No abstract

The foraging ecology of eucalypt forest and woodland birds was studied on three 10 ha plots in southeastern Australia. Quantitative data were obtained for 41 species of which 31 were insectivorous, eight were nectar-feeders, and two were parrots that fed primarily on eucalypt seeds. Birds-of-prey, large omnivores andfrugiwres were uncommon. Insectivorous birds differed in foraging behaviour, the substrates on which they found prey, and foraging height. Nectar-feeders exploited a variety of carbohydrates including nectar, honeydew, lerp, manna and sap. Nectarivorous birds were separated by foraging behaviour, substrate, height and by the extent to which they used the different types of carbohydrates. Carbohydrates were also an important food resource for some insectivores. By understanding how birds exploit food resources within forest and woodland environments, the features of the environment which need to be conserved or manipulated to manage forest avifaunas can be identified. For example, in addition to the substrates such as foliage and bark, usually associated with the foraging of forest birds, carbohydrates and loose bark were identified as important resources for birds in eucalypt forests and woodlands. The broad importance of these two resources to the avifauna had not been previously appreciated, yet both may be sensitive to environmental changes associated with logging and other forest management practices which alter the composition or age-class structure of forests.

A regional survey of the forests in north-eastern New South Wales recorded eight species of nocturnal forest birds and nine species of arboreal marsupials from 291 sites. Three major environmental gradients accounting for the distribution of these species in north-eastern New South Wales were identified: elevation, forest type (wet forest types having a dense mesic understorey or dry forest types having an open or sparse understorey), and logging intensity. Characteristic assemblages of species were associated with each end of these three gradients. A core group of species occurred across a wide range of environmental conditions, including logged and unlogged forest. Most species occurred with similar frequency in logged and unlogged forest. Implications for forest management are discussed.

The yellow-bellied glider (Petaurus australis), the largest of the exudivorous marsupials, lives in small family groupings and occupies virtually exclusive home ranges. A variety of estimation techniques were used to determine the home-range area of five glider groups. Two sets of data were analysed for each glider group; one included the locations of all observations while the other utilised a subset considered to represent independent observations based on a 3-h interval between consecutive locations. The techniques favoured for estimating home-range area, minimum convex polygon (MCP) and 95% isopleth of the harmonic mean (95% HM), gave mean values of 59 ha and 46 ha, respectively, when all data were included. These values were 28% and 14% larger, respectively, than those estimated with independent data. An extrapolation that accounted for the influence of the number of locations on the area estimated gave a mean MCP value of 63 ha for the five groups. This value was compared with estimates for other exudivorous mammals and is much greater than that predicted from the body weight of this species. The home ranges (defined by the 95% HM) of the five glider groups included different proportions of the seven forest types available in the study area. The forest type in which Eucalyptus ovata predominated was identified as a key habitat. It was the least abundant yet was included in all five home ranges, unlike several of the more abundant forest types which were absent from some home ranges. The above results are discussed in relation to forest management and conservation.

The foraging behaviour of the yellow-bellied glider was observed for more than 3 years in south-eastern New South Wales. The use of different substrates by foraging gliders followed an annual cycle which was correlated with the phenological pattern in the forest. Flowering and bark shedding on eucalypts were the characters of tree phenology most useful for predicting the behaviour of foraging animals. Gliders concentrated their foraging efforts on ephemeral food resources, particularly those obtained from under loose bark; this led to a seasonal pattern in the use of tree species and habitats in the study area. The preferred habitat of P. australis is likely to be characterised by a mosaic of tree-species associations, including those which flower in winter. Smooth-barked eucalypts are important because of the diversity of foraging substrates, and hence food resources, which they provide. The patchy distribution of these gliders may be explained by differences in floristic diversity and the complexity of the habitat mosaic.