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Erect-crested penguins on the Bounty Islands: population size and trends determined from ground counts and drone surveys

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Mattern, T, Rexer-Huber, K, Parker, G, Amey, J, Green, CP, Tennyson, AJD, Sagar, PM and Thompson, DR 2021 , 'Erect-crested penguins on the Bounty Islands: population size and trends determined from ground counts and drone surveys' , Notornis, vol. 68 , pp. 37-50 , doi: 10.6084/m9.figshare.19709476.

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Abstract

In October 2019, an expedition to the subantarctic Bounty Islands provided the opportunity to conduct comprehensive ground counts of erect-crested penguins to assess population size and compare numbers to previous surveys. The entirety of Proclamation Island, an erect-crested penguins' stronghold, was surveyed and number of active penguin nests was determined via ground counts. Drone surveys aiming at assessing seal numbers, provided high-resolution aerial photography allowing spatial analysis of penguin nest densities on four islands, i.e. Proclamation, Tunnel, Spider, and Ranfurly Islands. A total of 2,867 penguin nests were counted on Proclamation Island between 24 and 29 October. Adjusting for the earlier timing of the survey compared to counts conducted since 1997, nest numbers were only marginally lower (~2.4%) than in 1997 and 2004 suggesting that the penguin population has remained stable for the past 20 years; a ~10% reduction in penguin numbers in 2011 seems to be related to warmer than average ocean temperatures that year. Density analysis from drone imagery showed highly heterogenous distribution of penguin nests, with birds preferring areas sheltered from prevailing south-westerly winds. This also means that a previous estimate from 1978 which relied on uniform extrapolation of nest densities to what was assumed to suitable breeding areas substantially overestimated the true population size, thereby contributing to the species current 'endangered' threat ranking.

Item Type: Article
Authors/Creators:Mattern, T and Rexer-Huber, K and Parker, G and Amey, J and Green, CP and Tennyson, AJD and Sagar, PM and Thompson, DR
Keywords: erect-crested penguin, nest counts, drone survey, nest densities, population trends, New Zealand fur seal, subantarctic islands, Bounty Islands
Journal or Publication Title: Notornis
Publisher: Ornithological Society of New Zealand Inc.
ISSN: 0029-4470
DOI / ID Number: 10.6084/m9.figshare.19709476
Copyright Information:

© 2021 The Ornithological Society of New Zealand Inc. This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) License (https://creativecommons.org/licenses/by/4.0/). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

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