Hiscock J.A.,Southern Islands |
Chilvers B.L.,Marine Species and Threats
New Zealand Journal of Ecology | Year: 2014
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 flholi) 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. © New Zealand Ecological Society.
Chilvers B.L.,Aquatic and Reporting Unit |
Chilvers B.L.,Massey University |
Baker G.B.,University of Tasmania |
Baker G.B.,Latitude |
And 4 more authors.
Polar Biology | Year: 2015
The Auckland Island shag (Phalacrocorax colensoi) is endemic to New Zealand and restricted to the subantarctic Auckland Islands. The species is classified as “Vulnerable” under the New Zealand threat classification systems. The total breeding population is estimated at <1000 pairs, with Enderby Island considered to be the stronghold for the species. The trend of the population is unknown, and it has been recommended a census of the entire adult population be conducted once a suitable methodology has been developed. The objective of this research was to examine census methods to estimate population size for the Auckland Island shag. Three census methods were trialled on Enderby Island during the 2011/2012 breeding season: (a) boat-based counts; (b) aerial photography using a helicopter and; (c) direct counts from the ground. The aerial photographic survey recorded 1889 pairs of Auckland Island shags breeding on Enderby Island during the 2011/2012 breeding season. In comparison, boat-based and ground count surveys recorded lower population sizes by 27 and 26 %, respectively. This research provides the first comparable methodology and baseline population estimate for the breeding stronghold of this threatened seabird and forms the basis for long-term population monitoring. All methodologies examined here could be used for other cliff-nesting seabird species; however, these results indicate a level of bias may be present for any survey method. © 2015 Springer-Verlag Berlin Heidelberg