the persistence of locations with intermediate tree densities; and (iii) using environmentally sensitive grazing practices, for example, by incorporating long rest periods.
Restoration projects often do not effectively restore some key biological resources that take time, often centuries, to accumulate. Such resources are often characteristic of ‘natural’ ecosystems and are critical to successful ecosystem recovery. Deadwood or ‘coarse woody debris’ (CWD) is one such example. Coarse woody debris is depauperate in many of the world’s ecosystems due to stand structural simplification through vegetation clearing, logging and grazing. The lag time in the natural accumulation of CWD can be a major barrier to their effective ecological restoration in the short term. We examined the effect of experimentally adding CWD, in four different treatments, on reptile abundance in temperate woodlands in south-eastern Australia – one of the most highly degraded vegetation types on the continent. We then investigated the influence that varying grazing pressure and vegetation density had on those effects. We examined three key questions: (1) Does the addition of CWD change overall reptile abundance over a 4 year period? (2) Does existing vegetation density or kangaroo grazing effect reptile response? (3) Is there evidence of high order interaction effects between CWD, kangaroo grazing and vegetation density on reptile response? Adding CWD increased reptile abundance significantly after only 4 years. The spatial pattern of CWD distribution also significantly affected reptile abundance. The location where CWD was added also was important, with open and mid-dense vegetation gaining the highest number of small skinks compared to control sites. Reduction of grazing was the most effective way of increasing small skink abundance in high density vegetation. Open areas gained most from the addition of CWD where high kangaroo grazing occurred. We conclude that adding CWD can short-cut a 100–200 year barrier to ecosystem restoration. By distributing CWD in particular patterns and places in the landscape, and in combination with different grazing levels, conservation managers can improve effectiveness of restoration programs.
Do sites managed under an agri-environment scheme support significantly more biodiversity than sites managed in accordance with traditional agricultural practices? This is a key question underpinning agri-environment schemes worldwide, including one that we report on here that has been established in south-eastern Australia. To address this question, we established a large-scale, blocked and replicated cross-sectional study comprising 104 sites in four key “management” classes: (1) Agricultural production sites characterized by traditional set-stocking grazing. (2) Short-term conversion sites in which investments to improve conservation had recently (<2 years ago) been made. (3) Long-term conversion sites where investments to improve conservation values were made >7 years ago. And (4) Traveling stock reserves (TSRs) which have traditionally been subject to limited vegetation clearing and grazing pressure over the past 150 years. Such TSRs are often considered ‘benchmarks’ of vegetation condition and biodiversity prior to European settlement.
Work in many parts of the world has discussed the decline of biodiversity in regions dominated by agriculture. We report the results of a major study documenting the longitudinal profiles of birds between 1998 and 2009 within 66 patches of temperate woodland in a heavily cleared and grazed agricultural region of south-eastern Australia. Many researchers have forecast the loss of bird biota from this region and others that also were formerly dominated by temperate woodland.We had sufficient high quality data to analyse the longitudinal profiles of reporting rates for 76 of the 116 individual bird species recorded in our 12-year study. Unexpectedly, only four of the 76 species analysed (5.6%) exhibited a significant negative linear decrease in reporting rate. More surprisingly, 32 (42.1%) exhibited a significant positive linear increase in reporting rate, including several taxa of conservation concern. These increases occurred despite a series of below-average rainfall years. Reporting rates were too low to formally model long-term trends in some other bird species widely considered to be of conservation concern such as the Diamond Firetail (Stagonopleura guttata) and Speckled Warbler (Chthonicola sagittata).Many authors have used functional (and other) groups to forecast bird species likely to be lost from Australia’s temperate woodlands. However, we found no clear links between life history attributes and long-term trend patterns of species.Our findings contrast with recent findings from other temperate woodland-dominated regions in eastern Australia where losses in bird populations have been documented. However, they parallel other investigations such as in central New South Wales. These similarities among, and differences between, studies suggest regional differences in temporal patterns in bird population dynamics. Many of the observed changes in reporting rates were positive and they provide hope that forecast future losses of a large proportion of existing temperate woodland bird assemblages in south-eastern Australia may not be realised uniformly in all regions.
In a grassland–oak savanna in southeastern Arizona, we compared vegetative ground cover and bird populations between a 29-year livestock exclosure and an adjacent cattle ranch that was managed according to the principles of holistic resource management, including short-duration rotational grazing. The study took place in the winter after a 2-year drought and 1 year after the drought ended and stocking densities were reduced. During the first winter, grasses on the livestock exclosure were taller (4.4 times) and had higher basal area ground cover (2.5 times), canopy cover (2.2 times), and reproductive canopy cover (10 times) than in the grazed area. These differences persisted into the second winter but at lower levels. As a group, 19 species of ground-foraging, seed-eating birds (e.g., doves, quail, sparrows, towhees) were 2.7 times more abundant on the exclosure than on adjacent grazed grasslands during the first winter. These same species were 1.7 times more abundant on the exclosure during the second winter and were 2.9 times more abundant on both sites combined after the drought had ended. A second group of 24 avian species with different foraging ecologies (e.g., predators, frugivores, arboreal insectivores) did not differ between treatments or years. High-density, short-duration rotational grazing, coupled with a drought, left the land in a substantially denuded condition through two winters and negatively affected a variety of resident and migratory birds dependent on ground cover and seed production for over-winter survival.
Over a 10-y period, eastern and western grey kangaroos were bred in enclosures. All western subspecies interbred, and western males bred with eastern females to give hybrid young, but never the reverse cross. Hybrid males were sterile but females readily backcrossed with western males. Mean gestation lengths were: eastern greys, 36.41 ± 1.63 days; western greys, 30.56 ± 2.55 days; hybrids, 34.09 ± 0.81 days; backcrosses, 31.58 ± 0.93 days.
Births occurred throughout the year in both species, but those of western greys were more concentrated in the summer months. Gestation length did not vary with month of year. Parturition in one backcross female is described.
Young weighed just over 800 mg at birth and could reach 1000 mg within 24 h. With a free
choice, they preferred an anterior to a posterior teat, but when one teat was already being suckled, they chose either the anterior or the posterior teat on the opposite side. The sex ratio was close to unity in all groups, the overall value being 102B : 100@.
If dropped from the pouch, young of all groups over 200 days old (mean minimum age 243.86 ± 19.74 days) were usually capable of standing and regaining the pouch. Eastern and western young left the pouch for the first time at mean ages of 283.86 ± 24.70 and 298.40 ± 34.29 days respectively,and left it finally at about 320 days old in both species. Within the western species, pouch life was significantly longer in the subspecies ocydromus than in either fuliginosus or melanops.
The intervals between parturitions in lactating females was close to 1 year (variation between species was probably significant). The mean interval in eastern females undergoing embryonic diapause did not differ significantly from that in western females not doing so; in western females it did not differ significantly between fuliginosus and ocydromus, but did so between melanops and both the other subspecies. Lactation usually exceeded 18 months.
Mortality of pouch young accounted for 17% of known births, mostly within the first few days after birth. Accidental injury and coccidiosis were the major causes of death in the first months after leaving the pouch.
We observed the effect of several flock and extrinsic variables on the vigilance and foraging behaviour of red-rumped parrots, Psephotus haematonotus (Gould), and galahs, Cacatua roseicapilla (Vieillot), during the non-breeding and early breeding season in the Canberra region. Birds devoted less time to vigilance and more to foraging as flock size increased. However, log-linear modelling revealed that this relation was affected by a complex set of variables, inevitably in the direction of higher vigilance as predation risk increased. Although both species adjust scan rates, red-rumped parrots were more likely to adjust the length of scans than galahs, possibly because the opportunity to increase scan rates is restricted when scan rate is already high. Changes to food resources and the physiological demands of winter cause adjustments to the diurnal pattern of foraging, but not to the total time spent foraging, or to the pattern of flocking. We conclude that the risk of predation is the dominant influence on flocking by parrots.
This paper describes a new method for estimating pasture yield in which the yields of random quadrats are rated with respect to a set of reference quadrats preselected in the field to provide a scale which is available for reference throughout the sampling. Three alternative calibration procedures are described based either on the dry matter yields of the reference quadrats or on the yields of quadrats rated and cut either during or at the end of sampling. The second and third procedures are shown to have advantages over the first. When testing the method with four observers and two types of calibration scales, estimates of mean yield were generally within 4 per cent of the actual mean with a maximum difference of 8 per cent. Methods are given for calculating the number of samples required to obtain minimum variance for the estimate of mean yield for a given cost in terms cf time spent in the field.
This paper describes a new method for estimating pasture yield in which the yields of random quadrats are rated with respect to a set of reference quadrats preselected in the field to provide a scale which is available for reference throughout the sampling. Three alternative calibration procedures are described based either on the dry matter yields of the reference quadrats or on the yields of quadrats rated and cut either during or at the end of sampling. The second and third procedures are shown to have advantages over the first. When testing the method with four observers and two types of calibration scales, estimates of mean yield were generally within 4 per cent of the actual mean with a maximum difference of 8 per cent. Methods are given for calculating the number of samples required to obtain minimum variance for the estimate of mean yield for a given cost in terms cf time spent in the field.
The diet of the eastern grey kangaroo and wallaroo was compared at 2 sites, Lana and Newsholme, in the New England tablelands of New South Wales. At Lana, the pastures had been fertilized for 20 yr and were dominated by low-fibre grasses such as Bothriochloa, Eragrostis, Sporobolus, Microlaena, Danthonia and Vulpia; some paddocks had been sown with introduced grasses, Phalaris, Festuca and lucerne. Coarse tussock grasses such as Poa spp., Stipa and Danthonia pallida predominated at Newsholme. The major difference in the diet of the 2 spp. was in winter when individuals on the unimproved area at Newsholme ate a higher proportion of tussock grasses and less low-fibre grass. Both spp. consistently selected for low-fibre grass leaf; they did not differ in their use of plant parts. The diets contained many plant spp. in common, although there were major differences in the use of several spp. The plant spp. favoured only by the wallaroo were of a higher quality than those favoured only by the grew kangaroo.
Forests and grassy vegetation (savannas and grasslands) are alternative ecosystem states in many tropical landscapes. Relative to forests the grassy ecosystems are poorly known and poorly conserved, partly because they were thought to be products of forest clearance. However many grasslands have proved to be ancient. Commensurate with their antiquity, grassy biomes have distinct suites of plant and animal species that contribute a large fraction of the diversity of forest–grassland mosaics. Grasslands differ strikingly from forests in their ecology and in the nature of threats to their future. Here we highlight the high biodiversity value of grassy biomes and, in contrast to tropical forests, we illustrate the importance of fire in maintaining these systems. We discuss the major threats to, and consequences for, biodiversity in these regions including land clearance and elevated CO2-driven forest expansion. Finally we focus on the difficulties of grassland restoration. A new approach to understanding and conserving grassy ecosystems, free from cultural prejudices of the past, is long overdue.
This review considers the history of the discovery of the rabbit haemorrhagic disease virus (RHDV) and its spread throughout the world in domestic and wild rabbits, which led eventually to its deliberate release into Australia and New Zealand for the control of a major pest, the introduced wild rabbit. The physical and genetic structure of RHDV is now well understood, and its pathogenic effects are also well known. The epidemiology of rabbit haemorrhagic disease (RHD) has been clearly documented in the field in European countries, Australia and New Zealand. Since its initial spread through largely naïve populations of wild rabbits it has established a pattern of mainly annual epizootics in most areas. The timing of epizootics is dependent on climatic variables that determine when rabbits reproduce and the appearance of new, susceptible rabbits in the population. The activity of RHDV is also influenced by climatic extremes that presumably affect its persistence and the behaviour of insect vectors, and evidence is growing that pre-existing RHDV-like viruses in some parts of Australia may interact with RHDV, reducing its effectiveness. The timing of epizootics is further modified by the resistance to RHD shown by young rabbits below 5 weeks of age and the presence of protective maternal antibodies that also protect against fatal RHD. RHD has reduced rabbit abundance, particularly in dry regions, but rabbits in cooler, high-rainfall areas have been able to maintain their populations. In Australia and New Zealand, RHD has raised the prospects for managing rabbits in low rainfall areas and brought substantial economic and environmental benefits. W R02010 RHD and t he biologi cal con tr ol of wi ld ra bbi ts B. Co o ke and F. Fe nner
The technique of iterative weighted linear regression can be used to obtain maximum likelihood estimates of the parameters with observations distributed according to some exponential family and systematic effects that can be made linear by a suitable transformation. A generalization of the analysis of variance is given for these models using log-likelihoods. These generalized linear models are illustrated by examples relating to four distributions; the Normal, Binomial (probit analysis, etc.), Poisson (contingency tables) and gamma (variance components). The implications of the approach in designing statistics courses are discussed.
The relative effects of tree clearing, increased livestock densities and nutrient enrichment have rarely been compared across markedly different organism types, but negative effects are generally predicted. In contrast, adoption of rotational grazing is thought to benefit biodiversity in pastures but there are few supporting data. We examined the response of native plants, birds and reptiles to livestock management in south-eastern Australia. We selected 12 pairs of rotationally and continuously grazed farms. Two 1-ha plots were established in native pastures on each farm, one cleared and the second still retaining woodland tree cover. Stocking rates, fertilizer histories and landscape tree cover varied among farms. The abundance and richness of all taxa was lower in cleared pastures. The less mobile organisms (reptiles and plants) were positively correlated with tree cover at landscape scales, but only when trees were present at the plot scale. This pattern was driven by a few observations in landscapes with approximately 50% tree canopy cover. Neither bird abundance nor richness was correlated with stocking rates or nutrient enrichment, but plant richness responded negatively to both. The response of reptiles varied, declining with nutrient enrichment but positively correlated with livestock densities. These responses may be partly interpreted within the context of prior filtering of species pools through long-term grazing pressure. No taxa responded positively to rotational grazing management. We predict that reductions in livestock density and soil nutrients will directly benefit plants and less so reptiles, but not birds. Indirect benefits are predicted for birds and reptiles if management increases persistence of trees within paddocks. Although some forms of rotational grazing can increase woodland tree recruitment, rotational grazing in itself is unlikely to enhance diversity.
A fundamental part of developing effective biodiversity conservation is to understand what factors affect the distribution and abundance of particular species. However, there is a paucity of data on ecological requirements and habitat relationships for many species, especially for groups such as reptiles. Furthermore, it is not clear whether habitat relationships for particular species in a given environment are transferable to other environments within their geographical range. This has implications for the type of ‘landscape model’ used to guide management decisions in different environments worldwide. To test the hypothesis that species-specific habitat relationships are transferable to other environments, we present microhabitat models for five common lizard species from a poorly studied habitat – insular granite outcrops, and then compared these relationships with studies from other environments in south-eastern Australia. We recorded twelve species from five families, representing 699 individuals, from 44 outcrops in the south-west slopes of New South Wales. Five lizard species were abundant and accounted for 95% of all observations: Egernia striolata, Ctenotus robustus, Cryptoblepharus carnabyi, Morethia boulengeri and Carlia tetradactyla (Scincidae). Linear regression modelling revealed suites of different variables related to the abundance patterns of individual species, some of which were broadly congruent with those measured for each species in other environments. However, additional variables, particular to rocky environments, were found to relate to reptile abundance in this environment. This finding means that species' habitat relationships in one habitat may not be readily transferable to other environments, even those relatively close by. Based on these data, management decisions targeting reptile conservation in agricultural landscapes, which contain rocky outcrops, will be best guided by landscape models that not only recognize gradients in habitat suitability, but are also flexible enough to incorporate intraspecies habitat variability.