Publications Archive

Foraging deficiencies and supplementary feeding play critical roles in kakapo (Strigops habroptilus) breeding biology and conservation. We present a framework for the analysis of complex nutritional data (called the geometric framework – GF) which may contribute further understanding of the relationships between natural foods, supplementary feeding and kakapo reproduction. We outline the basic concepts of the approach, and illustrate its application using data for the protein, lipid and calcium content of a natural food (green fruits of rimu Dacrydium cupressinum) and a supplementary feed (“muesli”). We provide some pointers for the broader application of GF to the problem of kakapo supplementary feeding, and close with a brief review of a literature which suggests that calcium might be a key limiting factor in kakapo reproduction. We hypothesise that supplementary foods with low macronutrient:calcium ratios are likely to be most effective in supporting increased reproduction.

A growing literature indicates that genetic factors have a significant impact on the persistence of populations and hence play an important role in species recovery. Here, I review the role of genetic research in the recovery program of the critically endangered kakapo (Strigops habroptilus). By using three examples of how genetics has guided kakapo managers (molecular sexing, quantification of genetic diversity and confirmation of paternity from known matings), I highlight the important contribution genetics has made to kakapo recovery. I also explore three new avenues of research (genetic diversity at genes for disease resistance, molecular ageing, and genetic similarity and hatching success), all of which may have important implications for future conservation management of kakapo. As such, this review demonstrates that genetic research is an integral part of kakapo recovery.

The natural diet of the kakapo (Strigops habroptilus) is exclusively herbivorous. The bird breeds synchronously with the heavy fruiting or “masting” of certain plant species, including rimu (Dacrydium cupressinum), at intervals of 2 – 5 years, and did so in 2002 on Codfish Island (Whenua Hou) in southern New Zealand. Crop contents of kakapo chicks of 10 – 30 and 31 – 43 days of age, and samples of rimu fruit (entire fruit, red aril, green aril and seed) were collected and chemically analysed for dry matter, organic matter, crude protein, fatty acids, amino acids, fibre, simple sugars and minerals. The crop content samples contained predominantly carbohydrates (76 – 81 % by dry wt.), crude protein (7 – 13 %) and fatty acids (6 – 7 %). Entire rimu fruit contained 7.2 % crude protein, 10.9 % fatty acids, and 78 % carbohydrate predominantly of cellulose, hemicellulose and lignin. The red aril, green aril and seed nutrient composition were similar with the exception of the seed fatty acid profile. There was a large degree of similarity in the nutritional composition of the entire rimu fruit and the crop contents, supporting field observations of the time that female kakapo were feeding almost exclusively entire rimu fruit to their chicks. The nutrient profiles provide the first detailed descriptions of the diet of growing kakapo chicks which can guide the development of supplements and artificial rearing diets for this species. The diet of kakapo chicks up to 60 days of age appears to have a low concentration of essential nutrients and high indigestible matter content when compared with other species, consistent with specialised anatomical features and foraging behaviour of this parrot.

Gray studied the last natural mainland population of kakapo in Fiordland in the 1970s. Between 1974 and 1977 all 15 male birds located occupied home ranges high on the sides of valleys in areas of diverse vegetation associated with the tree line or avalanche and alluvial fans. Track-and-bowl systems were frequently positioned on the crests of ridges and knolls on well-drained sunny slopes. Studies of feeding sign and of faecal content using cuticle analysis provided detail of kakapo diet, confirming the bird to be an herbivore. About 80 species of plants were eaten in Fiordland. The kakapo bill is adapted to crushing and extracting nutrients and retaining fibre which is expelled as distinctive ‘chews’. A preliminary study of the nutrients in kakapo food suggested that the birds selected the most nutritious plant parts and species.

The recent productivity and survival of the critically endangered kakapo (Strigops habroptilus) is summarised and its population trajectory in a variety of circumstances is modelled by simulation. Simulated kakapo population growth rates decline with decreasing intensity of management, and unmanaged kakapo on Codfish Island increase only slowly and have a significant risk of declining. Kakapo on islands where more than one fruiting species triggers their breeding have much higher growth rates than kakapo on islands where only rimu (Dacrydium cupressinum) triggers their breeding. The models predict that kakapo will reach a predetermined population milestone of 53 females in 2 – 6 years depending on the number of fruiting species that trigger breeding. At this milestone the intensity of conservation management will be reduced. Conservation management will be further reduced at a second predetermined milestone of 150 females in 19 – 37 years.

Results from an analysis of plant remains found in faecal droppings of kakapo (Strigops habroptilus) collected from 1981 to 1998 on Codfish Island (Whenua Hou) and Stewart Island, were analysed statistically to identify patterns in the birds’ diet related to breeding. Females were more likely to have eaten podocarp fruit or leaves of trees or shrubs; males to have eaten fern and Lycopodium rhizomes, monocots (in breeding years), and manuka fruit (in non-breeding years). Podocarp fruits were much more prevalent in kakapo diets in breeding than in non-breeding years. When podocarp fruits were available in breeding years, kakapo were less likely to have eaten several other foods. Conversely, Blechnum fern fronds appeared more frequently in the droppings of females in breeding than in non-breeding years. As podocarp fruits increased in prevalence in the diets of both males and females during the summers of breeding years, the incidence of many other foods declined. The incidence of Hall’s totara leaf in the diet of females increased during summer in non-breeding years, but decreased in breeding years.

We recorded the fate of brown kiwi (Apteryx mantelli) eggs collected from Northland forests for artificial incubation at Auckland Zoo. The hatchability of eggs of different ages were combined with known rates of egg losses in the wild to derive models which predicted that optimal hatching success (>64%) was when the oldest egg in a brown kiwi nest was 41-57 days old at the time the eggs were collected. Collection before this interval risked egg failure resulting from unknown developmental problems associated with artificial incubation of freshly-laid eggs, whereas later collection of clutches risked failures in the wild before the eggs were collected.

Information on the breeding ecology of Auckland Is snipe (Coenocorypha aucklandica aucklandica), Antipodes Is snipe (C. aucklandica meinertzhagenae), and Campbell Is snipe (Coenocorypha undescribed sp.) is summarised. Auckland Is snipe laid between Sep and Jan (peak late Nov), whereas Antipodes Is snipe laid from Aug to early Nov, with a 2nd pulse of breeding from late Jan to Mar. The 5 breeding events recorded for Campbell Is snipe were from clutches estimated to have been commenced between 11 Nov and 8 Jan. All 3 taxa laid 2 large eggs (each 19-22% of female body weight) in nests that were well concealed amid dense vegetation. Chicks left the nest soon after hatching, with each chick cared for by a single adult. Exceptions to this were adult Auckland Is snipe seen with 2 or 3 young chicks on 3 occasions. Chicks remained with adults until down-free and capable of flight. The only notable differences from the more thoroughly-studied Snares Is snipe (C.aucklandica huegeli) and Chatham Is snipe (C. pusilla) were the earlier breeding by Antipodes Is snipe, and its bimodal breeding season. Snipe were encountered more frequently on the Auckland Is (0.6 person–h-1 of walking on Adams I) than on Antipodes I (0.2 person–h-1) and this was also reflected in the frequency with which breeding events were recorded. We suggest that the impact of house mice (Mus musculus) on the invertebrate food supply available for snipe is the most plausible explanation for the much lower abundance of snipe on Antipodes I.