Effects of Plantation Forestry on Birds in New Zealand

Abstract

The relative densities of birds were compared, vegetation profiles measured and bird food resources assessed in seven exotic conifer plantations and 5 areas of native Nothofagus forest in New Zealand. Of 16 native bird species, 7 were most abundant in native forest and 2 in conifer plantations. None of the 10 introduced birds preferred native forest, but at least seven were commonest in plantations. There was no significant relationship between overall bird species richness (BSR) and foliage height dirversity (FHD). However, when introduced and native birds were considered separately, the BSR of introduced species was negatively correlated with FHD whereas BSR of native birds was positively correlated with FHD. Several introduced passerines preferred structurally simple plantations, but there were always more native bird species in native forest than in plantations. The distribution of birds between areas was largely explained by the differing availability of food such as fruit and honeydew, but for some species vegetation structure or the presence of tree-holes for nesting may be important factors. The native birds which suffer most from replacement of native forest with conifer plantations are frugivores, nectar-feeders and hole-nesters. Conservation of these species in large exotic forests is best achieved by retaining areas of native forest within conifer plantations.