Seasonal differences in at-sea activity of seabirds underline high energetic demands during the breeding period

Nele Markones (1) , Volker Dierschke (1) , Stefan Garthe (1)

1 Research and Technology Centre (FTZ)

We assessed seasonal differences in at-sea activity of Lesser Black-backed Gulls , Black-legged Kittiwakes and Common Guillemots in the south-eastern North Sea. The three species correspond to different ecological groups, with Lesser Black-backed Gulls representing omnivorous generalists, Kittiwakes representing surface-feeding pelagic seabirds, and Guillemots representing pursuit-diving pelagic seabirds. Using data from aerial surveys, we differentiated between active (flying or scavenging at fishing vessels) and inactive behaviour (swimming). We estimated the activity budgets of all three species for the different seasons and tested for differences in activity between different seasons. All species exhibited significant seasonal differences in activity, with the highest levels of activity observed during the breeding season. Numbers of flying auks were, however, exceptionally low in autumn due to moult and guarding of not-yet fledged chicks at sea. Our results underline the high energetic demands of the breeding season that lead to increased foraging and travelling activity.

Mots clés: Black-legged Kittiwake; Lesser Black-backed Gull; Common Guillemot; At-sea activity; Time–activity budget; Seasonality

Nele Markones, Volker Dierschke, Stefan Garthe. Seasonal differences in at-sea activity of seabirds underline high energetic demands during the breeding period. Journal für Ornithologie = Journal of Ornithology, 2009, 151 (2), pp.329-336. ⟨10.1007/s10336-009-0459-2⟩. ⟨hal-00568354⟩