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Koch A.J.,Tasmanian Forest Practices Authority | Koch A.J.,University of Tasmania | Koch A.J.,Cooperative Research Center for Greenhouse Gas Technologies | Baker S.C.,Forestry Tasmania | And 2 more authors.
Biodiversity and Conservation | Year: 2011

Tree hollows provide critical habitat for many species worldwide. The conservation of hollow-bearing trees presents a particular challenge for forest managers, partly due to difficulties in predicting their occurrence across a landscape. We trialled a novel approach for assessing relative hollow availability, by remotely estimating mature crown cover and senescence from aerial photographs in Tasmania, Australia. These estimates were tested against plot-based field assessments of actual occurrence of hollow-bearing trees. In dry forest we conducted ground-based surveys of hollows for all mature trees (>50 cm dbh) in 37 half-hectare plots. In wet forest, we conducted helicopter-based surveys of hollows for all mature trees in 45 oldgrowth plots (0. 29-4. 63 ha). Aerial photographs (1:10,000-1:25,000) were used to classify the senescence and cover of mature crowns in each plot. Regression analysis showed that, in dry forest, hollow-bearing tree densities were strongly related to the remote assessment of mature crown cover, with an 8% increase in variability explained if senescence was also included (R2 = 0. 50). In wet forest, mature crown cover alone was the best model (R2 = 0. 53 when outliers were removed). Assessing senescence was less important in dense wet forests than dry forest because trees take longer to form mature-shaped crowns and so mature-shaped crowns are more likely to have hollows. These results suggest that, with skilled photo-interpretation, aerial photographs can be useful for remotely assessing the relative density of hollow-bearing trees. This approach has the potential to greatly improve conservation planning for hollows and hollow-dependent fauna. © 2011 Springer Science+Business Media B.V. Source


Wiersma J.,Tasmanian Forest Practices Authority | Wiersma J.,Cooperative Research Center for Greenhouse Gas Technologies | Koch A.J.,Tasmanian Forest Practices Authority | Koch A.J.,Cooperative Research Center for Greenhouse Gas Technologies | Koch A.J.,University of Tasmania
Corella | Year: 2012

A standardised protocol for surveying raptor breeding activity based on nest characteristics rather than observations of adults and chicks could reduce the cost and time required for surveys, increase sampling capacity and minimize disturbance to birds. We examined whether the breeding activity of the Tasmanian Wedge-tailed Eagle Aquila audax fleayi can be assessed indirectly by surveying nest characteristics in the late stages of breeding or after the breeding season. The presence or absence of nestlings (approximately 4-6 weeks old) in 75 nests was assessed either from the air or from the ground during the 2007-2008 breeding season. Two sources of data on nest characteristics were available and were considered separately. One set (37 nests) was collected after the breeding season by eagle biologists during aerial (helicopter) or ground-based surveys. The other set (38 nests) was collected during the breeding season, by trained forest planners during ground-based surveys. A high proportion of the nests containing nestlings that were surveyed by eagle biologists after the breeding season were in good condition, had flat tops, brown leaves, whitewash and prey remains. Nests without nestlings were more bleached than nests with nestlings. Classification tree analysis indicated that the presence of a flat top or whitewash were comparable models for data collected mid breeding season (26% misclassification). The presence of a flat top was the best predictor of the presence of nestlings for data collected after the breeding season (8% misclassification). Nest characteristics change during and after breeding activity, so survey timing is important to consider when determining the nest characteristics that best reflect breeding activity. Source


Stojanovic D.,Australian National University | Koch A.J.,Tasmanian Forest Practices Authority | Koch A.J.,University of Tasmania | Webb M.,Australian National University | And 4 more authors.
Austral Ecology | Year: 2014

Tree cavities provide important habitat for wildlife. Effective landscape-scale management of cavity-dependent wildlife requires an understanding of where cavities occur, but tree cavities can be cryptic and difficult to survey. We assessed whether a landscape-scale map of mature forest habitat availability, derived from aerial photographs, reflected the relative availability of mature trees and tree cavities. We assessed cavities for their suitability for use by wildlife, and whether the map reflected the availability of such cavities. There were significant differences between map categories in several characteristics of mature trees that can be used to predict cavity abundance (i.e. tree form and diameter at breast height). There were significant differences between map categories in the number of potential cavity bearing trees and potential cavities per tree. However, the index of cavity abundance based on observations made from the ground provided an overestimate of true cavity availability. By climbing a sample of mature trees we showed that only 5.1% of potential tree cavities detected from the ground were suitable for wildlife, and these were found in only 12.5% of the trees sampled. We conclude that management tools developed from remotely sensed data can be useful to guide decision-making in the conservation management of tree cavities but stress that the errors inherent in these data limit the scale at which such tools can be applied. The rarity of tree cavities suitable for wildlife in our study highlights the need to conserve the tree cavity resource across the landscape, but also the importance of increasing the accuracy of management tools for decision-making at different scales. Mapping mature forest habitat availability at the landscape scale is a useful first step in managing habitat for cavity-dependent wildlife, but the potential for overestimating actual cavity abundance in a particular area highlights the need for complementary on-ground surveys. © 2014 Ecological Society of Australia. Source


Cawthen L.,Tasmanian Forest Practices Authority | Cawthen L.,Cooperative Research Center for Greenhouse Gas Technologies | Cawthen L.,University of Tasmania | Munks S.,Tasmanian Forest Practices Authority | And 2 more authors.
Australian Mammalogy | Year: 2011

Linen thread was built into radio-collars as a weak-link to trial its effectiveness at ensuring that radio-collars did not remain indefinitely on animals if they were not recaptured. Eighty percent of collars with weak-links broke or degraded, resulting in the collars dropping off within 12-45 days. This method may be useful for short-term studies of some species of mammal that are difficult to recapture in order to remove collars. © 2011 Australian Mammal Society. Source

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