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.
King shags (Leucocarbo carunculatus) dispersing to feeding areas from breeding colonies on the Trio Islands and Stewart Island began to leave colonies around dawn, and most had left by mid-morning. Foraging birds were distributed throughout Admiralty Bay, the average distance from the colony was c. 10 km, and were observed only rarely where the water depth was >50 m. Greater areas of mussel farms in inshore waters could potentially affect king shags by restricting the area available for foraging.
The breeding biology of kakapo (Strigops habroptilus) was investigated on offshore island refuges between 1990 and 2002. Male kakapo typically attended their display territories between October to April, with the primary courtship display, “booming”, usually beginning in January and ending in March. Mating was recorded from late December to March, with the median mating date falling in late January. Eggs were laid from early January to late March, with median dates of 24 January on Little Barrier Island and 7 February on Codfish and Pearl Islands. Females typically occupied a nest site eight days after their last mating (n = 44) and laid their first egg two days later (n = 40). Subsequent eggs were laid at three day intervals (n = 41). The mean and modal clutch sizes were 2.53 and 3 respectively, (range = 1 – 4, n = 54). Mean mass of fresh eggs was 40.53g (n = 122). Incubation began immediately after the first egg had been laid and the average incubation period was 30 days (n = 28). Mean nestling and fledgling periods were 72.4 (n = 27) and 246 days (n = 25) respectively. Male chicks began to grow more rapidly than females approximately one third through the nestling period. The mean fledging weights of 14 male and 14 female chicks were 1.93 and 1.72 kg respectively. Male kakapo are capable of mating at five years of age. Three known-age females first nested at 9, 10 and 11 years of age, respectively. Comparison with close relatives suggests that some aspects of kakapo breeding biology are evolutionarily conservative.
The anticoagulant brodifacoum is widely used for the control and eradication of vertebrate pests in New Zealand. During poisoning operations with this toxin, some native birds eat baits and die. Because brodifacoum persists in the environment, other birds may suffer secondary poisoning from eating animals that have ingested the poison baits.We describe here high mortality of New Zealand dotterels (Charadrius obscurus) following an aerial brodifacoum operation at Tawharanui Regional Park, North Auckland, in 2004. At least 50% of the dotterels in the area at the time of the operation disappeared or were found dead; one bird found freshly dead had a high liver level of brodifacoum residue. Sandhoppers (Talorchestia spp.) are a common food item of New Zealand dotterels. Sandhoppers at Tawharanui ate baits and accumulated brodifacoum and provided a potential route for transmission of the toxin to dotterels. Three pied stilts (Himantopus himantopus) and one spur-winged plover (Vanellus miles novaehollandiae) were also found dead. These records appear to be the first to document probable secondary poisoning of shorebirds in New Zealand. There was no apparent mortality of variable oystercatchers (Haematopus unicolor). Measures are suggested to reduce shorebird mortality in future operations of this type. Monitoring of New Zealand dotterels and other shorebirds during other types of poisoning operations in coastal areas is also recommended.
The “hakawai” is a rarely-heard but dramatic nocturnal aerial display performed by Coenocorypha snipe. Although much has been written about the hakawai formerly heard on islands off Stewart Island (performed by the extinct Stewart Is snipe C. aucklandica iredalei), there are few documented reports from other populations. We describe hakawai aerial displays heard on Adams I (Auckland Is snipe C. aucklandica aucklandica), Antipodes I (Antipodes Is snipe C. aucklandica meinertzhagenae), and Campbell I (Campbell Is snipe Coenocorypha undescribed sp.) between 2001 and 2006. These include the 1st records of hakawai on Adams I and Campbell I. Based on characteristic tail feather damage believed to be caused by the display, Campbell Is snipe of both sexes performed hakawai aerial displays more frequently than has been recorded for all other Coenocorypha snipe populations. Male snipe from all 6 populations assessed exhibited a higher frequency of tail feather wear than females, and for the 3 populations with adequate data, males also had lower wing-loadings, indicative of greater flying ability. However, there was no apparent correlation between the frequency of “hakawai” feather wear and wing-loadings when comparing between populations.
The kakapo (Strigops habroptilus) is a nocturnal, herbivorous parrot that shows lek behaviour and does not breed every year. When breeding does occur, egg-laying and incubation in mid-summer are followed by a prolonged period of chick-rearing, with all parental care provided by the female. Breeding years for kakapo are associated with mast seeding years for a range of forest trees and plants, and the periodicity of kakapo breeding is linked with the periodicity of years of large seed and fruit production by their major plant foods. Kakapo are likely to have an annual cycle of gonadal growth and regression driven by the annual cycle of day length, with breeding occurring in years when kakapo respond to cues from a range of plant species that undergo masting. Kakapo breeding is initiated in response to cues that appear in early summer, but in some years there is insufficient food for the rearing of young in the following autumn. Rimu (Dacrydium cupressinum) is an important food source for chick rearing and is likely to provide an important cue for kakapo in areas where rimu is present.