Kaka

Kākā (Nestor meridionalis) are vulnerable to predation by stoats (Mustela erminea) and possums (Trichosurus vulpecula), particularly when nesting. Without predator control kākā populations decline. Control of stoats and possums both by trapping and aerial application of the poison 1080 leads to increased kākā nesting success. In recent years, many 1080 poison operations have been undertaken to control ship rat (Rattus rattus) and stoat plagues that occur after beech mast. Kākā do not breed every year but breed in anticipation of heavy fruiting.

Artificial barriers, such as nest boxes and metal collars, are sometimes used, with variable success, to exclude predators and/or competitors from tree nests of vulnerable bird species. This paper describes the observed response of captive stoats (Mustela erminea) to a nest box design and an aluminium sheet collar used to protect kaka (Nestor meridionalis) nest cavities. The nest box, a prototype for kaka, was manufactured from PVC pipe. Initial trials failed to exclude stoats until an overhanging roof was added. All subsequent trials successfully prevented access by stoats.

To measure the costs and benefits of an aerial 1080 possum control operation to kereru and kaka in Whirinaki Forest Park, individuals of both species were radio-tagged from October 1998 to June 2002. We monitored birds in one treatment and one non-treatment study area to compare toxin-related mortality, nesting success and survival. The poison operation involved the spreading of non-toxic carrot baits on 1 May 2000, and the toxic baits on 17/18 May 2000.

To enhance the breeding success and survival of kaka (Nestor meridionalis) and mohua (Mohoua ochrocephala), we initiated stoat (Mustela erminea) control in the Eglinton Valley (13 000 ha), Fiordland, New Zealand using a single 40 km line of traps spaced 200 m apart with traps set continuously. This low intensity stoat control regime permitted successful kaka breeding and fledgling survival was high.

The sex ratio of the kaka population inhabiting the Waihaha Ecological Area, Pureora Forest Park was estimated between late October 1994 and January 1995. The observed sex ratio estimate was three males to one female compared to a capture rate (using mist nets) of six to one in the same area between January and June 1994. Females appeared to be less susceptible to capture than males. The skewed sex ratio toward male kaka was significant and suggests that female kaka suffer higher mortality (probably due to predation at the nest) than males.

Food of the North Island kaka (Nestor meridionalis septentrionalis) on Kapiti Island was identified while quantifying the foraging activity of nine radio-tagged birds from March 1991 to January 1992. Additional food types were identified by opportunistic observation of feeding birds and qualitative examination of nestling faeces. A diverse range of food was taken, including wood-boring invertebrates, scale insects, seeds, nectar or pollen, fruits, and sap.

Kaka (Nestor meridionalis meridionalis) studied in Big Bush State Forest spent 35% of their feeding time digging out Ochrocydus huttoni larvae from live mountain beech trunks (Nothofagus solandri: var. cliffortioides).
Larvae of O. huttoni had a high energy value compared to that of other insects. The assimilation efficiency for energy of two captive kaka was 91 j: 3% when fed a diet of O. huttoni.