Welcome the new native?

Forest and Bird, Issue 279, 1 February 1996, Page 8

Welcome the new native?

Ian Close

NEW ZEALAND HAS a new native bird — from Australia. The Nankeen night heron (Nycticorax caledonicus) has been confirmed as breeding — at Jerusalem on the Whanganui River. Under the Wildlife Act a self-introduced bird receives automatic status and protection as a New Zealand native. The heron has never before been confirmed as breeding in New Zealand. They’ve been spotted around the country either in pairs or singly but not in the Wanganui area until two years ago, when up to a dozen were seen in an area between Hipango Park and Pipiriki. Only last November was DoC able to confirm that it bred there. Despite DoC’s description of the discovery of the breeding population as an "exciting find", the establishment of the heron and its inclusion as a protected native species raises some interesting questions. Should self-introduced species of birds gain this automatic and venerable status? There is no information at this stage as to how the heron might impact on more established native fauna, but presumably it already competes with indigenous birds and other animals for food and resources.

A sizeable proportion of the New Zealand avifauna comprises birds that have close relatives in Australia and that have arrived here with the help of the prevailing westerly winds and currents. In evolutionary terms they are recent additions to the New Zealand native biota. Such birds include the kotuku or white heron, morepork, harrier hawk and pukeko. Their arrival in our environment is part of the natural process of change that all ecosystems undergo and no one would quarrel with their genuine status as native birds. But there is a growing group of arrivals from across the Tasman that have established breeding populations only since the major humaninduced environmental changes of the past 200 years. There are at least ten such birds including the royal spoonbill, white-faced heron, silvereye, welcome swallow, blackfronted dotterel, hoary-headed grebe and spur-winged plover. Due to the recentness of their arrival, and the likely on-going recruitment from Australia, most of these birds are genetically indistinct from their Australian relatives. An average of a new species every 20 years is well above what one would expect as the

natural rate of self-introduction. Obviously if New Zealand was still a country of predominantly dense rainforest, rather than predominantly open pasture, then species such as the spurwinged plover which prefer the latter habitat would have been less likely to have established breeding populations. It is possible also that habitat changes in Australia, creating large populations of certain advantaged species have contributed to the increase in arrivals here. One might question whether there is a useful ecological distinction between the deliberate introduction of a bird such as the magpie, or changing the environment with the result that another species can gain a foothold and thrive. The recent sighting near Auckland of spur-winged plovers destroying eggs of New Zealand dotterel — total population under 2,000 — suggests more discriminating criteria might be needed in providing Wildlife Act protections. Certainly in the damaged natural world of Aotearoa, the status of self-introduced birds should be considered case by case, especially in relation to their impacts on this country’s threatened endemic fauna.