How do seabird migrations differ from other bird migrations? An assessment on six pelagic species of the North Atlantic

Abstract

**Abstract:** Bird migration is commonly defined as a seasonal movement between breeding and wintering grounds. It is generally assumed to involve relatively straight and directed movement stretches, often with a latitudinal change, and characteristic daily activity patterns comprising less or no foraging and more traveling time. In addition, the spatial scale of movement is one order of magnitude larger during migratory stretches than during stationary periods. Here, our main objective was to test how well those statements apply to seabirds. Our first goal was to separate migratory stretches from stationary periods. Based on this characterization of the movements during the wintering period, our second goal was to compare the migration tactics between species and colonies. To this end, we used an extensive light-logger geolocator-based positional dataset on six pelagic seabird species (northern fulmar, common guillemot, Brünnich's guillemot, little auk, Atlantic puffin, black-legged kittiwake) from 29 colonies of the North-East Atlantic and several years, tracked as part of the SEATRACK project. Migratory stretches were identified based on track characteristics (movement rate, latitude, longitude). Additionally, we used the data obtained from conductivity sensors integrated to each light-logger to infer time spent flying, and when possible resting and foraging. During the non-breeding season, the six species had, on average, three to four migratory stretches and two to three distinct stationary periods. On average, tracked individuals spent the winter at lower latitudes than their breeding sites and followed specific migration routes rather than non-directionally dispersing from their colonies. Differences in daily activity patterns were small between migratory and stationary periods, suggesting that all species continued to forage and rest while migrating. Such a migratory strategy can be qualified as a "fly-and-forage". Our results show the importance of habitats visited during seabird migrations. Those habitats are not just flown over, but may be important for re-fuelling. **Authors:** Françoise Amélineau¹, Benjamin Merkel¹, Arnaud Tarroux², Sébastien Descamps¹, Tycho Anker-Nilssen², Oskar Bjørnstad³, Vegard Bråthen², Olivier Chastel⁴, Signe Christensen-Dalsgaard², Johannis Danielsen⁵, Francis Daunt⁶, Nina Dehnhard², Morten Ekker⁷, Kjell Einar Erikstad², Alexey Ezhov⁸, Per Fauchald², Maria Gavrilo⁹, Gunnar Hallgrímsson¹⁰, Erpur Hansen¹¹, Mike Harris¹², Morten Helberg¹³, Hálfdán Helgason¹⁴, Malin Johansen¹, Jon Jónsson¹⁵, Yann Kolbeinsson¹⁶, Yuri Krasnov⁸, Magdalene Langset², Svein-Håkon Lorentsen², Erlend Lorentzen¹, Mikhail Melnikov¹⁷, Børge Moe², Mark Newell¹², Bergur Olsen⁵, Tone Reiertsen², Geir Systad², Paul Thompson¹⁸, Thorkell Thorarinsson¹⁹, Ekaterina Tolmacheva²⁰, Sarah Wanless¹², Katarzyna Wojczulanis-Jakubas²¹, Jens Åström², Hallvard Strøm¹ ¹Norwegian Polar Institute, ²Norwegian Institute for Nature Research, ³Karmøy Ringmerkingsgruppe, ⁴Centre d'Etudes Biologiques de Chizé. CNRS-Université de La Rochelle, ⁵Faroe Marine Research Institute, ⁶Centre for Ecology & Hydrology, ⁷Norwegian Environmental Agency, ⁸Murmansk Marine Biological Institute, ⁹National Park Russian Arctic/Association Maritime Heritage, ¹⁰Faculty of Life and Environmental Sciences, University of Iceland, ¹¹South Iceland Nature Centre, ¹²UK Centre for Ecology & Hydrology, ¹³University of Oslo, ¹⁴Náttúrustofa Austurlands, East Iceland Nature Research Centre, ¹⁵University of Iceland?s Research Centre at Snæfellsnes, ¹⁶Northeast Iceland Nature Research Centre, ¹⁷Lipetsk State Pedagogical University, ¹⁸University of Aberdeen, ¹⁹Northeast Iceland Nature Research Center, ²⁰Kandalaksha State Nature Reserve, ²¹University of Gdansk