:SEAav5 (2021) - DOI: https://doi.org/10.3354/meps13697
ADVANCE VIEWTwilight foraging enables European shags to survive the winter across their latitudinal range
Børge Moe1,2,*,#, Francis Daunt3,#, Vegard Sandøy Bråthen1, Robert T. Barrett4, Manuel Ballesteros5, Oskar Bjørnstad6, Maria I. Bogdanova3, Nina Dehnhard1, Kjell Einar Erikstad5,7, Arne Follestad1, Sindri Gíslason8, Gunnar Thor Hallgrimsson9, Svein-Håkon Lorentsen1, Mark Newell3, Aevar Petersen10, Richard A. Phillips11, Sunna Björk Ragnarsdóttir8,12, Tone Kristin Reiertsen5, Jens Åström1, Sarah Wanless3, Tycho Anker-Nilssen1
#These authors contributed equally to this work
ABSTRACT: Species breeding at high latitudes face a significant challenge of surviving the winter. Such conditions are particularly severe for diurnal marine endotherms such as seabirds. A critical question is therefore what behavioural strategies such species adopt to maximise survival probability. We tested 3 hypotheses: (1) they migrate to lower latitudes to exploit longer day length (‘sun-chasing’), (2) they forage at night (‘night-feeding’), or (3) they target high-quality food patches to minimise foraging time (‘feasting’). We studied the winter migration and foraging strategies of European shags Phalacrocorax aristotelis from 6 colonies across a latitudinal gradient from temperate regions to north of the Arctic Circle using geolocators deployed over 11 winters. We found evidence for ‘sun-chasing’, whereby average southerly movements were greatest from colonies at higher latitudes. However, a proportion of individuals from higher latitudes remained resident in winter and, in the absence of daylight, they foraged during twilight and only very occasionally during the night. At lower latitudes, there was little evidence that individuals migrated south, nocturnal feeding was absent, and twilight feeding was infrequent, suggesting that there was sufficient daylight in winter. There was no evidence that winter foraging time was lowest at higher latitudes, as predicted by the ‘feasting’ hypothesis. Our results suggest that shags adopt different behavioural strategies to survive the winter across their latitudinal range, dictated by the differing light constraints. Our study highlights the value of multi-colony studies in testing key hypotheses to explain population persistence in seabird species that occur over large latitudinal ranges.
KEY WORDS: Winter ecology · Phalacrocorax aristotelis · Partial migration · Latitudinal gradient · Foraging effort · Geolocation · Data logger
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Full text in pdf format  Supplementary material | Cite this article as: Moe B, Daunt F, Bråthen VS, Barrett RT and others (2021) Twilight foraging enables European shags to survive the winter across their latitudinal range. Mar Ecol Prog Ser :SEAav5. https://doi.org/10.3354/meps13697 Export citation Share: Facebook - - linkedIn |
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