United States

**Abstract:**

The winter period is an energetic bottle neck for seabirds, challenging them with increased energy requirements due to higher thermoregulatory costs, diminished food resources, higher frequency of extreme weather events and shorter day lengths. These effects vary across latitudinal gradients of environmental severity. A critical question is therefore how individuals at higher latitudes in the breeding range obtain sufficient food to survive the winter. Specifically, it is unclear the extent to which individuals, a) migrate to lower latitudes to exploit longer day length, b) forage at night, or c) target higher quality food patches to minimise foraging time. We studied the migration and foraging strategies of European shags from six colonies across a latitudinal gradient spanning the Arctic Circle using geolocator/immersion loggers deployed over eight different winters. This species is a good candidate to test these questions since it has wettable plumage which results in high foraging costs during winter. We found that a proportion of individuals from higher-latitude populations remained resident in winter. In the absence of daylight they foraged during twilight and occasionally also during the night. The remainder of the population migrated south, benefiting from the longer photoperiod. At lower latitudes, there was little evidence that individuals migrated south and nocturnal feeding was absent, suggesting that there was sufficient daylight in winter. For no population was there evidence that foraging time was lowest in winter, which would suggest that prey availability changes less than expected. Thus, our results suggest responses to environmental conditions vary with latitude, and that individuals from higher latitudes may migrate south or increase crepuscular or nocturnal foraging. Our results demonstrate the range of individual strategies that enables a species to survive and breed across a marked latitudinal gradient.

**Authors:**

Børge Moe¹, Francis Daunt², Vegard Bråthen¹, Robert Barrett³, Manuel Ballesteros¹, Oskar Bjørnstad⁴, Nina Dehnhard¹, Kjell Einar Erikstad¹, Arne Follestad¹, Sindri Gíslason⁵, Gunnar Thor Hallgrímsson⁶, Svein-Håkon Lorentsen¹, Aevar Petersen⁷, Richard Phillips⁸, Sunna Ragnarsdóttir⁹, Tone Kristin Reiertsen¹, Sarah Wanless², Tycho Anker-Nilssen¹

¹Norwegian Institute for Nature Research, ²Centre for Ecology &amp; Hydrology, ³UiT The Arctic University of Norway, ⁴Norsk Ornitologisk Forening, ⁵Southwest Iceland Nature Research Centre, ⁶University of Iceland, ⁷n/a, ⁸British Antarctic Survey, ⁹Icelandic Institute of Natural History

3rd World Seabird Conference

Multicolony tracking of European shags reveal a latitudinal gradient in non-breeding migration and foraging strategies

Welcome Seabirders!  

Welcome to Virtual World Seabird Conference 3 - vWSC3! Whether you are in your office or lab, at home, in a coffee shop or bar poaching some wifi, or at a remote field site or research vessel – we are very excited to welcome you to the third ever World Seabird Conference. 

We would like to thank ALL of you for being so patient as WSC3 was scheduled, postponed, rescheduled, revised to virtual, and scheduled again. Throughout all those iterations there was one message that remained perfectly clear – seabirders were eager to meet and share their science. If we could not meet in person then virtual it would have to be, but a 3rd WSC was something everyone wanted. That support and commitment helped the WSU Board of Directors and Member Societies sort through all of the challenges they faced to plan and hold this conference. 

The list of those that need to be thanked is long and, while we plan on recognizing many during the live closing plenary, it is important to do so here in writing as well. 

The Australasian Seabird Group was our Local Host for our plan to meet in Hobart, Tasmania. They invested substantial time and effort to find venues and plan events that we unfortunately were not able to visit. Nonetheless we appreciate their work on behalf of WSC3 and encourage all of you to thank them when you see their members in Gathertown or elsewhere during our virtual meeting. Their willingness to host created the initial excitement for WSC3 and without that our vWSC would not have been possible.

We also wish to thank the Science Program Committee, the Virtual Committee, and the Early Career Scientist Committee for their hard work planning the logistics, events, and schedule for vWSC3. These committees also had to deal with changing parameters and short timelines that made what is always a challenging task even more challenging. The Travel Awards Committee also invested time and effort in developing procedures for awarding travel funds that ultimately would not be implemented. 

Our ability to shift from an in-person to a virtual meeting, and to do so in a way that would be financially feasible, was due to the effective efforts of The International Fundraising Committee and to our financial sponsors. The IFC raised funds to support WSC3 and then, through the good relationships they built with sponsors, ensured we could re-envision how those funds could be used to support a virtual conference that would be affordable and high-quality.

We all owe the WSU Board of Directors and the Representatives of the Member Societies a great deal of thanks. They are the ones who manage the WSU and, for the past 18 months, have had to have a series of challenging meetings and conversations, have had to make a series of difficult choices, have had to do all of that while considering the short- and long-term health of WSU and the World Seabird Conferences, and did this while also managing their own challenges at their day jobs. We are grateful for their diligence, patience, foresight, and throughout all of the meetings, their collegiality. Also – a 6-year term is quite a commitment!

There would not be a WSC3 without a successful WSC1 and WSC2. Thanks go to the Pacific Seabird Group for their support of WSC1 in Victoria, Canada, and to the African Seabird Group for their support of WSC2 in Cape Town, South Africa. In each of these endeavors and for our current conference we were fortunate to work with a dependable and trustworthy partner in Podium Conferences. Michelle Smith and Marischal de Armond have become valued members of our team and have not only helped us plan conferences but have assisted and advised the WSU Chairs and Board on issues above and beyond conference planning. 

As we embark on our vWSC3 week we extend to all of you our thanks for showing up, for being patient, and most importantly for the work you do with seabirds. We are all part of a unique, global community that shares an interest, a fascination, and a passion for birds that make a living in our world’s oceans. We have advanced the science, conservation, and management of seabirds as well the ecosystems they inhabit. We are consistently impressed and motivated by the work you do. 

The WSU formed in 2010 because we saw the need for a global organization to address challenges at a global level. Over the past 11 years WSU has grown, adapted, and evolved to become the community that this week is making vWSC3 a reality. Enjoy the week, appreciate and support the friends and colleagues you have made in the community, and if you see us in a virtual hallway please stop and say hello! 

Thank you for the opportunity to serve all of you and the WSU over the past few years,

Nicholas Carlile, Interim Chair, WSU<br>
Patrick Jodice, 2nd Chair of the WSU<br><br>

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Join us for four days of science, networking and virtual engagement with delegates from around the world!

**Abstract:**

The winter period is an energetic bottle neck for seabirds, challenging them with increased energy requirements due to higher thermoregulatory costs, diminished food resources, higher frequency of extreme weather events and shorter day lengths. These effects vary across latitudinal gradients of environmental severity. A critical question is therefore how individuals at higher latitudes in the breeding range obtain sufficient food to survive the winter. Specifically, it is unclear the extent to which individuals, a) migrate to lower latitudes to exploit longer day length, b) forage at night, or c) target higher quality food patches to minimise foraging time. We studied the migration and foraging strategies of European shags from six colonies across a latitudinal gradient spanning the Arctic Circle using geolocator/immersion loggers deployed over eight different winters. This species is a good candidate to test these questions since it has wettable plumage which results in high foraging costs during winter. We found that a proportion of individuals from higher-latitude populations remained resident in winter. In the absence of daylight they foraged during twilight and occasionally also during the night. The remainder of the population migrated south, benefiting from the longer photoperiod. At lower latitudes, there was little evidence that individuals migrated south and nocturnal feeding was absent, suggesting that there was sufficient daylight in winter. For no population was there evidence that foraging time was lowest in winter, which would suggest that prey availability changes less than expected. Thus, our results suggest responses to environmental conditions vary with latitude, and that individuals from higher latitudes may migrate south or increase crepuscular or nocturnal foraging. Our results demonstrate the range of individual strategies that enables a species to survive and breed across a marked latitudinal gradient.

**Authors:**

Børge Moe¹, Francis Daunt², Vegard Bråthen¹, Robert Barrett³, Manuel Ballesteros¹, Oskar Bjørnstad⁴, Nina Dehnhard¹, Kjell Einar Erikstad¹, Arne Follestad¹, Sindri Gíslason⁵, Gunnar Thor Hallgrímsson⁶, Svein-Håkon Lorentsen¹, Aevar Petersen⁷, Richard Phillips⁸, Sunna Ragnarsdóttir⁹, Tone Kristin Reiertsen¹, Sarah Wanless², Tycho Anker-Nilssen¹

¹Norwegian Institute for Nature Research, ²Centre for Ecology & Hydrology, ³UiT The Arctic University of Norway, ⁴Norsk Ornitologisk Forening, ⁵Southwest Iceland Nature Research Centre, ⁶University of Iceland, ⁷n/a, ⁸British Antarctic Survey, ⁹Icelandic Institute of Natural History

symposium

**Abstract:**

Tidal-stream environments are characterised as areas of water motion that are turbulent along coastlines which produce predictable high current velocities in excess of 1 ms-1. Due to site-specific topography and bathymetry these environments produce complex motions of fluid, resulting in distinct features (boils, eddies, jets and shear lines), that vary across small spatio-temporal scales (<10 m and <1 min). Seabirds utilise these features, with it being theorised that they create periods of increased food availability, and foraging efficiency, due to aggregating or disorientating prey species. Current literature indicates a need to examine these turbulent environments at a higher spatial and temporal resolution. This is to increase the accuracy of habitat characterisation, uncover new drivers of top predator usage, and in doing so help to better inform on the potential ecological impacts of tidal-energy developments. Drones offer the ability to collect cost-effective datasets, which are suitable for the capture of fine-scale interactions occurring between seabirds and habitat features. With the advancement of sensory instrumentation, and the development of image processing techniques, we can also increase both the frequency and accuracy of these data. Drone imagery, previously collected from the MeyGen tidal energy site in the Pentland Firth in Scotland, will be used. This was gathered alongside continuous vessel-based surveys which collected active acoustic and observer data. An examination of fine-scale seabird distribution and behaviour (flying, loafing and diving), against a range of defined feature characteristics and existing tidal variables, will be undertaken. The image processing methods used to detail drone-derived, ecologically relevant, seabird and hydrodynamic data will be presented. Preliminary findings with regards to fine-scale seabird distribution and behaviour will also be displayed.

**Authors:**

James Slingsby¹, Benjamin Williamson¹, Louise Kregting², Jason McIlvenny¹, Jared Wilson³, Julien Martin⁴, Beth Scott⁵

¹University of the Highlands and Islands, ²Queen's University Belfast, ³Scottish Government, ⁴University of Ottawa, ⁵University of Aberdeen

Exploring fine-scale seabird usage of tidal-stream environments - Using drones as an ecological survey tool

**Abstract:**

Seabirds have increasingly encountered offshore wind farms (OWFs) in European waters in the past 10 years, resulting in potential conflicts with offshore foraging areas. During the breeding season, seabirds are restricted in their choice of foraging habitats and are under increased pressure to find enough prey to raise their offspring. However, information on the individual reactions of seabirds towards operating OWFs during the breeding season is largely lacking. Three OWFs located 23-35 km north of the island of Helgoland in the southern North Sea are operating since 2015. We studied their effects on locally breeding northern gannets, black-legged kittiwakes and common guillemots using GPS tracking between 2015 and 2017. GPS tags were deployed on 63 breeding individuals for 0.1-13.9 weeks. Most gannets and guillemots predominantly avoided OWFs. A point process modelling approach revealed a significantly reduced resource selection inside the OWFs compared to the surroundings for both species. OWF avoidance by guillemots was even stronger when turbine blades were rotating. Only few gannets frequently entered OWFs when foraging or commuting. Flight altitudes of gannets inside the OWFs were close to the rotor-blade zone, especially for individuals predominantly avoiding the OWFs and during commuting. Kittiwakes mainly avoided OWFs close to the colony but sometimes entered OWFs which were located in further distance to the colony. These results provide a detailed description of seabirds' reactions to OWFs during the breeding season, and one of the first comprehensive analyses of OWF effects on these species based on telemetry data. The documented effects need to be considered during the planning processes for future OWFs, especially for locations close to large seabird breeding colonies.

**Authors:**

Verena Peschko¹, Nele Markones¹, Bettina Mendel¹, Moritz Mercker², Stefan Garthe¹

¹University of Kiel, ²BIONUM

Telemetry reveals strong impacts of offshore wind farms on common guillemots and northern gannets and differing reactions of black-legged kittiwakes during the breeding season

**Abstract:**

Tidal streams are a developing source of renewable energy and an important foraging habitat for several species of seabird. The north of Scotland is host to the world's first array of tidal stream turbines, constructed within the Inner Sound of the Pentland Firth. Inshore diving seabirds such as black guillemots Cepphus grylle are known to associate with tidal currents and dive to depths at which tidal turbines will operate. Black guillemots were therefore highlighted as vulnerable to foraging habitat alterations caused by turbine deployment and are at potential risk to collision with turbine blades. However, the extent to which these devices will affect black guillemots is unknown due to a lack of more detailed knowledge regarding their foraging ecology. This study addresses this knowledge gap by using GPS tracking technology to identify spatial and temporal aspects of foraging behaviour and habitat use. Thirteen adult black guillemots were GPS tracked during the 2016 and 2017 breeding seasons from Stroma, Caithness, an island of interest due to its close proximity to the MeyGen tidal lease area within the Inner Sound. Individuals displayed clear preference for specific foraging locations, associating strongly outside or within tidal streams. The foraging behaviour of individuals using the tidal stream was found to be associated with a narrow range of tidal velocities and depths. Foraging locations are potentially related to hydrodynamic features forming within these conditions, which are thought to aggregate prey. The MeyGen lease area generally contained faster tidal velocities and deeper depths than those associated with foraging, leading to minimal direct overlap. This research highlights the characteristics of tidal streams with which black guillemots associate. Such knowledge is vital when predicting the impact of tidal turbine installations on marine wildlife through environmental or habitat alteration.

**Authors:**

Daniel Johnston¹, Robert Furness², Alexandra Robbins³, Glen Tyler¹, Elizabeth Masden⁴

¹British Trust for Ornithology, ²MacArthur Green Ltd, ³Scottish Natural Heritage, ⁴Environmental Research Institute

Investigating the foraging habitat of black guillemots in relation to tidal stream turbines

**Abstract:**

Marine renewables, including tidal energy devices, are increasingly being deployed across the world to mitigate climate change. However, there are concerns that marine wildlife will experience negative interactions with such devices, for instance through collisions or displacement. The UK holds ca. 50% of Europe's tidal energy resource and contains numerous tidal development sites yet is also home to internationally important seabird populations. In the face of over-fishing and climate change, additional pressure from stressors such as tidal turbines could be devastating. Therefore, to ensure sustainable deployment of tidal energy devices, there is a need to quantify any adverse effects on seabirds. Before effects can be assessed, suitable methods to do so need to be identified. We therefore developed a conceptual framework to aid in the choice of survey method(s) to gather data on seabird behaviour relevant to interactions with tidal energy devices. Following a literature review of available methods in the context of this framework we identified, amongst others, an opportunity for enhanced use of bird-borne biologging and telemetry (bio-tracking) data, as well as the need for research into close-range overlap and behaviour around turbines and the environmental variables underlying seabird use of tidal stream environments. Subsequently, we developed an analysis workflow for the use of bird-borne bio-tracking data in assessing spatial overlap with marine renewables and applied it to European shags (Phalacrocorax aristotelis) and tidal turbines in the Pentland Firth, Scotland. We found that at the current scale of tidal site leasing in the UK overlap was minimal (0.14%), however at the scale of future/planned development areas, overlap was very high (99.4%). Research into the importance of tidal velocity and bathymetry to use of tidal stream environments by diving seabirds will further clarify potential effects from tidal energy devices.

**Authors:**

Natalie Isaksson¹, Benjamin Williamson¹, Jonathan Houghton², Jared Wilson³, Elizabeth Masden¹

¹University of the Highlands and Islands, ²Queen's University Belfast, ³Marine Scotland Science

Seabird use of tidal stream environments and potential interactions with tidal energy devices

**Abstract:**

Assessing avian collision risk is a key part of the Environmental Impact Assessment (EIA) process for offshore wind farms. Whilst a number of collision risk models are available, these all typically combine an estimate of the probability of a bird which passes through a turbine's rotor sweep colliding with a blade and the number of birds passing through this collision risk window in any given time period (as estimated from pre-construction data). As the size and extent of offshore wind farms increase as part of attempts to reach net zero carbon emissions by 2050, accurately assessing collision risk in order to minimise any negative environmental impacts becomes a pressing concern. However, the simplistic assumptions made by these models in relation to the flight behaviour of the species concerned - speed, height and direction - have raised questions about how realistic predictions from these models are. A lack of validation of existing models further calls into question whether these are able to accurately assess collision risk. Tracking data are increasingly being used to investigate potential impacts of wind farms and offer the potential to more accurately describe the behaviour of birds within any given site. These data demonstrate how seabird behaviour varies spatially, highlighting that the summarised information used by many existing models may not accurately reflect spatial and temporal variation in collision risk. Using multi-year tracking data, we modelled the speed, flight height and distribution of lesser black-backed gulls in relation to operational offshore wind farms. We combined these data with real time estimates of turbine rotational speed and the height of the turbine rotor above sea-level in order to estimate collision risk over the course of a breeding season. We further discuss how combining tracking data with ongoing camera-radar studies of collision risk at operational wind farms offers the potential to validate estimates of collision risk and reduce uncertainty in the EIA process.

**Authors:**

Aonghais Cook¹, Chris Thaxter², Jennifer Border², Philipp Boersch-Supan², Elizabeth Humphreys³, Elizabeth Masden⁴, Niall Burton²

¹Dr, ²British Trust for Ornithology, ³British Trust for Ornithology Scotland, ⁴University of Highlands and Islands Environmental Research Institute

Using GPS tracking data to assess collision risk in an operational wind farm

**Abstract:**

Geolocator tracking of adult flesh-footed shearwaters from breeding colonies in Australia and New Zealand has shown that these adults travel northwards to either the coast of Japan or India (in the case of Western Australia populations) during their non-breeding period. However, there are numerous year-round sightings of flesh-footed shearwaters off the coast of North America; could this be where fledglings go? To gain more understanding of the at-sea movements and distribution of juvenile flesh-footed shearwaters, ten Geotrak Solar satellite tracking devices were deployed on fledglings from Ohinau Island on the Coromandel Peninsula, New Zealand. All ten fledged from the island, but one device never transmitted, and another only transmitted for a few 100 km before stopping. The remaining eight fledglings headed immediately northwards into the Pacific within 10 days of leaving Ohinau Island before slowing down and beginning to forage north of Fiji or east around Samoa and Tokelau. Once in this area, all devices stopped transmitting. Given all of the devices had good battery levels when they last transmitted, it is possible that all these flesh-footed shearwater juveniles were accidentally caught in commercial fisheries in this known high-intensity fishing region. However, despite the very secure attachment method, we cannot rule out that the fledglings did not just simply pull the devices off as the adults are prone to do, although this would be unusual as all the birds would have had to decide to do this at the same time and in the same at-sea region. This work shows the need for continued tracking of all age classes of flesh-footed shearwaters to further determine their distribution and behaviour at sea and importantly, the risk to this species from fishing.

**Authors:**

Patrick Crowe¹, Dan Burgin¹, Graeme Taylor², Igor Debski², Elizabeth Bell¹

¹Wildlife Management International Ltd, ²Department of Conservation

Ohinau Island to the Pacific and beyond - tracking flesh-footed shearwater fledglings

**Abstract:**

The rapidly changing climate in the Arctic is expected to have significant impacts on seabird foraging ecology, mediated through changes in the distribution and abundance of their prey but also the distribution of competitors (e.g. with southerly species expanding into the Arctic). Here we study how the environment and competition interactions affect the foraging ecology and abundance of two closely related species breeding in sympatry in several colonies around the Arctic: the common guillemot (a temperate species) and Brünnich's guillemot (an Arctic species). For this, we tracked the two species during the breeding season with GPS and temperature-depth recorders at five colonies around Iceland, which is surrounded by contrasted marine environments (due to different cold and warm currents). We relate the habitat use of the two species to available environmental conditions around each site and colony size. We then relate population counts and trends to surrounding temperature and competition. We find different foraging behaviours and different degrees of overlap between the two species among the different sites, but not always more pronounced segregation in the biggest colony. Nevertheless, even though we found evidence of segregation at most sites, we did not find any effect of competition at the population level.

**Authors:**

Anne-Sophie Bonnet-Lebrun¹, Jason Matthiopoulos², Þorkell Þórarinsson³, Yann Kolbeinsson³, Thomas Larsen⁴, Patrick Roberts⁴, Morten Frederiksen⁵, Aude Boutet¹, Derren Fox¹, Tim Morley¹, Kirsty Franklin⁶, Kayleigh Jones¹, Erpur Hansen⁷, Norman Ratcliffe¹

¹British Antarctic Survey, ²Institute of Biodiversity, Animal Health and Comparative Medicine, ³Northeast Iceland Nature Research Centre, ⁴Max Planck Institute for the Science of Human History, ⁵Aarhus University, ⁶University of East Anglia, ⁷South Iceland Nature Research Centre

Using multi-colony tracking to understand the foraging ecology of two sympatrically breeding auks around Iceland

**Abstract:**

Seabirds are highly mobile animals, flying vast distances across open oceans on a single foraging trip or a long migration journey. Identifying the drivers of seabird movements, and the fitness consequences of variation in these movements, is key to understanding the mechanisms shaping their ecology and ultimately to predict how their distribution and populations may be affected by environmental change. Multi-colony studies are a powerful tool to identify large-scale ecological drivers of seabird movement, measure variation between populations and understand how these may affect population dynamics. I illustrate this claim with three examples of multi-colony studies I have recently been leading, from a small-scale comparison of two populations to an ocean-wide study, all of which have yielded important ecological findings. First, studying the spatial ecology and breeding behaviour of two seemingly similar populations of tropicbirds in the Indian Ocean reveals stark differences between the two locations, suggesting underlying differences in environmental conditions and highlighting the need for distinct conservation approaches. Second, a larger-scale comparison of the foraging ecology of four colonies of Atlantic puffins in the UK, Iceland and Norway with different population trends and breeding performance helps us to identify drivers of population declines. Finally, a species-wide study of thirteen puffin colonies across the North Atlantic unveils key ecological drivers of migration.

**Authors:**

Annette Fayet¹

¹University of Oxford

Drivers of seabird movements and their fitness consequences: insights from multi-colony tracking

**Abstract:**

Migration is a widespread strategy for escaping unfavourable conditions during winter, but the extent to which populations that segregate during the breeding season aggregate during the non-breeding season is poorly understood. Whilst segregation may be associated with higher overall likelihood of overlap with threats, but fewer populations affected, aggregation may result in a lower probability of exposure to threats, but higher overall severity. We investigated non-breeding distributions and extent of population aggregation in two sympatrically breeding auks. We deployed geolocators-immersion loggers on common guillemots Uria aalge and razorbills Alca torda at eleven colonies around the north of the UK and tracked their movements across two non-breeding seasons (2017-18; 2018-19). Using 290 guillemot and 135 razorbill tracks, we mapped population distributions of each species and compared population aggregation during key periods of the non-breeding season: post-breeding moult and mid-winter, observing clear interspecific differences. Razorbills were largely distributed in the North Sea, whereas guillemot distributions were spread throughout Scottish coastal waters and the North, Norwegian and Barents Seas. We found high levels of aggregation in razorbills and a strong tendency for colony-specific distributions in guillemots. Therefore, razorbills are predicted to have a lower likelihood of exposure to marine threats, but more severe potential impact due to the larger number of colonies affected. This interspecific difference may result in divergent population trajectories, despite the species sharing protection at their breeding sites. We highlight the importance of taking whole-year distribution into account in spatial planning to adequately protect migratory species.

**Authors:**

Lila Buckingham¹, Maria Bogdanova¹, Jonathan Green², Bob Furness³, Francis Daunt¹

¹UK Centre for Ecology and Hydrology, ²University of Liverpool, ³MacArthur Green

Interspecific variation in non-breeding aggregation: a multi-colony tracking study of two sympatric seabirds

**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

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