United States

**Abstract:**

Duration of parental care in avian species varies widely, from altricial to precocial species. The seabird family Alcidae is unique among birds in their variation of mass and age of juveniles at nest departure. The common guillemot Uria aalge exhibits an intermediate nest departure, where the chick leaves the nest flightless and only at a quarter of adult body size. The aim of this study was to examine factors controlling chick growth and timing of nest departure. To assess this, we followed common guillemot families including mother, father and chick from hatching to post-departure. Both parents and chick were sampled as soon as possible after hatching and followed throughout the nestling period. At nest site, samples were taken of each parent in each family twice to assess baseline corticosterone (CORT) levels and body condition at the onset and the end chick rearing period. Chicks were monitored at nest site by measuring body condition at hatching (1-4 days), 15 days of age, and 20 and 25 days of age if chick was still at nest site. The topography of the study site made it possible to catch the chicks after they had jumped from the nest site. This provided us with unique measurements of body conditions on chick post-departure. We found a positive relationship between chick age at nest departure and maternal body condition around hatching, indicating that mothers in better condition could afford a longer chick rearing period. Both paternal and maternal baseline CORT-level and body condition influenced weight and wing-length of the chicks at departure. Indications of strong synchronized departure events during the evening hours were found: 30 of the 40 chicks followed in the present study, departed the colony in five evenings only. Moreover, the observed departure events were highly weather dependent: strong winds directed towards the colony were avoided.

**Authors:**

Malin Johansen¹, Tone Reiertsen², Susanne Jenni-Eiermann³, Nigel Yoccoz⁴, Kjell Einar Erikstad²

¹Norwegian Polar Institute, ²Norwegian Institute for Nature Research, ³Swiss Ornithological Institute, ⁴University of Tromsø - The Arctic University of Norway

3rd World Seabird Conference

Strategies for timing of nest departure in the common guillemot Uria aalge

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!

poster

**Abstract:**

Since historical times Peruvian boobies - Sula variegata - have been recognized as an important guano-producer seabird in Peru due to their large numbers and dense colonies. They are also major bio-indicators and target conservation species within the Marine Protected Areas in Peru. Nevertheless, there is no long-term ecological monitoring programs other than estimates of their population size. We used time-lapsed cameras installed on several islands and walled-off headlands of Peru between 2016 and 2019 to evaluate their feasibility and accuracy to determine some aspects of the breeding and foraging behavior of Peruvian boobies. Time-lapse cameras were programmed at 15-min intervals, lasting approximately 6 months. Feeding trip length of chick-rearing adults were accurately determined when contrasting presence/absence of dyed birds from the photographs with GPS tracks of the same birds (r²=0.98). Nest survival curves were determined and causes of nest failures were identified (e.g. tick infestation) or discarded (e.g.predation). Breeding phenology was also determined on different islands arriving to the conclusion that boobies are highly asynchronous both within and across colonies. Inter-annual variations on these parameters linked to oceanographic conditions and fishing activities would shed light for a better understanding of seabird number fluctuations and conservation.

**Authors:**

Carlos Zavalaga¹, Diego Ardiles¹, Cristina Burga¹, Diego Gonzales¹, Cinthia Irigoin-Lovera¹, Sebastián Lozano¹

¹Universidad Científica del Sur

Time-lapse cameras on guano islands of Peru: Reliable and accurate tools to determine breeding sucess, trip length and breeding phenology of Peruvian boobies

**Abstract:**

Penguins are common model organisms in basic and applied research on climate change, marine pollution, and fisheries management in Antarctica. For example, Adélie (Pygoscelis adeliae) and Chinstrap (P. antarctica) penguins are focal species in krill fisheries management efforts in the Southern Ocean because their diets contain high proportions of Antarctic krill (Euphausia superba) and their performance is assumed to be an indicator of ecosystem status. However, most studies of penguin foraging ecology have focused on the breeding season and little is known about these species' diets during the winter. Stable isotopes analysis can be used to infer seabird diets when they are away from their colonies, but often cannot distinguish the influence of a consumer's diet (i.e. what it eats) from geographic or temporal differences in baseline isotopic values (i.e. where and when it is eating). To address these challenges, we used compound-specific stable isotope analysis of amino acids in feathers to compare the breeding (i.e. chick rearing) and non-breeding (i.e. winter) trophic niches of Adélie and Chinstrap penguins from the South Shetland Islands, Antarctica while explicitly accounting for varying isotopic values at the base of the food web. We found that these species had similar trophic positions (~3.3) reflective of krill consumption during the chick rearing period similar to past studies using more traditional methods. However, trophic position was higher in Chinstrap penguins wintering in ice free areas (3.9), relative to Adélie penguins wintering in ice covered areas (3.1). Moreover, trophic position differed between Chinstrap penguins migrating eastward into the Scotia Sea (3.6) or westward to the Pacific sector of the Southern Ocean (4.0). These results suggest that estimates of Adélie and Chinstrap penguin diets and krill consumption from the breeding season may not be necessarily reflective of the trophic niches of these species year-round.

**Authors:**

Michael Polito¹, Katelyn Lamb¹, Jefferson Hinke²

¹Louisiana State University, ²National Oceanic and Atmospheric Administration

A Winter's Tail: Stable isotope analysis of feather amino acids identify contrasting seasonal trophic niches in Antarctic penguins with differing migration strategies

**Abstract:**

One of the highest goals in seabird life history studies is in detecting animal movements and life cycles without interfering with the animals' natural behaviour. This goal is most fully realised when animals are studied remotely, without ongoing exposure to human researchers, and without any external biologging device inhibiting their natural movement. Radio-frequency identification (RFID) offers opportunities to monitor seabirds that must return to a consistent location. Detections by fixed automated systems (antennas and weighbridges) provide the opportunity to collect ongoing, consistent data which can be used to estimate survival, dispersion, or to understand foraging patterns. On Phillip Island, Australia, we have operated weighbridge systems for over 20 years to monitor the local population of penguins. These systems have proved an extremely useful tool for our research both in the value of the data they produce, and the ability to greatly reduce the field work required to monitor the local population. Here, we propose the use of these systems to achieve similar results in remote locations. We will outline the fundamentals of the systems we have in place, and the requirements for implementing similar systems in other situations. We will specify the biggest challenges and limitations other researchers are likely to come across, and some of the solutions we have devised to overcome them. We will also outline some of the research outcomes we have been able to achieve thanks to the implementation of these weighbridge systems, particularly for detecting transitions between breeding stages. This relatively low cost system has the potential to be used in remote colonies, with robust methodologies, significant sample sizes, and minimal disturbance.

**Authors:**

Ross Holmberg¹, Kean Maizels², Richard Reina³, Andre Chiaradia¹

¹Phillip Island Nature Parks, ²Kean Electronics, ³Monash University

Weighbridges: remote monitoring with minimal disturbance

**Abstract:**

Understanding seabirds' diets is key in understanding species reactions to current and future marine ecosystem changes. Finding appropriate and practical methods for diet sampling and ensuring comparability between historical and current studies is therefore essential. We studied the diet of common guillemot (Uria aalge) chicks at the Baltic Sea island of Stora Karlsö ((57° N, 17° E)) using a multi-method approach, combining dawn-to-dusk feeding watch studies (2005-2019), stomach content analysis (2008-2020), and nest sampling of discarded prey (1972-1976 + 2015-2021). Local chick diet composition was previously based on secondary data: prey dropped in nests not verified to represent consumed prey, and ocular feeding observations not allowing for distinction between sprat (Sprattus sprattus) and herring (Clupea harengus). By collecting 200+ chicks (deceased by unsuccessful landing during fledging), stomach content could be analyzed. This material was then compared with dropped prey of the same period. The material from the two sources matched, confirming the usefulness of dropped fish as an indicator of consumed prey. This allowed for a historical comparison of dropped fish, showing both some change in prey species composition and in prey size between the 1970s and today. Monitoring diet change over time can inform about both local seabird conditions, and marine ecosystem changes at large, and is fundamental in prey based models. Climate change, fisheries, eutrophication and population dynamics in all trophic levels possibly effect seabird diet composition and by comparing historical and current trends more can be known about links in marine ecosystems.

**Authors:**

Per-Arvid Berglund¹

¹Baltic Seabird Project

A multi-method approach to monitor and categorize changes in diet composition in common guillemots in the Baltic Sea

**Abstract:**

Understanding how both quality and quantity of prey affect the population dynamics of marine predators is a crucial step toward predicting the effects of environmental perturbations on population-level processes. The Junk Food Hypothesis, which posits that energetic content of prey species may influence reproductive capacity of marine top predators regardless of prey availability, has been proposed as a mechanism by which changes in prey populations could affect predator populations in high latitude systems; however, support for this hypothesis has been inconsistent across studies, and further data are needed to elucidate variation in the relative importance of prey quantity and quality among predator species and across ecological systems. We tested the relative importance of prey quantity and quality to nestling survival, condition, and stress levels in the eastern brown pelican (Pelecanus occidentalis carolinensis) across 9 breeding colonies in the northern Gulf of Mexico. Compared to previous results from cold-water systems, we found lower and less variable energy densities (4.4 kJ g−1, vs. 5.2 to 6.5 kJ g−1 in other studies) and lipid content (9% dry mass, vs. 16 to 23% in other studies) of common prey items. As a result, energy density of meals was not a strong predictor of fledging success, body condition, or stress levels of nestlings. However, both feeding frequency and meal mass were significantly correlated to energy provisioning rates and nestling survival. We also found that levels of the stress hormone corticosterone in nestling feathers collected at 3-4 weeks of age correlated strongly with provisioning rates and predicted both pre-and post-fledging survival more effectively than did one-time measures of body condition. We conclude that quantity rather than quality of prey, particularly small schooling fish, is the main driver of brown pelican reproductive success in this system, and that environmental perturbations affecting biomass, distribution, and abundance of forage fish could substantially affect brown pelican reproductive success. Moreover, our results suggest that feather corticosterone can provide information on both nutritional stress and survival rates in free-living seabird nestlings.

**Authors:**

Juliet Lamb¹, Yvan Satge², Katie O'Reilly³, Patrick Jodice⁴

¹University of Rhode Island, ²Clemson University, ³University of Portland, ⁴US Geological Survey

Diet composition and provisioning rates of nestlings determine reproductive success in a subtropical seabird

**Abstract:**

Social aggregations of chicks often occur in avian species with precocial young. Chicks are left alone for periods of time by both parents while they forage, and may or may not be guarded by other parents feeding their own chicks. The benefits of chick aggregations are thought to include reduced predation, increased thermoregulation, and social information transfer but few studies have examined the effects of sociality on chick survivorship. Our study investigated variation in chick sociality in a colonial seabird, the sooty tern Onychoprion fuscatus on Accession Island, South Atlantic. The number of chick associates (or 'friends') varied with chick age, at first increasing with age and then declining as fledging approached. Our results indicate that social group size may be a response to predation pressures during a period of increased vulnerability related to developmental stage. This has conservation management implications in terms of the need for introduced predator control together with further understanding of the predation rates by endemic Ascension Frigatebirds Fregata aquila. Our study highlights the importance of the accountability of offspring social connectivity as a driver of population-level breeding performance in demographic studies of species with socially aggregating young.

**Authors:**

Jonathon Sadler¹, John Colbourne¹, Roger Dickey², Sam Weber³, Adriana Maldonado-Chapirro¹, James Reynolds¹

¹University of Birmingham, ²Land Forces Directorate, ³Ascension Island Government

Friends with benefits: The importance of chick sociality for survivorship in a precocial seabird

**Abstract:**

Little is known about sleep and vigilance in terns despite nocturnal predators causing widespread breeding failure. In a 2013-2018 study of two North American Common Tern breeding colonies, we found surprisingly large differences in sleep duration and vigilance that we hypothesized were due to long-term predation risk (e.g., 64% of night with eyes open at the high-risk site versus 17% at the low-risk site). Here, to tease out the effects of predation from other colony-specific differences, we take advantage of a natural experiment in 2019 (when predation pressure was reversed) and expand this work to include diurnal sleep patterns. We recorded sex-specific sleep and vigilance behaviors during incubation for marked adults at both sites using 1-min time-lapse photographs taken throughout 48-h periods for 19 nests. In 2020, we investigated evidence for compensatory sleep at roosts and in 2021 we used time-lapse video to explore fine-scale sleep behavior. The presence of active predators at the low-risk site reduced the sleep of terns three-fold, but there were no diurnal differences in sleep between sites or sexes. Sexes distributed nocturnal incubation evenly and were equally vigilant, but at the high-risk site only one partner was ever present at night, even on nights when predation was not evident. Sleep at roosts was uncommon and reduced on nights when predators were present. In 2019, incubating terns at the high-risk site were never observed in deep sleep, and at the low-risk site terns entered deep sleep for <70 min on average. There was no evidence for compensation by sleeping during the day or at roosts. Thus, nest predators caused substantial reductions in sleep. While research on other taxa suggests that some birds may accommodate periods of sleep deprivation during migration, the physiological and fitness consequences of predator-induced sleep reduction during breeding have yet to be explored.

**Authors:**

Jennifer Arnold¹, Stephen Oswald¹, Paul Curtis², Ryan Hartman¹, Emily Case¹, Alexis Albu¹, Devin Tipton¹

¹Penn State University, Berks Campus, ²Cornell University

To Sleep or Not to Sleep? Effects of nocturnal predators and predation risk on sleep behavior in incubating Common Terns (Sterna hirundo)

**Abstract:**

Closely related to the gannets (Morus), the Genus Sula (Brisson, 1760) occurs widely in island and coastal regions of the world and, in respect to breeding biology, several localities shows different breeding patterns and seasonal variations. Three species occurs in Brazil among the seabirds species of the Fernando de Noronha Archipelago, the Masked Booby (Sula dactylatra), the Red-footed Booby (Sula sula) and the Brown Booby (Sula leucogaster). Fernando de Noronha consists of 21 oceanic islands present in the South Atlantic region (3º51'13″N, 32º25'25″O) and its climate present a dry (August to February) and a rainy season (March to July; Aw Köppen-Geiger CC). In this context, we analyzed Sula spp. population counts to assess similarities and differences in their breeding patterns in each climatic season. Semiannually, from 2018 to 2019, we surveyed active nests through remote visual census (Lugan® 10x42m binoculars) and direct counting of nearby nests to identify the number of eggs and nestlings stages. For all species, reproductive activities were verified in both seasons, there was no statistical difference in seasonality considering the number of breeding pairs, although a very high peak of active nests was noted in May 2018. However, there was a difference between the average proportion of the number of nestlings per active nest in S. sula (rainy: 5.4%, dry: 62.7%) and S. dactylatra (rainy: 32.9%; dry: 95.8%). These data indicate that the reproductive period and breeding behavior, as nest formation and mating, happens largely along the year and differs subtly among Sula species. The present study corroborates with other researches, showing that the Boobies' breeding appears to occur throughout the seasons with fluctuations connected to climatic conditions and feeding factors. A long term monitoring program for these species is underway and potentially monthly surveys that have initiated may support further information about theirs phenological characteristics.

**Authors:**

Lucas Santos¹, Ricardo Krul², Hellen Rocha¹, Patricia Serafini¹

¹Chico Mendes Institute of Biodiversity Conservation, ²Brazilian Institute for Conservation Medicine (Tríade)

Breeding seasons of sula spp. in fernando de noronha archipelago

**Abstract:**

Homeothermic marine divers in Polar regions face an energetic bottleneck in winter. With their relatively small body size and limited fat stores, the challenges of short days and cold temperatures at high latitudes are exacerbated for seabirds. We used light-temperature-depth recorders to examine the role of marine habitat, day length, moon illumination, and the state of the North Atlantic Oscillation (NAO) on strategies thick-billed murres use to survive winter in the Northwest Atlantic. We found that murres made regular use of two distinct marine provinces: cold (-0.1 ± 1.2 °C), shallower water along the Labrador and Greenland Shelves and warmer (3.1 ± 0.3 °C), deep water in the Labrador Basin. In the cold shelf water, murres used a feasting strategy, with more flying and less foraging each day, resulting in high daily energy expenditure but also high apparent energy intake; this strategy was most evident in early winter when day lengths were shorter. Murres in warmer basin water employed a night-feeding strategy, with more foraging under low light conditions (nautical twilight and night). In warmer basin water, murres increased diving at night when the moon was full, likely taking advantage of diel vertically migrating prey. Changes in daily NAO had direct effects on the behaviour of murres in warmer basin water: under negative NAO, murres dove more at night and foraging efficiency increased, while under positive NAO, murres dove mostly during the day and foraging efficiency declined. Individual murres were able to use both habitats and both strategies, feasting and night-feeding, with significant flexibility in the amount of time individual murres used these two habitats. Warmer waters within the Labrador Basin provide an important and under-appreciated habitat for thick-billed murres, and potentially other seabird species, in mid-winter. The proximity of two distinct marine habitats in this region could be advantageous to wintering seabirds, providing a selection of foraging options to cope with the challenges of winter.

**Authors:**

Allison Patterson¹, Grant Gilchrist², Dave Fifield², April Hedd², Greg Robertson², Kyle Elliott¹

¹McGill University, ²Environment and Climate Change Canada

Behavioural flexibility in the face of energetic constraints: diverse winter foraging strategies of an Arctic seabird

**Abstract:**

An introduction to a population ecology study of Black Guillemots Cepphus grylle in Iceland. The species has been studied on Flatey island over 40 years. Comparative information of certain aspects is available from neighbouring islands.

**Authors:**

Aevar Petersen¹

¹Independent researcher

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Time-lapse cameras on guano islands of Peru: Reliable and accurate tools to determine breeding sucess, trip length and breeding phenology of Peruvian boobies

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