United States

**Abstract:**

Climate change and wide-scale environmental shifts are modifying oceanic patterns, sea ice phenology and abundance, ultimately with implications on food web dynamics. These changes alter the abundance and distribution of primary producers such as ice algae and phytoplankton, with cascading effects at higher trophic levels. Mercury (Hg) is an endocrine disrupting compound that biomagnifies in animals as a result of prey choice. As such, uptake is affected by altered food web dynamics and environmental conditions, which adds an important risk-based dimension in studies of foraging ecology. Multidimensional niche dynamics (δ13C, δ15N, THg; total mercury) were determined among female common eiders (Somateria mollissima) from 10 breeding colonies in areas within North America, Europe, and Russia. Results showed high variation in colony niche dynamics, indicated by niche size and ranges in δ13C, δ15N and THg values in relation to sea-ice presence and colony migratory status. Colonies with higher sea-ice cover during the pre-incubation period had higher median colony δ13C, δ15N and THg. Individuals at migratory colonies had relatively higher THg and δ15N, as well as lower δ13C, suggesting a greater Hg exposure, higher trophic position, and a greater reliance on phytoplankton-based prey. We concluded that variation in multidimensional niche dynamics exists amongst eider colonies which influenced THg concentrations. Further exploration of spatial ecotoxicology and niche dynamics at individual colonies is important to examine the relationships between anthropogenic pressures, foraging behaviour, and the related risks of contaminant exposure at even low concentrations which cumulatively may contribute to negative effects on population stability. Overall, multidimensional niche analysis that incorporates multiple isotopic and contaminant metrics presents an opportunity to help identify populations at risk to rapidly altered food web dynamics.

**Authors:**

Reyd Smith¹, David Yurkowski², Kyle Parkinson¹, Jérôme Fort³, Holly Hennin⁴, H. Grant Gilchrist⁴, Oliver Love¹

¹University of Windsor, ²Fisheries and Oceans Canada, ³Littoral, Environnement et Sociétés (LIENSs), ⁴Environment and Climate Change Canada

3rd World Seabird Conference

Environmental and life-history factors influence multidimensional niche metrics (δ13C, δ15N, Hg)

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!

symposium

**Abstract:**

In the past few decades much has been learned about the effects of oil on marine ecosystems. Specifically, the Exxon-Valdez oil spill in Alaska in 1989, the Treasure oil spill in South Africa in 2000, and most recently the Deepwater Horizon spill in the Gulf of Mexico in 2010, have led to an increase in studies that have examined the effects of oil on marine ecosystems, from invertebrates to birds. Currently in the Canadian Arctic there are low levels of shipping and oil exploration-related activities as compared to many other regions globally. While current levels of shipping and other oil-related activities may be low, there are natural oil and gas seeps in the region that expose seabird to oil-related contaminants. Importantly, there are several new biochemical/molecular techniques being used in effects studies in relation to oil. We present data on oil-related contaminants in two Arctic seabird species (the think-billed murre and the black guillemot) in relation to toxicogenomic and metabolomics tools that can identify sub-lethal effects from oil exposure. This information serves as baseline information for the region, as well as a tool that can be applied throughout these species' ranges to understand how oil pollution may affect the physiology of individuals.

**Authors:**

Jennifer Provencher¹, Mark Mallory², Bruce Pauli³, Phil Thomas³, Doug Crump³, Sarma Sailendra³, Yasmeen Zahaby³

¹ECCC, ²Acadia University, ³Environment and Climate Change Canada

Using toxicogenomic tools to detect effects of oil-related contaminants in seabirds

**Abstract:**

Seabirds are amongst the most threatened birds in the world, and incidental mortality (bycatch) in fisheries is one of the primary causes of population declines of large petrels. Albatrosses are particularly vulnerable given their life histories and because they are so wide-ranging, travelling hundreds to thousands of kilometres, and potentially encountering multiple threats in national and international waters. They are also attracted in very large numbers to fishing vessels to feed on offal or bait. Assessing their susceptibility to bycatch is essential for effective management and conservation. Wandering albatrosses at South Georgia have declined catastrophically since the 1960s, leading to the Government of South Georgia and the South Sandwich Islands-led Action Plan, and their listing as one of nine global priority populations by the Agreement on the Conservation of Albatrosses and Petrels (ACAP). Limited vessel-based monitoring indicate two areas of particularly high risk for wandering albatrosses; the Patagonian Shelf and Subtropical Convergence. Using novel radar-detecting loggers, we investigate the interactions of tracked wandering albatrosses with vessels in the South Atlantic. We quantify response distance and time spent following vessels during foraging trips, to map bycatch risk. This indicates where, when and from which fleets bycatch risk is greatest for wandering albatrosses, and greatly improves on previous coarse-scale analysis of overlap with fishing effort, to clearly identify areas and periods of highest susceptibility to bycatch.

**Authors:**

Ana Bertoldi Carneiro¹, Maria P. Dias, Steffen Oppel, Elizabeth Pearmain¹, Bethany L Clark, Andrew Wood², Tyler Clavelle, Richard Phillips²

¹BirdLife International, ²British Antarctic Survey

Fine scale seabird foraging behaviour in relation to fisheries

**Abstract:**

Sabine's gulls undertake the longest migration of any gull, a trans-equatorial journey between Arctic breeding and southern hemisphere wintering areas. For such long-distance migrants, quantifying within- and between-individual variation in migratory strategy is key towards understanding resilience to environmental variability encountered over migration. We tracked 22 birds on 32 migrations from the Canadian Arctic to evaluate strategies and quantify flexibility among individuals and years. All birds undertook extended stopovers in a geographically-restricted staging area halfway through migration in the California Current System in both directions. Individuals were otherwise flexible in most aspects of migration but were repeatable in arrival date and duration of the southbound staging phase. Routes taken during southbound migration and overlap in overwintering areas were significantly larger within the same year than among years. Overall, birds showed high individual flexibility in migratory strategies but made similar decisions to one another in the same years. Every year, all birds showed repeatable, consistent reliance on the staging grounds as a key stopover site in both directions. This suggests Sabine?s gulls adjust to environmental change in many aspects of their migration but may be vulnerable to climate change and other anthropogenic influences during critical stages of the journey.

**Authors:**

Sarah Gutowsky¹, Mark Mallory¹, Shanti Davis², Mark Maftei²

¹Acadia University, ²High Arctic Gull Research Group

Flexibility in migratory strategy contrasts with reliance on restricted staging and overwintering grounds for Sabine's gulls from the Canadian High Arctic

**Abstract:**

Sexual competition is increasingly recognized as an important selective pressure driving species distributions. However, few studies have investigated the relative importance of interpopulation versus intrapopulation competition in relation to habitat availability and selection. To explain spatial segregation between sexes that often occurs in seabirds, two hypotheses are commonly used. The 'competitive exclusion' hypothesis states that dominant individuals should exclude subordinate individuals through direct competition, whereas the 'niche divergence' hypothesis states that segregation occurs due to past competition and habitat specialization. We tested these hypotheses in two populations of an extreme wide-ranging and sexually dimorphic seabird, investigating the relative role of intrapopulation and interpopulation competition in influencing sex­ specific distribution and habitat preferences. Using GPS loggers, we tracked 192 wandering albatrosses Diomedea exulans during four consecutive years (2016-2019), from two neighbouring populations in the Southern Ocean (Prince Edward and Crozet archipelagos). We simulated pseudo-tracks to create a null spatial distribution and used Kernel Density Estimates (KDE) and Resource Selection Functions (RSF) to distinguish the relative importance of within versus between population competition. Kernel Density Estimates showed that only intrapopulation sexual segregation was significant for each monitoring year, and that tracks between the two colonies resulted in greater overlap than expected from the null distribution, especially for the females. RSF confirmed these results and highlighted key at­sea foraging areas, even if the estimated of at-sea densities were extremely low. These differences in selected areas between sites and sexes were, however, associated with high interannual variability in habitat preferences, with no clear specific preferences per site and sex. Our results suggest that even with low at-sea population densities, historic intrapopulation competition in wide ­ranging seabirds may have led to sexual dimorphism and niche specialization, favouring the 'niche divergence' hypothesis. In this study, we provide a protocol to study competition within as well as between populations of central place foragers. This is relevant for understanding their distribution patterns and population regulation, which could potentially improve management of threatened populations.

**Authors:**

Florian Orgeret¹, Ryan Reisinger², Tegan Carpenter-Kling¹, Alexandre Corbeau³, Danielle Keys¹, Charles-André Bost⁴, Henri Weimerskirch⁴, Pierre Pistorius¹

¹Nelson Mandela University, ²Institute of Marine Sciences, University of California Santa Cruz, ³Centre d'Etudes Biologiques de Chize, ⁴Centre d?Etudes Biologiques de Chizé

Spatial segregation in a sexually dimorphic central place forager: Competitive exclusion or niche divergence?

**Abstract:**

Wildlife are exposed to many simultaneous stressors, the effects of which are amplified along with increasing human activity globally. In Arctic regions, more severe weather systems, increasing air and ocean temperatures, and exposure to environmental contaminants all represent stressors occurring simultaneously. While seabirds are expected to be at risk of adverse effects from these individual stressors, few studies have researched their combined impacts on breeding behaviour and reproductive success. Therefore, we examined the interactive effects of air temperature, wind speed and mercury (Hg) contamination (via first-laid egg) on laying phenology and incubation behaviour in female common eiders (Somateria mollissima, Mitiq) nesting at Canada's largest Arctic breeding colony (East Bay (Mitivik) Island) from 2016-2019. Exposure to higher pre-breeding air temperatures resulted in females with higher egg Hg concentrations laying earlier than those with lower Hg levels. Furthermore, examination of 190 days of incubation behaviour from 61 eiders across two years showed that nest-level air temperature exposure had the most significant effect on incubation behaviour, with higher air temperatures correlating with more interruptions. Importantly, interactive exposure to higher air temperatures and higher Hg concentrations was related to increased incubation interruptions at a greater effect level than just air temperature alone. Although previous research has shown that warmer spring temperatures may relieve constraints on lower quality females, giving them more time to gain in body condition to successfully lay, our results suggest these females face stronger cumulative costs during incubation in warmer years, especially if they have higher contaminant loads. Our study highlights the potential interactive mechanisms, driven by human-induced environmental changes, that may impact overall individual and colony reproductive success in Arctic seabirds, especially within the context of increasing environmental and predator pressures.

**Authors:**

Reyd Smith¹, Saya Albonaimi¹, Holly Hennin², Grant Gilchrist², Jérôme Fort³, Kyle Parkinson¹, Jennifer Provencher², Oliver Love¹

¹University of Windsor, ²Environment and Climate Change Canada, ³Littoral, Environnement et Sociétés (LIENSs)

Cumulative effects of environmental conditions and mercury exposure on laying phenology and incubation behaviour

**Abstract:**

Timing of breeding is a trait shaped to optimize resource use while avoiding adverse conditions. It has been suggested that, in some seabird species, allochronic breeding between summer and winter populations may drive genetic isolation to different extents. However, little is known about the connectivity and ecological segregation between populations fuelling this evolutionary process. This study describes the phenology, connectivity, differences in spatial use, habitat selection, daily activity patterns, and isotopic niche of allochronic populations of the Cape Verde storm-petrel Hydrobates jabejabe breeding in Cima Islet Cabo Verde. We ringed breeders and birds in mist-nets for doing analyses on the populations connectivity, deployed GPS and GLS loggers for studying spatial niche in the breeding and non-breeding season respectively, and for studying the daily activity niche through wet-dry data, and took blood/feather samples for studying the isotopic niche. Summer (hot) population bred from February to August, while the winter (cool) population did it from September to January, showing a very low exchange rate of breeders between them and only a few inter-seasonal breeders. Both populations showed a high spatial overlap in their foraging areas during both, the breeding and the non-breeding period, respectively. Both populations fitted their timing of breeding to pulses of oceanic productivity around Cabo Verde while avoiding rainfalls, suggesting inter-seasonal breeders may be disfavoured. Oceanic productivity was higher for the hot population during the breeding and non-breeding areas and spent a higher proportion of time resting on the water during the non-breeding period. Overall, our results showed two populations well-differentiated in their annual phenological events and very low connectivity among them, but with little ecological segregation. Pulses of oceanic productivity may be driving allochrony but does seem not imply an speciation process.

**Authors:**

Fernando Medrano¹, Teresa Militão¹, Ivandra Gomes², Mariona Sarda-Serra¹, Monica de la Fuente¹, Herculano Dinis², Jacob González-Solis¹

¹Institut de Recerca de la Biodiversitat (IRBio) i Departament de Biologia Evolutiva, Ecologia i Cièn, ²Associação Projecto Vitó, São Filipe, Ilha do Fogo, Cabo Verde

Phenological divergence, population connectivity and ecological segregation between two allochronic seabird populations

**Abstract:**

Bird species that practice obligate siblicide (originally named cainism) lay two eggs, but almost never raise more than one offspring, because the first hatched chick kills the second soon after hatching. The adaptive value of this behavior has puzzled naturalists since the times of Aristoteles. There is still no general satisfactory explanation for the evolution of this behavior, although various mechanisms have been proposed. According to the "Insurance hypothesis", by laying an extra egg, the parents may be able to protect themselves from raising an under-sized brood (or no young at all) in a given season; specifically, they are buffered against complete reproductive failure that may arise from early mortality of eggs and chicks. This study aimed to test the "Insurance hypothesis" for the laying of a second egg. We experimentally tested this hypothesis in pairs of adjacent 2-egg clutches in a colony of breeding brown boobies (Sula leucogaster), by removing one egg from experimental clutches while holding unmanipulated clutches as controls. As predicted, the experimental nests on average produced fewer hatchlings and a smaller proportion of them had a chick at 10days, i.e. 34% and 61% for experimentals and controls, respectively. This difference was almost three-fold difference at 60 days post-hatching, i.e. 12% of experimental nests vs 31% of control nests produced a fledgling. The insurance benefit of the second egg seemed to be most significant during the incubation phase, or for fertilization of the eggs, because there was no difference in success between parents that had hatched one versus two eggs among unmanipulated clutches. However, among nests that were deserted during chick rearing, parents that had hatched two eggs tended to remain longer than parents that had hatched only one egg. We conclude that the most important insurance benefit of a second egg is against egg hatching failure.

**Authors:**

Lars Hillström¹, Francisco Sanchez Tortosa²

¹University of Gävle, ²University of Cordoba

Function of obligate siblicide in the Brown booby, Sula leucogaster: an experimental test of the Insurance hypothesis.

**Abstract:**

While most bird species exhibit bi-parental care, with both parents adjusting theirs workload in respect to each other, still little is known of how this adjustment is achieved. Vocal communication has recently been pointed out as a potential mechanism of such parental care adjustment in songbirds, but remains poorly studied in seabirds. Here we examine the role of partners' vocal interactions in the parental care of a monogamous seabird, the Little Auk (Alle alle). Little Auks' breeding partners share their parental duties equally and in a coordinated manner; during the whole breeding period they frequently meet at the nest and vocalize together, which makes it a perfect system for studying the role of vocal communication in parental coordination. We investigate whether the temporal and acoustical structure of the partners' vocal interaction in the nest predict its output (relief or not of the incubating partner), and whether they are related to the duration of the previous and subsequent incubation bouts. Our results are the first attempt to answer such questions in seabirds, and we believe they will constitute a solid background for both examining the mechanisms regulating parental care and the importance of vocal communication between avian breeding partners.

**Authors:**

Marion Devogel¹, Antoine Grissot¹, Dorota Kidawa¹, Marcelo Araya-Salas², Katarzyna Wojczulanis-Jakubas¹

¹University of Gdansk, ²Universidad de San josé

Should I stay or should I go: Is vocal communication a key to coordinated parental care in a monogamous seabird, the Little Auk (Alle alle) ?

**Abstract:**

Human activity may significantly affect animal abundance, distribution and behaviour. In several regions of the world, human productive activities generally show a marked difference in intensity between week-days and week-end. For instance, fishing activity, which is known to affect seabird behaviour, may show lower intensity on the week-end. To assess whether such fishing schedule affects seabird activity, we analyzed daily foraging behaviour of three seabird species breeding in the Adriatic sea, an over-exploited Mediterranean region where trawlers activity is interdicted during week-end. We relied on GPS-data from two seagull species, the Mediterranean gull (Ichthyaetus melanocephalus) and the yellow-legged gull (Larus michahellis), which can forage both on land and at sea, and from the pelagic Scopoli´s shearwater (Calonectris diomedea). All birds were GPS-tagged during the breeding period. The daily proportion of GPS positions at-sea over all recorded positions was significantly lower on week-end compared to week-days in both seagull species. Location at sea were such rare on the week-end as to suggest a possible transfer of information at the colony on the current distribution of food resources. Moreover, we found individual differences in the reaction to the "week-end effect". On top of this, we found that the probability of foraging at sea for gulls was higher when rain was absent or light and wave motion was slight. As for seagulls, also the pelagic Scopoli´s shearwater changed foraging behaviour on week-end, showing a significant lower proportion of those behaviours which are known for other tubenose species to be related to foraging in association with fishing vessels (sinuous movements and floating) and a higher proportion of relocation movements compared to week-days. Overall, our results highlight the marked behavioural plasticity of seabird species and stress the complexity of relationship between seabirds and commercial fishing activity.

**Authors:**

Jacopo Cecere¹, Simona Imperio¹, Simone Pirrello¹, Riccardo Nardelli¹, Alessandro Andreotti¹, Fernando Spina¹, Lorenzo Serra¹

¹ISPRA

Seabird foraging behaviour changes on the week-end according to scheduled fishery activity in the Adriatic Sea

**Abstract:**

Temporal patterns of animal activity can be affected by both abiotic (e.g. temperature, wind) and biotic factors (e.g. spatial and temporal distribution of prey species, inter-specific competition). Despite the analysis of activity rhythms can reveal how species adapt to environmental changes, little is known about daily activity patterns in seabirds. We investigated the diel activity pattern of 196 Scopoli's shearwaters (Calonectris diomedea) fitted with GPS-loggers from 3 different Mediterranean breeding sites, namely Linosa island (Sicily Channel), Tremiti Archipelago (Adriatic Sea) and La Maddalena Archipelago (Tyrrhenian Sea), from 2008 to 2018. During both incubation and chick-rearing periods breeding shearwaters are central-place foragers, performing self-provisioning foraging trips that last up to 18 days, alternated, during the latter period, to short chick-provisioning foraging trips. Behavioural modes, assessed through EMbC, revealed that both intensive and extensive search were evenly distributed during the daily cycle, while floating behaviour was concentrated during the night and the central hours of the day, and relocation was most frequent in the few hours following dawn and preceding dusk. Accordingly, flying activity computed as the average speed between two GPS positions showed a bimodal pattern for all the 3 colonies. Yet, the temporal pattern of flying activity was significantly different among colonies, with birds from Linosa showing narrower peaks of activity. The observed differences cannot be explained by different twilight times among colonies, and are likely linked to fishery activity and/or variation in meteorological variables, the latter also explaining the differences between sexes. Indeed, as the breeding period proceeds, females show higher flying activity, likely due to their lower wing loading and the consequent better ability in exploiting winds. Differences were also found between short- and long-lasting foraging trips, suggesting that modulation of the daily activity in seabirds may represent a behavioural adaptation to a combination of food availability and environmental conditions.

**Authors:**

Simona Imperio¹, Davide Dominoni², Federico De Pascalis³, Carlo Catoni⁴, Giorgia Gaibani⁵, Diego Rubolini³, Jacopo Cecere¹

¹ISPRA, ²University of Glasgow, ³University of Milan, ⁴Ornis Italica, ⁵LIPU

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