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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.