Rodney P. Kavanagh

ESTIMATING AND DEALING WITH DETECTABILITY IN OCCUPANCY SURVEYS FOR FOREST OWLS AND ARBOREAL MARSUPIALS

Abstract Surveys that record the presence or absence of fauna are used widely in wildlife management and research. A false absence occurs when an observer fails to record a resident species. There is a growing appreciation of the importance of false absences in wildlife surveys and its influence on impact assessment, monitoring, habitat analyses, and population modeling. Very few studies explicitly quantify the rate of these errors. Quantifying the rate of false absences provides a basis for estimating the survey effort necessary to assert that a species is absent with a pre-specified degree of confidence and allows uncertainty arising from false absences to be incorporated in inference. We estimated the rate of false absences for 2 species of forest owl and 4 species of arboreal marsupial based on 8 repeat visits to 50 survey locations in south-eastern Australia. We obtained estimates using a generalized zero-inflated binomial model. We presented detectability curves for each species to convey the number of visits required to achieve a specified level of confidence that resident species will be detected. The observation error rates we calculated were substantial but varied between species. For the least detectable species, the powerful owl (Ninox strenua), our standard surveys returned false absences on 87% of visits. However, our surveys of the more detectable sugar glider (Petaurus breviceps) returned a 45% false absence rate. We predict that approximately 18 visits would be required to be 90% sure of detecting resident owls and approximately 5 visits would provide 90% confidence of detecting resident sugar gliders. We fitted hierarchical logistic regression models to the data to describe the variation in detection rates explained by environmental variables. We found that temperature, rainfall, and habitat quality influenced the detectability of most species. Consideration of observation error rates could result in important changes to resource management and conservation planning.

Distribution of nocturnal forest birds and mammals in relation to the logging mosaic in south-eastern New South Wales, Australia

Abstract Numbers of nocturnal forest birds and mammals were estimated at 200 widely spaced sites in south-eastern New South Wales to determine their distribution in relation to logging. The focus was on the logged-unlogged forest mosaic rather than on individual logged or unlogged patches. This approach, which compared large areas of unlogged forest with large areas of forest occurring within a logged-unlogged mosaic, was expected to provide more biologically meaningful results, particularly for species with large home ranges. Sampling sites were stratified by geology, within a specified range of mean annual rainfall, and by logging history. Analyses also considered the role of elevation, predominant vegetation community and the proportion of the surrounding landscape which had been logged. All species, with the exception of the greater glider Petauroides volans, were recorded as frequently or more frequently in forests growing on Ordovician sediments. These forests, compared with those on Devonian granites, typically occurred at lower elevations in the region. Multivariate analysis of landscape components suggested that elevation and predominant vegetation community were better predictors of animal occurrence than geology. Logging history appeared to have less influence on counts for most species than geology and/or elevation. The status of many species of nocturnal forest animals is reported in relation to the current logged-unlogged forest mosaic in south-eastern New South Wales. The species having the strongest association with unlogged forest was the greater glider. Numbers of the two largest species of forest owls, the powerful owl Ninox strenua and the sooty owl Tyto tenebricosa, were not disadvantaged at the landscape scale by the current pattern of logging. Our findings indicate the need for maintenance and strengthening of management prescriptions designed to retain and protect unlogged forest in gullies which is recognised as important habitat for most species. Some species, particularly the powerful owl, sooty owl, masked owl Tyto novaehollandiae, greater glider and the yellow-bellied glider Petaurus australis, are likely to require careful management during the second half of the first cutting cycle when adjacent unlogged coupes are cut.

Koalas continue to occupy their previous home-ranges after selective logging in Callitris–Eucalyptus forest

The koala (Phascolarctos cinereus) is a charismatic, high-profile species whose conservation needs are commonly perceived to be incompatible with logging. However, koala biology and the results of chronosequence studies elsewhere suggest that this species may tolerate a degree of habitat alteration caused by logging. In this study, 30 koalas, five in each of six areas available for logging within a mixed white cypress pine (Callitris glaucophylla)–Eucalyptus forest in north-western New South Wales, were radio-tracked for one year during 1997–1998 to determine their movements, home-range sizes and tree preferences. Five months after the study began, three of these areas were logged selectively for sawlogs and thinnings of the white cypress pine, a tree that is important to koalas for daytime shelter. This removed about one-quarter of the stand basal area, but the eucalypt component was unaffected. The remaining three areas were left undisturbed as controls. Radio-tracking continued in all six areas for another seven months. Koalas continued to occupy all or part of their previous home-ranges after selective logging, and home-range sizes remained similar between logged and unlogged areas. Home-ranges for both sexes overlapped and were ~12 ha for males and 9 ha for females. Koala survival and the proportions of breeding females were similar in logged and unlogged areas. The principal food trees of the koala were red gums, mainly Eucalyptus blakelyi and E. chloroclada, and the pilliga box (E. pilligaensis), none of which were logged in this study. These results suggest that selective logging for white cypress pine does not appear to adversely affect koala populations and that koalas may not be as sensitive to logging as previously thought. Further work is required to determine thresholds in the level of retention of koala food trees in logging operations.

Detecting pest and prey responses to fox control across the landscape using remote cameras

Context The red fox (Vulpes vulpes) is a widespread pest in southern Australia and is subject to control over large areas using poison baits to protect both agricultural and ecological assets. Foxes and their prey are often cryptic or in low densities, making it difficult to quantify the efficacy of control programs. Aims We explore the use of remote cameras to estimate the activity and spatial occupancy of foxes and potential mammalian and avian prey species before and after poison baiting in the Goonoo region, central New South Wales. Methods In the first of two studies, we set camera traps at 48 sites in forest and cleared areas, on and off tracks, during autumn 2009. In the second study, we placed camera traps in forest and cleared areas, on tracks only, at 100 sites covering an area of ~441 500 ha during winter 2009. We examined camera-trap rates of all species detected and the activity and site occupancy of a selected subset of species before and after poison baiting. Key results Camera traps indicated greater levels of fox activity on vehicular tracks than off them, with this difference being more marked in forest than in cleared agricultural land. Fox activity and occupancy were greater in agricultural land than in forest, with no effect of baiting detected at the landscape scale. Thirty-five other mammal and bird species were identified from photos, with activity for most being greater on than off tracks. Conclusions No clear effects of fox-baiting were detected on foxes or potential prey species in either study by either activity or occupancy. The lack of a baiting effect may reflect rapid recolonisation by foxes from unbaited areas, as bait placement is generally clustered in agricultural land, or the ready availability of alternative food (lambs or lamb carcasses) in some cleared areas. Implications Our results demonstrate that remote cameras provide a simple means of monitoring changes in fox activity and occupancy at the landscape level, and that these measures have great potential to quantify the success or otherwise of fox-control campaigns on both pest and prey species.

Bird population recovery 22 years after intensive logging near Eden, New South Wales

Abstract Intensive logging for sawlogs and woodchips in south-eastern Australia is known to cause an immediate impact on bird populations. We measured bird abundance and species turnover during the medium term (13 and 22 years) after intensive alternate-coupe logging in a forest area that had been studied previously for short-term (0–4 years) impacts. The study provides a series of snapshots of bird population recovery following one of the most intensive logging operations in the region when, unlike the current practice, no old trees were retained in logged areas and no unlogged forest was retained in strips along all drainage lines. The aim was to assess the longer-term effects of logging on the bird assemblage and to determine whether recovery had occurred. We found that recovery had occurred for a large component of the avifauna within 22 years of intensive logging (as practised in 1976 when few or no old trees were retained in logged areas). Most bird species that forage among canopy foliage, in the air, among the understorey and on the ground had recovered. Five common forest birds were significantly more common on logged coupes than unlogged coupes. The Bell Miner, Manorina melanophrys, a honeyeater often associated with disturbed forest and implicated in eucalypt canopy dieback, had established colonies on some logged coupes 22 years after intensive logging. However, some hollow-nesting bird species (e.g. treecreepers, cockatoos) had still not fully recovered. A number of other common forest birds occurred so rarely in the study area (on both logged and unlogged coupes) that few conclusions could be made about their responses to logging. Evidence suggested that intensive logging may have had an effect at a local landscape (compartment) level as well as at the level of individual logged coupes. This was indicated by changes to the avifauna of the unlogged coupes over time (increasing numbers of species) as the forest regenerated on the adjacent logged coupes.

Nocturnal forest birds and arboreal marsupials of the southwestern slopes, New South Wales

A regional survey of 253 forest sites on the southwestern slopes and adjacent highlands of New South Wales recorded a total of 530 animals from five species of nocturnal forest birds and nine species of arboreal marsupials. One additional species, the Squirrel Glider Petaurus norfoicensis, was tapped during supplementary searches. Elevation (climate) and best type were the major factors accounting for the distribution of this fauna. Minor environmental gradients included geology, the density of hollow-bearing trees, topography, logging intensity and fire. The patterns of landuse in the region contributed to interactions between elevation, forest type and management history (logging, fire and grazing) which restricted inferences about the habitat requirements of animals.Forest types occurring at either end of the elevational (wet-dry) gradient (Alpine Ash and Box-Stringybark) were poorer in species than forests occurring at intermediate elevations (Alpine Gums, Wet Peppermint and Dry Peppermint). The Wet P...

Mapping forest patches and scattered trees from SPOT images and testing their ecological importance for woodland birds in a fragmented agricultural landscape

Scattered trees represent an important element within the agricultural matrix for birds. The aims of this study were to develop methods for mapping isolated trees from satellite imagery and to assess the importance of isolated trees for bird species richness. Field sampling of birds and plants was conducted at 120 sites in south-east Australia. We mapped tree cover from Landsat and SPOT images using a combination of spectral and segmentation based methods. Mapping of isolated trees as point objects was highly accurate (80–90%). Tree cover at spatial extents of 3–28 ha around sites explained 60% of the variability in woodland–dependent bird species richness. However, isolated trees in agricultural areas made just a small contribution to explaining the spatial variability in overall avian richness. This approach can be used for more extensive assessment of avian habitat quality from high spatial resolution images across a range of human modified landscapes.

Quantifying successional changes in response to forest disturbances

ABSTRACT Question: Can dissimilarity measures of individual plots be used to forecast the driving factors among various anthropogenic disturbances influencing understorey successional changes? Location: Yambulla State Forest, south-eastern Australia (37°14′ S, 149°38′ E). Methods: Assessments of understorey vegetation communities were taken prior to anthropogenic disturbances and at three subsequent time periods representing a period of 15 years post-disturbance. Dissimilarities were calculated from the original assessment and modelled in a Bayesian framework to examine the influence of logging, number of prescribed burns and time. Results: All sites underwent significant changes over time independently of the imposed management regimes. Logging resulted in an immediate change in vegetation assemblage which decreased in the subsequent assessments. The number of prescribed fires brought greater change in the shrub vegetation assemblages, but less change in the ground species vegetation assemblages. Conclusions: The anthropogenic disturbances did have some role in the changes of vegetation assemblages but these were minimal. The ongoing changes appear to be a natural response to the last wildfire, which passed through the study area in 1973 (13 years prior to the study). Forest management practices should consider the influence of wildfire succession when planning for the conservation of biodiversity.

Patch-Occupancy Modeling as a Method for Monitoring Changes in Forest Floristics: a Case Study in Southeastern Australia

The ability to monitor changes in biodiversity is fundamental to demonstrating sustainable management practices of natural resources. Disturbance studies generally focus on responses at the plot scale, whereas landscape-scale responses are directly relevant to the development of sustainable forest management. Modeling changes in occupancy is one way to monitor landscape-scale responses. We used understory vegetation data collected over 16 years from a long-term study site in southeastern Australia. The site was subject to timber harvesting and frequent prescribed burning. We used occupancy models to examine the impacts of these disturbances on the distribution of 50 species of plants during the study. Timber harvesting influenced the distribution of 9 species, but these effects of harvesting were generally lost within 14 years. Repeated prescribed fire affected 22 species, but the heterogeneity of the burns reduced the predicted negative effects. Twenty-two species decreased over time independent of treatment, and only 5 species increased over time. These changes probably represent a natural response to a wildfire that occurred in 1973, 13 years before the study began. Occupancy modeling is a useful and flexible technique for analyzing monitoring data and it may also be suitable for inclusion within an adaptive-management framework for forest management.

Balancing trade-offs between biodiversity and production in the re-design of rangeland landscapes

The conflict that exists between the competing needs of biological conservation and pastoral production is well recognised but few studies have examined these conflicts due to their complexity and the uncertainty that surrounds these relationships. The development of a Bayesian network model that examines the trade-offs between the conservation value of the landscape for a range of taxa (flora, mammals, birds and herpetofauna) and its primary production value under alternative land uses is described. The model emphasises structural diversity of vegetation and ecosystem productivity as key drivers of both biodiversity and agricultural production. Simple scenarios, used to examine the influence of different land uses on multiple components of biodiversity and agricultural productivity, demonstrated the potential for the analysis of the trade-offs associated with alternative landscape designs. The potential of the model, as a planning or policy development tool for land management agencies or regional Natural Resource Management bodies, at multiple scales, is identified.