Impact of supplementary feeding on the productivity of kakapo Strigops habroptilus breeding on three offshore islands in New Zealand
Published source details
Clout M.N. & Merton D.V. (1998) Saving the kakapo: the conservation of the world's most peculiar parrot. Bird Conservation International, 8, 281-296
Published source details Clout M.N. & Merton D.V. (1998) Saving the kakapo: the conservation of the world's most peculiar parrot. Bird Conservation International, 8, 281-296
The kakapo Strigops habroptilus is a flightless, lek-mating parrot endemic to New Zealand. Originally widespread in native forests and scrublands throughout New Zealand, by the late 1970s the species was known to survive only in Fiordland, south-western South Island, and on Stewart Island (47º00' S, 167º51' E), c.30 km off the south coast of South Island. However, following a severe episode of predation by feral cats Felis catus in the early 1980s, all known kakapo remaining on Stewart Island were translocated to four predator-free offshore islands between 1980 and 1997. Although the adult survival of translocated kakapo was high*, productivity was very low, and following the discovery that birds on Stewart Island bred only during seasons of heavy fruiting of podocarp trees Dacrydium spp., investigations were initiated into the effects of providing supplementary food. As part of a more general overview of the conservation history of the species, this study reviews the impact of supplementary feeding on the productivity of translocated kakapo.
The provision of supplementary foods (nuts, apples and sweet potatoes) at artificial feeding stations was initiated on Little Barrier Island (36º12' S, 175º05' E) in 1989 (James et al. 1991). Supplementary feeding was subsequently also started on Maud Island (41º02' S, 173º53' E) in 1991. Seven of 10 female kakapo on Codfish Island (46º46' S, 167º38' E) were also brought into the supplementary programme after the failure of the crop of rimu Dacrydium cupressinum fruit during the 1992 breeding season.
On Little Barrier Island, there were no known breeding attempts during the first seven years following the translocation of 22 kakapo (nine females and 13 males) in 1982. However, after the initiation of supplementary feeding in 1989, male display activity increased markedly, and between two and four females nested in four of the subsequent six years. Neither of the two females translocated (with four males) to Maud Island bred during 1991-1997, despite the initiation of supplementary feeding in 1991, but a third female, transferred from Little Barrier Island in 1996, did nest in 1998. On Codfish Island, at least four females bred in 1992 (prior to the initiation of supplementary feeding), in synchrony with a heavy fruiting of rimu trees. Despite the subsequent year-round provision of supplementary food to most kakapo on the island, the next breeding season on Codfish was in 1997 (during the next rimu fruiting event), when eight females (including both supplementary-fed and non-fed individuals) were believed to have mated, and six of these went on to nest.
Despite the apparent increase in breeding activity on Little Barrier Island following the onset of supplementary feeding, productivity was low, with around 40% of eggs infertile and the early death or disappearance of nestlings from three nests. Ultimately, just two chicks (both males) survived to independence, from two of 10 nests detected. On Codfish Island, six chicks hatched successfully during the 1992 breeding season, but three of these died in the nest as a result of starvation or probable predation by Polynesian rats Rattus exulans. The remaining three chicks were taken into captivity for hand-rearing, but only one of these (a female) survived, and was released back into the wild in 1997. Of the 12 eggs laid on Codfish during the 1997 breeding season, five were infertile and two more failed to hatch. One of the five chicks that did hatch died immediately after hatching. Because of the failure of rimu crop again in 1997, the chick from the only non-fed female to produce young was taken into captivity for hand-rearing, but ultimately died. A male chick (of a supplementary-fed female) that developed respiratory problems following a spell of bad weather was also taken into captivity, hand-reared successfully and released back into the wild. The two remaining chicks (both male) were successfully raised by their supplementary-fed mothers. The female that nested on Maud Island in 1998, laid three fertile eggs, all of which hatched, and the chicks (one female and two males) were raised to independence.
* For further details, see http://www.conservationevidence.com/ViewEntry.asp?ID=1241.
James K.A.C., Waghorn G.C., Powlesland R.G. & Lloyd B.D. (1991) Supplementary feeding of kakapo on Little Barrier Island. Proceedings of the Nutrition Society of New Zealand, 16, 93-102.
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