Publications Archive

This study provides a first description of breeding biology of the South Island saddlebacks (Philesturnus carunculatus carunculatus) and the first comparisons with North Island saddlebacks (P.c. rufusater), using data collected from Ulva (Stewart Island), Breaksea (Fiordland) and Motuara (Marlborough Sounds) Islands, New Zealand. We found courtship and copulation behaviour to be similar to that of North Island saddlebacks. So too were nest locations, heights and materials, with nest materials determined by their proximity to the nest site. On Motuara and Ulva Islands, most nests were located in natural cavities (54% and 80%, respectively), while on Breaksea Island, 67% of nests were in flax (Phormium cookianum). In the recently established Ulva Island population, saddlebacks had a median and maximum clutch size of two and laid a maximum of two clutches. This contrasts with translocated island populations of North Island saddlebacks where up to four-egg clutches and four clutches per season have been recorded for pairs breeding in the first few seasons post-release. Incubation and brooding behaviour was like that described for North Island saddleback. A small number of yearlings bred successfully on Ulva Island (0.18 birds/ha), but no yearlings bred on Motuara (0.42 birds/ha) and Breaksea (0.42 birds/ha) islands.

Northern giant petrel (Macronectes halli) populations are thought to be increasing at some locations around the world, decreasing at others. The size and status of their breeding populations within the New Zealand region, in particular, is poorly understood: reliable population estimates have never been made at 3 of the 5 breeding locations. A survey of pre-fledging northern giant petrel chicks on Antipodes Island, New Zealand during Jan 2000 yielded a count of 130. The total population was estimated to be c. 230 breeding pairs. Because of an absence of accurate historical surveys, the status of the Antipodes Is population is unknown.

The South Island takahe (Porphyrio hochstetteri), an endangered flightless rail, has been released on 4 predator-free islands to reduce the risk of its extinction. To determine the ability of these islands to support takahe populations, we studied takahe home range size and carrying capacity on one of the islands. We plotted the location of 4 takahe family groups (13 individuals) from Nov 1994 to Oct 1995 on Tiritiri Matangi Island. Mean home range size (95% Minimum Convex Polygon) was 20.7 ha, and tended to be smaller when the proportion of suitable habitat within each home range was higher. We estimate that Tiritiri Matangi can support up to 8 breeding pairs, based on the availability of suitable habitat and estimated individual habitat requirements. However, this number is likely to change in the future depending on the influence of population density increases and successional habitat changes on takahe spatial requirements.