Eucalypt plantations as habitat for birds on previously cleared farmland in south-eastern Australia

Published source details Loyn R.H., McNabb E.G., Macak P. & Noble P. (2007) Eucalypt plantations as habitat for birds on previously cleared farmland in south-eastern Australia. Biological Conservation, 137, 533-548.
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Summary

In parts of Australia, extensive areas of deforested land are being reforested with native eucalypt species to establish commercial plantations. This study assessed the extent to which these plantations contributed to conservation of forest bird diversity in rural Victoria, south-eastern Australia.

Study sites: Sites were selected in two regions (north-east and central-west) of Victoria, south-eastern Australia, where many eucalypt plantations have been established. Each site comprised a 1-ha area of: cleared farmland (n=25), eucalypt plantation (n=58) or remnant native forest (n=22).

Bird surveys: At each site, birds were surveyed twice, once in spring/summer (October- December) and in winter (May-August) using a standard timed area-search on foot (1-ha in 10 min); numbers of birds seen or heard were recorded by species. Sites were surveyed in two seasons: 2003/04 (north-east) and 2004/05 (central-west).

Habitat variables: Assessments were made of grass cover, height and signs of grazing by domestic stock. Cover values were estimated for tall (>2 m tall) and small shrubs (<2 m tall), small branches, native mistletoes (mainly drooping mistletoe Amyema pendulum) and non-native blackberry Rubus fruticosus. Other site data collected were: landform (flats or lower slopes; mid or upper slopes), gradient (flat or gentle, <10º; steep >10º) and slope aspect, species of planted trees, numbers of retained older trees, fallen logs and branches.

Landscape variables: Some landscape-scale variables (e.g. area of forest cover, native grassland, cleared farmland and wetlands) for each site were compiled from satellite imagery. Computer modelling was used to assess those that contributed to the value of plantations for particular groups of bird species (or guilds).

Average abundance of forest/woodland birds was highest in native forest (c.10.1), a little lower in eucalypt plantations (c.8.9) with low numbers in farmland (c.1.3). However, bird guilds differed somewhat between plantations and native forest e.g., canopy and tall shrub layer foraging insectivores were as common in plantations as in native forest; shrub foragers used the young planted eucalypts as if they were tall shrubs. Open forest floor foragers were more common in plantations than native forest, including several species that have declined in natural woodlands.

Nectarivores, carnivores and birds that forage among low shrubs were less common, and insectivores that forage from eucalypt bark (small-size, hole-nesters) were very scarce in plantations, compared to native forest. Measures to enhance habitat for the latter guild might include planting of rough-barked eucalypts in addition to smooth-barked species, and provision of artificial hollows.

Conclusions: The study shows that eucalypt plantations can provide habitat for some forest birds and the authors consider that they may be of special value in regions where native forest has been severely depleted. However, it is evident that plantations do not provide the full array of habitats found in native forest and hence some bird guilds are lacking or depauperate. Retention of remnants of native forest (e.g. old trees and forest patches) within plantations is considered a priority.

Computer models indicated the greater importance of on-site habitat variables (as opposed to the influence of surrounding landscape features) in explaining the abundance of bird guilds.

Note: If using or referring to this published study, please read and quote the original paper, this can be viewed at:

http://www.sciencedirect.com/science/journal/00063207