Nest-site selection by black sparrowhawks Accipiter melanoleucus: Implications for managing exotic pulpwood and sawlog forests in South Africa

This study provides timber growers with silvicultural guidelines for establ ishing and maintaining nest-tree habitat for native black sparrowhawks (Acc ipiter melanoleucus) in commercial planted forests in South Africa. In this country, exotic eucalypts and pines are planted principally for pulpwood a nd sawlog production. Nineteen nests were sampled in indigenous forests and 58 nests in exotic forests. Although mean nest heights differed between in digenous and exotic trees. in all trees, nests were positioned, on average, at 64% of tree height. Black sparrowhawks nested near stand edges, probabl y seeking a compromise between nesting adjacent to open hunting habitat and selecting an insulated tree from within the forest. Black sparrowhawks nes ted in tall trees ((X) over bar = 18-33 m for different tree species classe s) with a large diameter (>60 cm). Unfortunately, the South African pulpwoo d and sawlog industry employ short rotations (<16 years) and high tree dens ities (>700 trees/ha) that do not allow the trees to attain the characteris tics suitable for black sparrowhawk nesting sites. Eucalypt and pine nest s tands must be of 25 x 25 m minimum size and incorporate 10 trees at minimum heights of 21 and 18 m and diameters of 37 and 35 cm, respectively. If suc h nest-tree stands are set aside as islands in a sea of commercial forests, and black sparrowhawks and other forest raptors nest in them, timber growe rs will improve the tree-nesting raptor diversity of planted forests. If, h owever, these raptors prey upon species of conservation importance, the man agement recommendations could be reversed to limit the potential for predat ion.