Forest Size and the Future of the kokako

Forest and Bird, Volume 17, Issue 4, 1 November 1986, Page 9

Forest Size and the Future of the kokako

A direct relationship between the size of a forest patch on the mainland, and the number of native forest birds present, exists in similar form to that for landbridge islands. This graph (compiled from data collected by a Wildlife Service survey in the King Country, and analysed by Colin Ogle) highlights forests in which kokako are still present and from which they disappeared in the last 20 years. The birds have gone from six of seven patches of 200-1000 ha which contained them 20 years ago, and from six of the eleven patches between 1000 and 10,000 ha in area. The process Of loss is clearly continuing and is remarkable for its speed some of these forest ‘patches’ have been so for less than 100 years, a mere tick of history’s natural clock! The line on the graph denotes the ‘average’ relationship and indicates the number of species which, on average, will occur in a forest patch of a

particular size. All forests now containing kokako lie above the line and thus can be expected to lose one or more species. Island biogeographic studies suggest that it is the most highly endemic species, with their low breeding rate and demand for large space, that will go before others a precise description of kokako!

Kokako failed to remain on Little Barrier Island (30,000 ha) and on smaller islands; the two largest forests in this set are Pureora (24,000 ha) and Whareorino (30,000 ha). What will this graph look like in another 20 years?

y = 2.32842.113 log x 10Number © Kokako still present of ZA, Kokako present within native 5- past 20 years bird Not known to have kokako species 10 100 1000 10000 Forest area (ha)

Number of native forest bird species in forest patches in the survey area. Patches with kokako and those which had kokako within the past 20 years are highlighted.