Richard H. Loyn

Modelling landscape distributions of large forest owls as applied to managing forests in north-east Victoria, Australia

A landscape approach was taken to modelling distributions of large forest owls and conserving habitat for them in 1.2 million ha of forest on the Great Dividing Range in north-east Victoria, south-eastern Australia. Owls were surveyed using call playback at 472 sites, selected by stratified random sampling from geographical information system (GIS) data. Habitat data were collected at each site and at four spatial scales from GIS data. Six owl species were recorded in or near the study region. Data on powerful owls (Ninox strenua) and sooty owls (Tyto tenebricosa) were modelled using logistic regression, and predicted probabilities of occurrence were mapped using GIS. Mapped variables explained more variation than habitat variables assessed at survey sites. Powerful owls were most likely to be observed at sites with mature dry forest, many live hollow-bearing trees, diverse habitats within 2 km, and not much pure regrowth within 5 km. Sooty owls were most likely to be observed at sites with wetter more senescent forest associated with tree-ferns (Cyathea australis and Dicksonia antarctica), blanket-leaf (Bedfordia arborescens) and silver wattles (Acacia dealbata), diverse habitats within 500 m and much senescent forest within 5 km. The models were field-tested and found to discriminate well between high and low probability sites. Actual records and then models were used to help select 225 protected areas for large owls, each of approximately 500 ha.

Waterbird use of artificial wetlands in an Australian urban landscape

With the loss of natural wetlands, artificial wetlands are becoming increasingly important as habitat for waterbirds. We investigated the relationships between waterbirds and various biophysical parameters on artificial wetlands in an Australian urban valley. The densities (birds per hectare) of several species were correlated (mostly positively) with wetland area, and correlations were observed between certain species and other physical and water chemistry variables. Waterbird community structure, based on both abundance (birds per wetland) and density data, was most consistently positively correlated with the relative amount of wetland perimeter that was vegetated, surface area, distance to nearest wetland, public accessibility and shoreline irregularity. We also compared the relative use of the two types of urban wetlands, namely urban lakes and stormwater treatment wetlands, and found for both abundance and density that the number of individuals and species did not vary significantly between wetland types but that significant differences were observed for particular species and feeding guilds, with no species or guild being more abundant or found in greater density on an urban lake than a stormwater treatment wetland. Designing wetlands to provide a diversity of habitat will benefit most species.

What can a database compiled over 22 years tell us about the use of different types of wetlands by waterfowl in south-eastern Australian summers?

Abstract Understanding the roles of different types of natural and artificial wetlands in providing habitat for waterbirds is crucial to active interventions to conserve wetland biodiversity. This study made use of a large database compiled over 22 years from the ‘Summer Waterfowl Count’ to determine the relative use of five wetland types by 18 species of waterfowl in Victoria, south-eastern Australia. The abundance of 14 species and density of 15 differed significantly (P<0.05) according to wetland type. Waste stabilisation ponds supported significantly higher abundances and densities of many species, a greater number of species and a community structure that was markedly different from the other wetland types. Based on the findings of this study, we believe that the unique characteristics of each wetland type warrant the conservation of each. Moreover, waste stabilisation ponds are significant refugia for waterfowl in Victoria and the trend to modernise sewage treatment plants, to the detriment of waterfowl, should be approached with caution. It is suggested that these findings are probably applicable in other parts of the world, although further research is needed to confirm their universal application.

Associations between salinity and use of non-riverine wetland habitats by diurnal birds

Abstract The secondary salinisation of wetlands is a global problem that poses a profound threat to freshwater biodiversity. We examined wetland use by diurnal birds in relation to wetland salinity in the Wimmera region of southeastern Australia to better understand the threat posed to biodiversity by secondary salinisation. Forty species of birds were detected in 66 non-riverine wetlands that spanned the broad range of salinities encountered among wetlands in the study region. Use of wetlands by birds was related to conductivity of water using a statistical model that accounted for imperfect detection of bird species during the surveys. Of the 40 species encountered during the study, it was estimated that 20 (95% credible interval 17–24) would respond positively to increasing salinity, and 20 (95% credible interval 16–23) would respond negatively to increased salinity. Expected species numbers are highest in wetlands of intermediate salinity. Our results accord well with our existing understanding of wetland use and salinity for most bird species we encountered, and show that expected future increases in wetland salinity are likely to dramatically alter patterns of wetland use by birds.

Quantifying extinction risk and forecasting the number of impending Australian bird and mammal extinctions

A critical step towards reducing the incidence of extinction is to identify and rank the species at highest risk, while implementing protective measures to reduce the risk of extinction to such species. Existing global processes provide a graded categorisation of extinction risk. Here we seek to extend and complement those processes to focus more narrowly on the likelihood of extinction of the most imperilled Australian birds and mammals. We considered an extension of existing IUCN and NatureServe criteria, and used expert elicitation to rank the extinction risk to the most imperilled species, assuming current management. On the basis of these assessments, and using two additional approaches, we estimated the number of extinctions likely to occur in the next 20 years. The estimates of extinction risk derived from our tighter IUCN categorisations, NatureServe assessments and expert elicitation were poorly correlated, with little agreement among methods for which species were most in danger-highlighting the importance of integrating multiple approaches when considering extinction risk. Mapped distributions of the 20 most imperilled birds reveal that most are endemic to islands or occur in southern Australia. The 20 most imperilled mammals occur mostly in northern and central Australia. While there were some differences in the forecasted number of extinctions in the next 20 years among methods, all three approaches predict further species loss. Overall, we estimate that another seven Australian mammals and 10 Australian birds will be extinct by 2038 unless management improves.