The Influence of Proximity of Plantation Edge on Diversity and Abundance of bird species in an exotic pine plantation in north-eastern New South Wales

Abstract

Data were collected in summer and winter in a 15-year-old plantation of Pinus taeda, at Clouds Creek, north-eastern New South Wales. In summer, diversity and abundance of bird species declined over a distance of 900 m into the plantation. However, in winter this progressive decline in bird densities was limited to within the first 200 m of the plantation periphery. At greater distances into the plantation, the floristic and structural characteristics of the vegetation (including windrows) were of more importance than the proximity of the plantation edge in accounting for variations in the abundance and diversity of birds. Food for insectivorous birds (the dominant feeding guild) is probably restricted in the plantation because few local species of invertebrates are likely to be adapted to living on exotic pines; invertebrate mobility as well as abundance is probably less in winter, so that fewer invertebrates enter the plantation from adjacent native forest. Windrows are an important habitat feature contributing to the diversity and abundance of birds within plantations, probably serving as 'corridors' through the alien habitat of exotic pines, thus enabling birds to range further into plantations. For approximately 40 per cent of the plantation life cycle, the influence of proximity of plantation edge on diversity and abundance of bird species is probably of limited importance, particularly in winter. Reducing plantation size in order to increase the diversity and abundance of bird species is not realistic, because plantations would have to be very small. Instead, emphasis should be placed on increasing the structural and floristic diversity of plantations by creating a broad range of successional stages throughout the plantation complex, by enhancing the habitat value of windrows, and by retaining native vegetation within and near plantations.