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MEPS 599:239-251 (2018)  -  DOI:

Moult location and diet of auks in the North Sea inferred from coupled light-based and isotope-based geolocation

Katie St. John Glew1,*, Sarah Wanless2, Michael P. Harris2, Francis Daunt2, Kjell Einar Erikstad3,4, Hallvard Strøm5, Clive N. Trueman1

1Ocean and Earth Science, University of Southampton, Waterfront Campus, Southampton SO143ZH, UK
2Centre for Ecology & Hydrology, Bush Estate, Penicuik EH26 0QB, UK
3Norwegian Institute for Nature Research, Fram Centre, 9296 Tromsø, Norway
4Centre for Biodiversity Dynamics, Department of Biology, Norwegian University of Science and Technology, 7491 Trondheim, Norway
5Norwegian Polar Institute, Fram Centre, Postbox 6606 Langnes, 9296 Tromsø, Norway
*Corresponding author:

ABSTRACT: Many pelagic seabirds moult their feathers while at sea, which is an energetically costly behaviour. Mortality rates during moult can be high, so spatial and trophic ecology during this critical period is important for understanding demographic patterns. Unfortunately, individual foraging behaviours specifically linked to at-sea moulting are commonly unclear. This paper combines 2 different approaches to geolocation: data from bird-borne geolocation loggers and stable-isotope assignment using carbon and nitrogen isotope maps (isoscapes). Coupling 2 geolocation processes allows some uncertainties associated with isotope-based assignment to be constrained. We applied this approach to quantify species-specific foraging locations and individual trophic variability during feather regrowth in 3 sympatric auk populations breeding on the Isle of May, Scotland (common guillemot Uria aalge, razorbill Alca torda and Atlantic puffin Fratercula arctica). Inferred foraging areas during moult differed between species and feather types. Guillemots likely underwent moult within the southern North Sea, razorbills along the east coast of England and into the southern North Sea and puffins off the east coast of Scotland. Estimates of individual trophic position varied considerably within feather types (up to 1 trophic level difference between individuals), among feather types grown during different time periods and across the 3 species, with guillemots consistently foraging at higher trophic positions than razorbills and puffins. Used in combination, these methods better constrain foraging areas during moulting, and provide a technique to explore individual differences and flexibility in foraging strategy, which is valuable information for both seabird conservation and marine spatial planning.

KEY WORDS: Isoscape · Trophic ecology · Foraging · Moult · Atlantic puffin · Common guillemot · Razorbill

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Cite this article as: St John Glew K, Wanless S, Harris MP, Daunt F, Erikstad KE, Strøm H, Trueman CN (2018) Moult location and diet of auks in the North Sea inferred from coupled light-based and isotope-based geolocation. Mar Ecol Prog Ser 599:239-251.

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