Bird use of native trees retained in young eucalypt plantations: species richness and use of hollows

Context. The retention of mature eucalypts in plantation areas is expected to have biodiversity benefits, especially for animals with specific requirements such as hollow-using species. Aims. The aim of the current study was to examine the degree to which retained trees embedded in young (<= 3 years old) eucalypt plantation provide habitat for birds, whether as a perching/foraging resource for all bird species or as a potential shelter/breeding site for hollow-using species. Methods. We examined bird use of remnant trees in young eucalypt plantations at five sites in northern Tasmania. Four 20-min surveys were done on 214 trees (101 of these had visible hollows) over two breeding seasons (2007 and 2008). Bird activity at a hollow was recorded during all four surveys, whereas the number of bird species observed in a tree was only recorded during two surveys in the first breeding season. The relationship between both species richness and hollow use with site and tree variables was explored using hierarchical partitioning. Key results. Bird species richness at a tree was most strongly related to which of the five properties the tree was located on. This may be due to differences in soil fertility and/or the amount of forested area within and around the property. Birds were observed investigating 50 hollows on 36 trees. More than one hollow was used in 10 trees and hollow use was most strongly related to hollow abundance in a tree. High re-use of particular trees (n = 15) and hollows (n = 16) indicates that retained trees vary in the type and quality of habitat they provide for hollow-using birds. The most common hollow users observed were the common starling (Sturnus vulgaris) and the striated pardalote (Pardalotus striatus). Conclusions and implications. Retaining trees in plantation areas, particularly trees with special features such as hollows, should be encouraged to provide habitat for birds and help contribute to the maintenance of bird diversity in an area.