Declining eastern rockhopper (Eudyptes filholi) and erect-crested (E-sclateri) penguins on the Antipodes Islands, New Zealand

New Zealand's subantarctic Antipodes Islands are of international significance for breeding seabirds. However, penguin populations on the islands are declining. Uncertainty about the extent of this decline has been accentuated by a lack of accurate information on the population size and nest distribution of the penguin species, and the absence of an appropriate methodology for their long-term monitoring. We surveyed the nest abundance and distribution of eastern rockhopper penguins (Eudyptes filholi) and erect-crested penguins (E. sclateri) on the Antipodes Islands from 22 October to 6 November 2011 and compared counts with historical censuses from 1978 to 1995. Presence or absence of colonies previously known to have existed was recorded and counts of all nests within colonies around the islands were undertaken. In total, 42 689 nests of both species were counted over 103 colonies. Of these, 86% of nests (2475 rockhopper and 34 226 erect-crested) were counted accurately from on land. Overall, 24 entire colonies have ceased to exist since 1978, and there was an estimated 23% decline in the number of penguin nests between 1995 and 2011. Despite differences in methodology between surveys, there appears to have been a significant decline in penguins nesting on the Antipodes Islands. Worldwide, most crested penguin species (Eudyptes spp.) are in decline. Since New Zealand is a world hotspot for endemic penguin species, a consistent monitoring system needs to be developed and a monitoring schedule put in place to allow quantification of the scale of these declines. The causes of the declines on the Antipodes also need to be investigated, as they are unlikely to be a result of on-land predation by introduced mammals and human habitat disturbance or destruction, as occurs on the New Zealand mainland.