Science & Research Series N0.17 a Habitat Survey of North Island Kokako in Puketi Forest, Northland

The vegetation structure and composition, and the activities of kokako were studied intensively in five home ranges in Puketi Forest to determine the significance of kauri to kokako, and the likely impacts of logging and browsing mammals upon kokako. Typically, kokako home ranges in Puketi Forest were situated mainly in dissected terrain and contained a great diversity of vegetation types and species. Additionally, some of the vegetation in, or immediately adjacent to kokako home ranges was influenced by disturbance, either natural (cyclone damage, slips) or man-induced (logging, roading). Overall, kokako activities were concentrated mainly on vegetation of upper ridge crests and flanks. Gully bottom vegetation was important for feeding, seasonally. Kokako used plant species generally in proportion to their relative abundance. However, when feeding, they could be quite selective and at times comparatively rare plants featured prominently in their diet. Conversely, some very common species were hardly ever fed on. The composition of the diet changed with season, according to the availability of edible material from individual food-producing species. Some of the principle plant food species eaten by kokako were also highly palatable to browsing mammals, particularly possums. Singing was an important kokako activity in summer. Kauri trees were used particularly (whenever present in a kokako home range) as song posts, owing to their towering stature and tendency to grow on prominent, exposed ridge tops. Kokako spent little time in areas of kauri-dominated forest that had been damaged by logging and roading, and frequented undisturbed sites instead. Logging of kauri stands removed important song platforms, and disrupted the canopy and understorey (which provided most of the food producing species), leaving vegetation that was not favoured by kokako. It was concluded that no further logging take place, that browsing mammals be controlled, and that formal protection status be given to all of Puketi Forest. Further avenues for research have been identified. A full technical report of the study will be published shortly.