McDowall Philip

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  • Article
    Multi-modal survey of Adélie penguin mega-colonies reveals the Danger Islands as a seabird hotspot
    (Nature Publishing Group, 2018-03-02) Borowicz, Alex ; McDowall, Philip ; Youngflesh, Casey ; Sayre-McCord, Thomas ; Clucas, Gemma V. ; Herman, Rachael ; Forrest, Steven ; Rider, Melissa ; Schwaller, Mathew ; Hart, Tom ; Jenouvrier, Stephanie ; Polito, Michael J. ; Singh, Hanumant ; Lynch, Heather J.
    Despite concerted international effort to track and interpret shifts in the abundance and distribution of Adélie penguins, large populations continue to be identified. Here we report on a major hotspot of Adélie penguin abundance identified in the Danger Islands off the northern tip of the Antarctic Peninsula (AP). We present the first complete census of Pygoscelis spp. penguins in the Danger Islands, estimated from a multi-modal survey consisting of direct ground counts and computer-automated counts of unmanned aerial vehicle (UAV) imagery. Our survey reveals that the Danger Islands host 751,527 pairs of Adélie penguins, more than the rest of AP region combined, and include the third and fourth largest Adélie penguin colonies in the world. Our results validate the use of Landsat medium-resolution satellite imagery for the detection of new or unknown penguin colonies and highlight the utility of combining satellite imagery with ground and UAV surveys. The Danger Islands appear to have avoided recent declines documented on the Western AP and, because they are large and likely to remain an important hotspot for avian abundance under projected climate change, deserve special consideration in the negotiation and design of Marine Protected Areas in the region.
  • Article
    Pan-Antarctic analysis aggregating spatial estimates of Adélie penguin abundance reveals robust dynamics despite stochastic noise
    (Nature Publishing Group, 2017-10-10) Che-Castaldo, Christian ; Jenouvrier, Stephanie ; Youngflesh, Casey ; Shoemaker, Kevin T. ; Humphries, Grant ; McDowall, Philip ; Landrum, Laura ; Holland, Marika M. ; Li, Yun ; Ji, Rubao ; Lynch, Heather J.
    Colonially-breeding seabirds have long served as indicator species for the health of the oceans on which they depend. Abundance and breeding data are repeatedly collected at fixed study sites in the hopes that changes in abundance and productivity may be useful for adaptive management of marine resources, but their suitability for this purpose is often unknown. To address this, we fit a Bayesian population dynamics model that includes process and observation error to all known Adélie penguin abundance data (1982–2015) in the Antarctic, covering >95% of their population globally. We find that process error exceeds observation error in this system, and that continent-wide “year effects” strongly influence population growth rates. Our findings have important implications for the use of Adélie penguins in Southern Ocean feedback management, and suggest that aggregating abundance across space provides the fastest reliable signal of true population change for species whose dynamics are driven by stochastic processes.