A global population assessment of the Chinstrap penguin (Pygoscelis antarctica)

Noah Strycker,Steve Forrest,Chandi Witharana,Heather J Lynch,Michael Wethington,Tom Hart,Alex Borowicz

doi:10.1038/s41598-020-76479-3

Abstract

Using satellite imagery, drone imagery, and ground counts, we have assembled the first comprehensive global population assessment of Chinstrap penguins (Pygoscelis antarctica) at 3.42 (95th-percentile CI: [2.98, 4.00]) million breeding pairs across 375 extant colonies. Twenty-three previously known Chinstrap penguin colonies are found to be absent or extirpated. We identify five new colonies, and 21 additional colonies previously unreported and likely missed by previous surveys. Limited or imprecise historical data prohibit our assessment of population change at 35% of all Chinstrap penguin colonies. Of colonies for which a comparison can be made to historical counts in the 1980s, 45% have probably or certainly declined and 18% have probably or certainly increased. Several large colonies in the South Sandwich Islands, where conditions apparently remain favorable for Chinstrap penguins, cannot be assessed against a historical benchmark. Our population assessment provides a detailed baseline for quantifying future changes in Chinstrap penguin abundance, sheds new light on the environmental drivers of Chinstrap penguin population dynamics in Antarctica, and contributes to ongoing monitoring and conservation efforts at a time of climate change and concerns over declining krill abundance in the Southern Ocean.

Highlights

Chinstrap penguins (Pygoscelis antarctica) are abundant in Antarctica, with past estimates ranging from 3–8 million breeding pairs, and are considered a species of “least concern” by BirdLife International[1], but the population dynamics of this species are not well understood and several studies have highlighted significant declines at monitored s ites[2,3,4,5,6]
The purpose of this paper is to address two research questions: (1) What is the global population and distribution of Chinstrap penguins? and (2) How does updated information on Chinstrap penguin abundance and distribution support or refute current hypotheses of penguin population dynamics around the Western Antarctic Peninsula? This paper provides a status report on our efforts to assemble all the available information on Chinstrap penguin distribution, abundance, and population trends over the past 40 years
Most Chinstrap penguin colonies are in the southwest Atlantic sector of the Southern Ocean, which includes the Antarctic Peninsula and associated islands, including the South Orkney Islands, South Sandwich Islands, and South Georgia Island (Fig. 1)

Summary

Introduction

Chinstrap penguins (Pygoscelis antarctica) are abundant in Antarctica, with past estimates ranging from 3–8 million breeding pairs, and are considered a species of “least concern” by BirdLife International[1], but the population dynamics of this species are not well understood and several studies have highlighted significant declines at monitored s ites[2,3,4,5,6]. Since the 1980s, breeding populations in some areas have been reported to have declined by > 50%2–6,8,9, with notable exceptions in the South Sandwich Islands, at South Georgia Island, and in a few sites near the southern extent of the Chinstrap penguin’s range[4,10]. Because of their dependence on krill (Euphausia spp.) and fish (Pleuragramma antarctica), Chinstrap penguins can be viewed as “marine sentinels” for quantifying environmental change in the Southern Ocean[11]. We discuss how these results fit into the current debate surrounding drivers of penguin population trends in the Antarctic Peninsula region

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Conclusion