The summer distribution, habitat associations and abundance of seabirds in the sub-polar frontal zone of the Northwest Atlantic

Ewan D. Wakefield* (Corresponding Author), David L. Miller, Sarah L. Bond, Fabrice le Bouard, Paloma C. Carvalho, Paulo Catry, Ben J. Dilley, David A. Fifield, Carina Gjerdrum, Jacob Gonzalez-Solis, Holly Hogan, Vladimir V. Laptikhovsky, Benjamin Merkel, Julie A. O. Miller, Peter I. Miller, Simon J. Pinder, Tânia Pipa, Ryan M Peterson, Laura A. Thompson, Paul ThompsonJason Matthiopoulos

*Corresponding author for this work

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Abstract

Biological production in the oceanic zone (i.e. waters beyond the continental shelves) is typically spatially patchy and strongly seasonal. In response, seabirds have adapted to move rapidly within and between ocean basins, making them important pelagic consumers. Studies in the Pacific, Southern and Indian Oceans have shown that seabirds are relatively abundant in major frontal systems, with species composition varying by water mass. In contrast, surprisingly little was known about seabird distribution in the oceanic North Atlantic until recent tracking showed that relative abundance and diversity peak in the Sub-polar Frontal Zone, west of the Mid-Atlantic Ridge, now proposed as a Marine Protected Area. However, absolute seabird abundance, distribution, age and
species composition, and their potential environmental drivers in the oceanic temperate NW Atlantic remain largely unknown. Consequently, we systematically surveyed seabirds and environmental conditions across this area by ship in June, 2017, then modelled the density of common species as functions of environmental covariates, validating model predictions against independent tracking data. Medium-sized petrels (99.8%), especially Great Shearwaters (Ardenna gravis, 63%), accounted for the majority of total avian biomass, which correlated at the macroscale with net primary production and peaked at the sub-polar front. At the mesoscale, the density of each species was associated with sea surface temperature, indicating zonation by water mass. Most species also
exhibited scale-dependent associations with eddies and fronts. Approximately 51, 26, 23, 7 and 1 % of the currently estimated Atlantic populations of Cory's Shearwaters (Calonectris borealis), Great Shearwaters, Sooty Shearwaters (A. grisea), Northern Fulmars (Fulmarus glacialis) and Leach’s Storm-petrels (Oceanodroma leucorhoa) occurred in the area during our survey, many of which
were undergoing moult (a vital maintena nce activity). For some species, these estimates are higher than suggested by tracking, probably due to the presence of immatures and birds from untracked populations. Our results support the conclusion that MPA status is warranted and provide a baseline against which future changes can be assessed. Moreover, they indicate potential drivers of seabird abundance and diversity in the oceanic zone of the North Atlantic that should be investigated further.
Original languageEnglish
Article number102657
Number of pages21
JournalProgress in Oceanography
Volume198
Early online date8 Aug 2021
DOIs
Publication statusPublished - 30 Nov 2021

Bibliographical note

Acknowledgements
Funding was provided by the UK Natural Environmental Research Council (NERC) [grant number NE/M017990/1] and Fundação para a Ciência e a Tecnologia (FCT) [grant numbers MARE -UIDB/04292/2020 and UIDP/04292/2020]. Remotely-sensed data were supplied by the NERC Earth Observation Data Acquisition and Analysis Service (NEODAAS) and the Copernicus Marine Service. Permission to track birds was provided by the Tristan da Cunha Government
(Gough Island), the Falkland Islands Government (permit R09/2016, Kidney Island), the Região Autónoma dos Açores (permit 84/2016/DRA, Corvo), and Orkney Islands Council and BTO (Eynhallow). Logistical support was provided by the RSPB, FitzPatrick Institute of African Ornithology and South African National Antarctic Programme (Gough Island), the South Atlantic Environmental Research Institute (Kidney Island), and Sociedade Portuguesa para o Estudo das Aves (Corvo). Stefan Schoombie, José Pedro Granadeiro and Ewan Edwards provided raw GPS data to inform movement parameters used in the shearwater GLS data analysis and Rob Ronconi, Alex Bond and Gail Davoren provided advice on the study design. Support for NOFU loggers and analysis was provided through the SEATRACK project http://www.seapop.no/en/seatrack/, funded by the Norwegian Ministries of Climate and Environment, and Foreign Affairs and the Norwegian Oil and Gas Association. We are very grateful to Captain Antonio Gatti and the crew of the RRS Discovery, the many fieldworkers who deployed/recovered the GLS tags and Igor Belkin, who generously provided constructive advice on the study design and manuscript.

Keywords

  • distance sampling
  • habitat model
  • mesoscale eddy
  • marine protected area
  • procellariiformes
  • shearwater

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