Re-constructing historical Adelie penguin abundance estimates by retrospectively accounting for detection bias

• Published in: PLOS ONE
• Main Authors: Southwell, C, Emmerson, L, Newbery, K, McKinlay, J, Kerry, K, Woehler, E, Ensor, P
• Format: Article in Journal/Newspaper
• Language: English
• Published: Public Library of Science 2015
• Subjects: Biological Sciences; Ecology; Population ecology; East Antarctica; Adelie penguin; Antarc*; Antarctica
• Online Access: https://doi.org/10.1371/journal.pone.0123540; http://www.ncbi.nlm.nih.gov/pubmed/25909636; http://ecite.utas.edu.au/105911

Seabirds and other land-breeding marine predators are considered to be useful and practicalindicators of the state of marine ecosystems because of their dependence on marineprey and the accessibility of their populations at breeding colonies. Historical counts ofbreeding populations of these higher-order marine predators are one of few data sourcesavailable for inferring past change in marine ecosystems. However, historical abundanceestimates derived from these population counts may be subject to unrecognised bias anduncertainty because of variable attendance of birds at breeding colonies and variable timingof past population surveys. We retrospectively accounted for detection bias in historicalabundance estimates of the colonial, land-breeding Adlie penguin through an analysis of222 historical abundance estimates from 81 breeding sites in east Antarctica. The publishedabundance estimates were de-constructed to retrieve the raw count data and then re-constructedby applying contemporary adjustment factors obtained from remotely operatingtime-lapse cameras. The re-construction process incorporated spatial and temporal variationin phenology and attendance by using data from cameras deployed at multiple sitesover multiple years and propagating this uncertainty through to the final revised abundanceestimates. Our re-constructed abundance estimates were consistently higher and more uncertainthan published estimates. The re-constructed estimates alter the conclusionsreached for some sites in east Antarctica in recent assessments of long-term Adlie penguinpopulation change. Our approach is applicable to abundance data for a wide range ofcolonial, land-breeding marine species including other penguin species, flying seabirds andmarine mammals.