Testing the importance of spatial configuration of winter habitat for woodland caribou: An application of graph theory

Conservation of remaining woodland caribou (Rangifer tarandus caribou) populations requires land management strategies that not only maintain caribou habitat, but also favour habitat connectivity. This study presents and field tests graph theory-based measures of landscape connectivity, and demonstrate an association between the distribution of woodland caribou and well-connected winter habitat. Cost values for the intervening land cover types were determined based on the probability of selection relative to high-quality winter habitat. Habitat connectivity was then represented by linking high-quality habitat patches along least-cost paths through this parameterized cost surface. A randomization procedure was used to assess the animal’s association with habitat connected at increasing distance thresholds to identify appropriate scales of response. A strong relationship was obtained between large clusters of high-quality winter habitat patches and winter GPS telemetry location points (November 1-March 15) from two woodland caribou herds in Manitoba, Canada. This relationship was stronger when only late winter location points (January 1-March 15) were used. Our results highlight the importance of accounting for the spatial configuration of habitat on the landscape and the intervening land cover types when assessing range quality for woodland caribou. They also provide support for the use of graph theory to assist in identifying core activity areas for woodland caribou and key linkages between these areas and other parts of the landscape.     

Gap-crossing by gliding marsupials: thresholds for use of isolated woodland patches in an agricultural landscape

Single trees and small patches of trees in farmland are conspicuous components of agricultural landscapes around the world, but their value for the conservation of biodiversity is not well known. In this study, arboreal mammals were censused by using hair-sampling tubes in small patches of woodland (single trees to patches <1.0 ha) in cleared farmland adjacent to a linear network of woodland known to support resident populations of arboreal mammals. Ninety-one small isolates were stratified by size (single trees or small patches) and distance from the linear network to test the capacity of animals to cross habitat ‘gaps’. The genus Petaurus (small gliding marsupials), the most commonly detected taxon, was recorded in 31% of hair-tubes (98 of 316). It occurred in 21% of sites in isolated trees and patches, and in all linear strips. A logistic regression model demonstrated that Petaurus sp. was most likely to occur in isolates in close proximity to linear strips and other patches of woodland. Ninety-five per cent of sites at which this taxon occurred were within 75 m of the linear network. This threshold corresponds with the maximum distance that animals can glide in a single movement between trees. The size of isolates did not influence utilisation rates. Such isolates are smaller than a single home range and were probably used to supplement home ranges centred on the linear network, by providing additional foraging habitat and den sites. Protection and restoration of isolated trees and small woodland clumps in cleared landscapes contributes to mammal conservation and this study provides quantitative data that can assist landscape design and habitat restoration in rural environments.     

Range fidelity: The missing link between caribou decline and habitat alteration?

Conservation of forest-dwelling caribou (Rangifer tarandus caribou) is of great concern across most of its range. Anthropogenic disturbances, primarily logging activities, have been identified as the most important cause of caribou decline, although the mechanisms underlying this decline are not fully understood. Caribou commonly display fidelity to calving sites or seasonal ranges, but the potential role of this life-history trait has been largely overlooked in research and conservation planning. This is surprising because sites and ranges with high inter-annual use should have high conservation value. We investigated the relationship between habitat disturbances and home-range fidelity of forest-dwelling caribou across three study sites in Québec, Canada, using a broad range of natural and anthropogenic disturbances. Between 2004 and 2007, we tracked 47 adult female caribou using GPS collars. Home-range fidelity varied between seasons, being higher during calving and summer, and lower during winter. Caribou reduced fidelity following natural and anthropogenic disturbances, the latter having a stronger negative influence. Anthropogenic disturbances had a strong negative impact on home-range fidelity during annual, summer and winter periods, whereas natural disturbance was the dominant factor during calving. Despite this negative influence on fidelity, caribou tended to demonstrate range fidelity even in study sites most impacted by human activities. Habitat disturbances could produce two possible outcomes for caribou conservation: (1) a trend for females to reduce home-range fidelity which could translate into lower calf and female caribou survival through reduced familiarity with food distribution, escape cover and predation risk and (2) a global tendency to maintain range fidelity even in a drastically modified landscape which could turn into an ecological trap, particularly for calves when predation risk increases due to increased black bear density in early successional forests. Taking range fidelity behavior into consideration during forest management planning could direct conservation efforts toward the best available sites and therefore facilitate caribou persistence in managed landscapes.     

Assessing critical habitat: Evaluating the relative contribution of habitats to population persistence

A principal challenge of species conservation is to identify the specific habitats that are essential for long-term persistence or recovery of imperiled species. However, many commonly used approaches to identify important habitats do not provide direct insight into the contribution of those habitats to population persistence. To assess how habitats contribute to overall population viability and characterize their relative importance, a spatially-explicit population viability model was used to integrate a species occurrence model with habitat quality and demographic information to simulate the population dynamics of the Ord’s kangaroo rat (Dipodomys ordii) in Alberta, Canada. Long-term productivity (births-deaths) in each patch was simulated and iterative patch removal experiments were conducted to generate estimates of the relative contribution of habitat types to overall population viability. Our results indicated that natural dune habitats are crucial for population viability, while disturbed/human-created habitats make a minor contribution to population persistence. The results also suggest that the habitats currently available to Ord’s kangaroo rats in Alberta are unlikely to support long-term persistence. Our approach was useful for identifying habitats that did not contribute to population viability. A large proportion of habitat (39%) represented sinks and their removal increased estimated population viability. The integration of population dynamics with habitat quality and occurrence data can be invaluable when assessing critical habitat, particularly in regions with variable habitat quality. Approaches that do not incorporate population dynamics may undermine conservation efforts by under- or over-estimating the value of habitats, erroneously protecting sink habitats, or failing to prioritize key source habitats.     

Factors influencing the dispersion and fragmentation of endangered mountain caribou populations

Mountain caribou, an ecotype of woodland caribou, are endangered due to the loss and fragmentation of old forests on which they depend. However, a wider array of natural and human factors may limit caribou persistence and isolate populations, and understanding these may help to stop or reverse population declines by forecasting risk and targeting core habitat areas and key linkages for protection, enhancement or restoration. Across most of the historic range of mountain caribou, we conducted a bi-level analysis to evaluate factors related to the persistence of, and landscape occupancy within, remaining subpopulations. We used caribou location data from 235 radio-collared animals across 13 subpopulations to derive a landscape occupancy index, while accounting for inherent sampling biases. We analyzed this index against 33 landscape variables of forest overstory, land cover, terrain, climate, and human influence. At the metapopulation level, the persistence of subpopulations relative to historic range was explained by the extent of wet and very wet climatic conditions, the distribution of both old (>140 yr) forests, particularly of cedar and hemlock composition, and alpine areas. Other important factors were remoteness from human presence, low road density, and little motorized access. At the subpopulation level, the relative intensity of caribou landscape occupancy within subpopulation bounds was explained by the distribution of old cedar/hemlock and spruce/subalpine fir forests and the lack of deciduous forests. Other factors impeding population contiguity were icefields, non-forested alpine, hydro reservoirs, extensive road networks, and primary highway routes. Model outputs at both levels were combined to predict the potential for mountain caribou population persistence, isolation, and restoration. We combined this output with the original occupancy index to gauge the potential vulnerability of caribou to extirpation within landscapes known to have recently supported animals. We discuss implications as they pertain to range-wide caribou population connectivity and conservation.     

Variation in wolf spider (Araneae: Lycosidae) distribution and abundance in response to the size and shape of woodland fragments

The wolf spider (Lycosidae) community of open paddocks and five different configurations of woodland habitat in the wheatbelt of New South Wales, Australia, was sampled by nocturnal spotlighting. A total of 16 species was detected amongst the 2769 individuals that were sufficiently mature to allow identification, and 80% of these individuals were accounted for by just three species. There were no significant differences in the spider community among any of the woodland configurations, but the community of all five configurations differed significantly from that of open paddocks. However, only three species differed significantly in abundance between paddocks and the woodland configurations. Two species, Venator spenceri and Sp. C appeared to be less common in paddocks than in the woodland habitats, while Sp. A was more abundant in the paddocks. The percentage cover of thistles, medium grass and high grass, as well as the total abundance of Callitris glaucophylla were the habitat variables that best explained variation in the wolf spider community between woodland sites. Of these, thistle cover had the strongest correlation suggesting that disturbance, rather than cover per se, might be an important determinant of wolf spider communities. This study indicates that habitat fragmentation, at the spatial scale associated with current agricultural practices, may not be presenting a threat to generalist ground predators such as wolf spiders.     

The habitat requirements of the rufous treecreeper (Climacteris rufa). 1. Preferential habitat use demonstrated at multiple spatial scales

Determining the habitat requirements of a species is fundamental to effective conservation, particularly if the species is declining in areas where its habitat is being modified. Multi-scaled investigations of habitat use are essential because different selection processes may operate at different scales. I examined the habitat use of a declining woodland passerine, the rufous treecreeper (Climacteris rufa), at three spatial scales (landscape, woodland and territory) in the wheatbelt of Western Australia. Preferential habitat use was exhibited at all scales. At the landscape scale, wandoo (Eucalyptus wandoo) woodland was used at a significantly greater rate than three other common vegetation types. Territory use within woodlands was positively related to the density of hollow-bearing logs, the density of nest sites, and tree age. Within an individual territory, nest sites (hollows) were favoured if they had a spout angle of ?50° to the horizontal and an entrance size of between 5 and 10 cm. The rufous treecreeper preferentially used habitat with traits characteristic of old-growth wandoo woodland. Degradation of wandoo through habitat modification (e.g. grazing, logging, fire and removal of deadwood) represents a significant threat to the persistence of treecreepers.     

生态修复措施对干旱半干旱地区生态系统服务影响研究——以河北坝上地区为例

为了揭示生态修复措施对干旱半干旱地区生态系统服务的影响,以对生态可持续发展提供决策参考,基于典型的干旱半干旱地区——河北坝上地区2000年、2018年土地利用数据以及4种与生态修复措施对应的情景,结合InVEST模型分析了生态修复措施对该区3个重要的生态系统服务(水源涵养、生境质量、碳储量)的影响。结果显示:(1) 2000—2018年坝上地区土地利用变化以草地大量缩减以及林地显著扩张为主(>500 km²),期间,水源涵养量下降7.03%,碳储量、生境质量分别增长2.82%,1.29%;(2)相比林地缓冲带、植树造林情景,开垦荒地和综合发展情景对上述3个生态系统服务的提高更为显著;(3)水源涵养、碳储量均与生境质量呈较强协同作用(r>0.42),碳储量与水源涵养呈较弱协同作用(r<0.24)。综上分析,生态修复措施能够提高坝上地区生态系统服务的供给,但以造林为主的生态修复方式在干旱半干旱地区仍需谨慎实施。     

Identifying indirect habitat loss and avoidance of human infrastructure by northern mountain woodland caribou

Understanding the impact of indirect habitat loss resulting from avoidance of human infrastructure is an important conservation priority. We evaluated resource selection for 10 global positioning system collared northern mountain woodland caribou (Rangifer tarandus caribou) in British Columbia, Canada, with seasonal resource selection functions (RSF) developed at the second-order (landscape) and third-order (within home range) scales. To estimate how much habitat was lost due to avoidance, we estimated the zone of influence (ZOI) around multiple developments and modeled realized and potential habitat. Potential habitat was approximated by removing the ZOI from RSF models. By calculating the spatial difference between potential and realized habitat we estimated the amount of indirect habitat loss. Caribou displayed hierarchical avoidance of development, with the greatest avoidance occurring at the second-order. During both seasons caribou avoided high-use roads by 2 km and low-use roads by 1 km. In winter, caribou avoided town by 9 km compared to 3 km in summer. However, in summer caribou avoided mines by 2 km and cabins and camps by 1.5 km, while in winter when human activity was low, avoidance of these features was minor. As a result of avoidance of the cumulative ZOI, approximately 8% and 2% of high quality habitat was lost in the study area in winter and summer, respectively. Our study provides an approach to identify the extent and quality of habitat influenced by indirect avoidance. Conservation efforts should prioritize protecting areas of high quality habitat degraded by avoidance in the vicinity of human development.     

Farmer attitudes toward wolves: Implications for the role of predators in managing disease

The potential for disease transmission between wild and domestic animals may interfere with wildlife and habitat conservation on lands surrounding protected areas. Recently, possible transmission of bovine tuberculosis (Mycobacterium bovis) from wild ungulates to domestic livestock has affected the Riding Mountain National Park region in Manitoba, Canada. Wolf (Canis lupus) predation on ungulate populations may help lessen the risk of disease transmission to livestock. We conducted an exploratory analysis of causal factors associated with farmer attitudes toward observing wolves on their farms. A survey to 4 220 farms within 50 km of the Park resulted in an adjusted response rate of 25%. We constructed several logistic regression models with factors hypothesized to influence whether farmers agreed with the statement “I enjoy seeing wolves on my land”, and three candidate models received reasonable support. Factors most affecting attitudes were, in order of importance, perceived wolf population size, frequency of seeing wolves, perceived seriousness of wolf damage, distance to Park boundary and number of beef cattle (Bos taurus) owned. The factors least influential on attitudes were education and age. Concern over bovine tuberculosis in wild elk also had minimal influence. Of respondents who perceived the wolf population as “too high”, 60% were extremely concerned about bovine tuberculosis in wild elk. Although the role of wolf predation as a potential natural regulator of disease in wild ungulates might not be widely recognized in many areas, we believe this provides a unique opportunity to re-examine the significance of maintaining viable wolf populations.     

European Bison habitat in the Carpathian Mountains

European Bison (Bison bonasus) barely escaped extinction in the early 20th century and now only occur in small isolated herds scattered across Central and Eastern Europe. The species’ survival in the wild depends on identifying suitable habitat for establishing bison metapopulations via reintroductions of new herds. We assessed European Bison habitat across the Carpathian Mountains, a stronghold of European Bison and one of the only places where a viable bison metapopulation may be possible. We used maximum entropy models to analyze herd range maps and habitat use data from radio-collared bison to identify key habitat variables and map European Bison habitat across the entire Carpathian ecoregion (210,000 km²). Forest cover (primarily core and perforated forests) and variables linked to human disturbance best predict bison habitat suitability. Bison show no clear preference for particular forest types but prefer managed grasslands over fallow and abandoned fields. Several large, suitable, but currently unoccupied habitat patches exist, particularly in the eastern Carpathians. This available suitable habitat suggests that European Bison have an opportunity to establish a viable Carpathian metapopulation, especially if recent trends of declining human pressure and reforestation of abandoned farmland continue. Our results also confirm the suitability of a proposed Romanian reintroduction site. Establishing the first European Bison metapopulation would be a milestone in efforts to conserve this species in the wild and demonstrate a significant and hopeful step towards conserving large grazers and their ecological roles in human-dominated landscapes across the globe.     

Thresholds in landscape parameters: occurrence of the white-browed treecreeper Climacteris affinis in Victoria, Australia

The concept of critical thresholds of habitat loss has recently received considerable attention in conservation biology and landscape ecology, yet empirical examples of thresholds are scarce. Threatened species management could benefit from recognition of thresholds because conditions under which populations are at risk can be specified. In this study, 56 woodland patches in north-west Victoria were surveyed for the white-browed treecreeper Climacteris affinis, a threatened insectivorous bird of the semi-arid zone of southern Australia. Comparisons with historic records indicate the species’ range is contracting in Victoria. Using logistic regression and hierarchical partitioning, two models of patch occupancy were developed. Tree species composition was an important factor in both models, confirming the treecreepers’ affinity for belah Casuarina pauper and slender cypress-pine Callitris gracilis-buloke Allocasuarina luehmannii woodlands in north-west Victoria. The first model emphasized the importance of demographic isolation: probability of patch occupancy decreased with distance to the nearest occupied patch. A threshold response in demographic isolation was apparent. In agricultural landscapes, most suitable woodland patches within 3 km of an occupied patch were occupied, whereas patches beyond the threshold were vacant. The threshold distance increased to a minimum of 8 km in a matrix of native vegetation, suggesting landscape context affects the response of white-browed treecreepers to habitat fragmentation. Demographic isolation is a quasi-dependent variable and therefore a second model was developed using surrogate variables for demographic isolation. A positive relationship with the proportion of woodland cover in the landscape (100 km²) emerged as the pre-eminent explanatory factor. Depending on woodland quality, a threshold of patch occupancy was apparent at levels of woodland cover between 15 and 25%. However, belah and slender cypress-pine-buloke woodlands now cover only 10% of their original extent in the region. These results highlight the inter-dependence of patch isolation with the amount and quality of habitat in the landscape and the implications this has for maintaining functional connectivity. The retention (or restoration) of suitable habitat is the critical issue for conservation of the white-browed treecreeper, but in landscapes below the threshold of habitat cover, viability of local populations may be influenced by the configuration and quality of remaining habitat.     

Factors and scales potentially important for saproxylic beetles in temperate mixed oak forest

The influence of environmental factors on species richness and species composition may be manifested at different spatial levels. Exploring these relationships is important to understand at which spatial scales certain species and organism groups become sensitive to fragmentation and changes in habitat quality. At different spatial scales we evaluated the potential influence of 45 factors (multiple regression, PCA) on saproxylic oak beetles in 21 smaller broadleaved Swedish forests of conservation importance (woodland key habitats, WKH). Local amount of dead wood in forests is often assumed to be important, but two landscape variables, area of oak dominated woodland key habitats within 1 km of sites and regional amount of dead oak wood, were the main (and strong) predictors of variation in local species richness of oak beetles. The result was similar for red-listed beetles associated with oak. Species composition of the beetles was also best predicted by area of oak woodland key habitat within 1 km, with canopy closure as the second predictor. Despite suitable local quality of the woodland key habitats, the density of such habitat patches may in many areas be too low for long-term protection of saproxylic beetles associated with broadleaved temperate forests. Landscapes with many clustered woodland key habitats rich in oak should have high priority for conservation of saproxylic oak beetles.     

Area use by white-lipped and collared peccaries (Tayassu pecari and Tayassu tajacu) in a tropical forest fragment

We present the first long-term radio telemetry study of area use by white-lipped and collared peccaries in a tropical forest fragment. Population densities of both species in a 2178-ha fragment of semideciduous Atlantic forest in southeastern Brazil were similar to estimates from another regional fragment with 16 times the area. The population of 150 (±52) white-lipped peccaries was divided among 3-4 subherds. We observed a high frequency of switching of individuals among subherds and documented periodic subherd fusion. Seven to 22 collared peccary herds (mean herd size, 9) persisted in the main forest fragment. Average home range size for the white-lipped peccaries was 1871 ha (90% HM). This was similar to the few reliable estimates available from continuous tropical forests. Despite supposed area restrictions, white-lipped peccaries maintained distinct seasonal ranges with a minimum of overlap. Within seasons, subherds overlapped spatially, but were separated temporally. Average home range sizes of two radio-tracked collared peccary herds were 305 and 123 ha. Home range boundaries and seasonal ranges of collared peccary herds shifted minimally, and herd subgrouping was short-lived. Spatial overlap between the two peccary species varied seasonally with white-lipped herd movements. We discuss future research needs and management actions for conservation of these species in fragmented landscapes.     

Potential habitat connectivity of European bison (Bison bonasus) in the Carpathians

Habitat connectivity is important for the survival of species that occupy habitat patches too small to sustain an isolated population. A prominent example of such a species is the European bison (Bison bonasus), occurring only in small, isolated herds, and whose survival will depend on establishing larger, well-connected populations. Our goal here was to assess habitat connectivity of European bison in the Carpathians. We used an existing bison habitat suitability map and data on dispersal barriers to derive cost surfaces, representing the ability of bison to move across the landscape, and to delineate potential connections (as least-cost paths) between currently occupied and potential habitat patches. Graph theory tools were then employed to evaluate the connectivity of all potential habitat patches and their relative importance in the network. Our analysis showed that existing bison herds in Ukraine are isolated. However, we identified several groups of well-connected habitat patches in the Carpathians which could host a large population of European bison. Our analysis also located important dispersal corridors connecting existing herds, and several promising locations for future reintroductions (especially in the Eastern Carpathians) that should have a high priority for conservation efforts. In general, our approach indicates the most important elements within a landscape mosaic for providing and maintaining the overall connectivity of different habitat networks and thus offers a robust and powerful tool for conservation planning.     

The age and amount of regrowth forest in fragmented brigalow landscapes are both important for woodland dependent birds

In highly-modified agricultural landscapes, regrowth (secondary) forest on abandoned farmland offers the potential for passive landscape restoration for biodiversity conservation. While numerous studies have investigated the ecological values of regrowth for fauna recovery at the local-level (1-10 ha), there is a dearth of studies quantifying the contribution of regrowth forest at the landscape-level (100-1000s ha). To address this critical knowledge gap we question how the age and amount of regrowth forest in the landscape influence species richness and abundance of mature forest dependent species? Using woodland dependent birds in fragmented sub-tropical brigalow landscapes in southern Queensland, Australia, we applied model averaging and hierarchical partitioning analyses to test and rank the relative importance of the amount of regrowth forest in the landscape in three age classes (<15, 15-30, and >30 years) compared to local (grazing disturbance, abundance of aggressive miners, mistletoe abundance and patch age) and landscape measures of habitat (amount of mature forest and number of mature forest patches). Response variables included the species richness of woodland dependent birds and sub-groupings of foraging guilds, and the abundance of selected individual species. The importance of explanatory variables differed considerably among response groups. Local attributes, such as patch age and the abundance of mistletoe plants, had the strongest influences on woodland dependent birds. However, we found that the amount of regrowth forest, particularly >30 years, also had a strong influence on both species richness and abundance. This study confirms that regrowth, especially older regrowth, can make an important contribution to landscape restoration in highly-modified agricultural landscapes.     

Regional conservation priorities for a large predator: golden eagles (Aquila chrysaetos) in the Alpine range

We compared the density of golden eagles (Aquila chrysaetos) and their nest dispersion, productivity and diet in Alpine and pre-Alpine areas. The comparison was made at two spatial scales: (1) at the territory level within two contiguous populations, and (2) at the population level, using published data for 22 populations scattered across four countries (France, Switzerland, Germany and Italy). Availability of golden eagle's main prey species was higher in Alpine than in pre-Alpine regions. The potential foraging ranges of pairs of eagles in the pre-Alps had larger amounts of woodland and lower amounts of suitable foraging habitat than those of Alpine pairs. At both spatial scales, density and productivity were lower in the pre-Alps. Also, pre-Alpine populations were characterised by a lower percentage of main prey species in the diet, which was significantly correlated with productivity, and by a higher breadth of diet, which was negatively correlated with density. Overall, higher prey availability and habitat suitability in the Alps resulted in higher density and breeding success, in a manner compatible with theoretical metapopulation models. We suggest that priority be given to conservation of eagle populations in high quality Alpine habitat, and that conservation action be carried out by a mixture of site-protection measures and conservation of the wider environment.     

Habitat selection by the Mediterranean horseshoe bat, Rhinolophus euryale (Chiroptera: Rhinolophidae) in a rural area of southern Italy and implications for conservation

We studied habitat selection by Rhinolophus euryale in a rural area of southern Italy in 1998-2000 by radio-tracking. Two comparisons were carried out, one between habitat occurrence within individual home ranges and within the study area, the other between time spent in each foraging habitat and habitat occurrence within the home range. The first analysis showed that olive groves and conifer plantations were, respectively, the most and the least important habitats. The second analysis highlighted the importance of woodland for R. euryale, while urban sites, open areas and conifer plantations were avoided. We recommend that clearing of continuous, large areas of woodland for tree harvesting should be avoided. Conifers should not be used for reforestation. Urbanisation should be limited in the areas of greatest importance for the species, and linear landscape elements such as tree lines and hedgerows should be maintained.     

Human attitudes towards wolves, a matter of distance

The objective of this study was to test the hypothesis that distance is an important factor affecting attitudes towards wolves, i.e. people living far from wolf territories have more positive attitudes towards wolf conservation than those living within or close to wolf territories. We used multiple regression (an ordered probit model) with both socio-economic variables and information about the respondents’ distance to the nearest wolf territory. We found that favourable attitudes towards wolf conservation were positively associated with distance to the nearest wolf territory. The variable distance to the nearest wolf territory affected attitudes just as much as the variables of membership of nature conservation organisations, being a hunter, owning livestock, or owning a hunting dog. This was true even on the micro-level, i.e. people living in wolf territories had a more negative attitude towards conservation of wolves than people living just outside. Furthermore, we suggest that attitudes towards wolves are more likely a result of indirect experience than direct experience of wolf presence. Our findings are important when interpreting studies of human attitudes towards conservation of controversial species in general and large carnivores in particular, and should be used when designing future surveys of human attitudes towards conservation and management initiatives.     

Threshold effect of eucalypt density on an aggressive avian competitor

General guidelines available to revegetation planners focus on the spatial context and dimensions of the revegetated site. However, site-specific habitat factors can have overarching importance for habitat value, especially where interactions with competitors or predators may play an important role. Current revegetation projects in Australia which aim to restore slow-growing buloke (Allocasuarina luehmannii) woodland, a threatened habitat important for bird conservation, usually include faster-growing eucalypts in plantings. This research aimed to identify whether eucalypt presence in buloke woodland facilitates invasion by the noisy miner (Manorina melanocephala), an aggressive competitor that is absent from pure buloke woodland. Birds were surveyed in buloke woodland remnants that contained eucalypts as a sub-dominant species at densities of 0-16 per ha. The probability of noisy miner presence in buloke woodland increased markedly where eucalypts were present at a density of approximately five per hectare. The presence of noisy miners resulted in a substantial difference in bird assemblage structure and composition. Small-bodied insectivorous birds which are experiencing population declines in southern Australia were recorded on average six times more often in transects without noisy miners (low-eucalypt density transects). Avian behaviour and habitat use was also altered, with birds flying more frequently in transects where noisy miners were present. A minor difference in habitat composition results in substantial degradation of the conservation value of non-eucalypt woodland in eastern Australia due to invasion by aggressive avian competitors. Revegetation and restoration practices should take into account the potential for such subtle floristic differences to result in substantial variation in conservation outcomes.