New Zealand Journal of Ecology (2016) 40(2): 235- 249

Mercury Islands and their role in understanding seabird island restoration

Research Article
David R. Towns* 1,2
Stephanie B. Borrelle 2
Joshua Thoresen 2
Rachel T. Buxton 3
Annette Evans 4
  1. Science and Policy Group, Department of Conservation, Private Bag 68 908, Newton, Auckland 1145, New Zealand
  2. Institute for Applied Ecology, Auckland University of Technology, Auckland 1142, New Zealand
  3. Department of Zoology and Centre for Sustainability: Agriculture, Food, Energy, Environment, University of Otago, Dunedin 9054, New Zealand
  4. School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
*  Corresponding author

The progressive removal of invasive mammals from the Mercury Islands has led to over 25 years of field study designed to test the processes of restoration and natural recovery of these seabird-driven island ecosystems. Resulting from this work, four key restoration questions can now be identified as fundamental to designing island restoration programmes. The questions are: what is the regional context of the island (biogeography); how does each island ecosystem operate (ecosystem function); how have invasive species changed the ecosystem (response effects); and how can progress towards a restoration goal be defined (outcome measures)? Examples of how these questions influenced restoration in the Mercury Islands are provided with Korapuki Island as a case study. However, unpredicted and subtle responses can eventuate. In the Mercury Islands these included a hitherto unknown honeydew parasite-bird-gecko food web and subtle effects of rats on plant regeneration. Promising outcome measures of restoration progress are now being developed, including indices of marine influence using stable isotopes of nitrogen and the use of network analysis to analyse the composition of invertebrate food webs.