Light loggers and stable isotopes contribute to identify moult locations

Most seabirds moult feathers outside the breeding season when they are at sea. Moulting is a very energy-demanding process, which can result in high mortality rates. During feather moult, the auks are flightless, making them particularly vulnerable to changes in the environment. It is therefore important to acquire knowledge about the auks’ spatial and trophic ecology during this process. In this study, researchers used data from bird-borne light loggers and stable isotope analyses. Coupling these two types of data enabled a quantification of species-specific foraging locations and individual trophic variability during feather moult in three auk populations breeding on the Isle of May, Scotland – common guillemots, razorbills and Atlantic puffins.

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

The study shows that inferred foraging areas during moult varied between species but also depended on the types of feather analyzed. Puffins likely remained off the east coast of Scotland, razorbills along the east coast of England and into the southern North Sea and guillemots within the southern North Sea.