United States

**Abstract:**

Density dependent prey depletion around breeding colonies has long been proposed as an important factor controlling the population dynamics of colonial animals. Colonial breeding provides benefits to members via information sharing and reduced predation, but may create costs via negative density-dependence. Using tracking data from murres (Uria spp.), the world&#39;s most densely breeding seabirds, we show that the frequency distribution of foraging trip distances scales to the 0.31 power of colony size during the chick-rearing stage, consistent with Ashmole&#39;s Halo theory. This pattern was evident across colonies varying in size over three orders of magnitude and distributed throughout the North Atlantic region. The strong relationship between colony size and foraging range means that important foraging habitat for some colonial species can be efficiently delineated based solely on population estimates. Protected areas covering the foraging ranges of the 17 largest colonies would safeguard two-thirds of the North Atlantic population; currently, only two of those colonies have significant coverage by marine protected areas. Our results represent an important example of how behavioural modelling, in this case Ashmole&#39;s version of central place foraging theory, can be applied to inform conservation and management in colonial breeding species.

**Authors:**

Allison Patterson¹, Grant Gilchrist², Anthony Gaston², Sigurd Benjaminsen³, Mark Bolton⁴, Sebastien Descamps³, Kjell Erikstad⁵, Morten Frederiksen⁶, Jannie Linnebjerg⁶, Oliver Love⁷, Mark Mallory⁸, Flemming Merkel⁶, William Montevecchi¹, Anders Mosbech⁶, Ellie Owen⁴, Paul Regular⁹, Tone Reiertsen⁵, Yan Ropert-Coudert¹⁰, Thorkell Thórarinsson¹¹, Anne Sophie Bonnet-Lebrun¹², Gail Davoren¹³, Julia Gulka¹³, Jonas Hentati-Sundberg¹⁴, Nicholas Huffeldt⁶, Kasper Johansen⁶, Aili Labansen¹⁵, Olof Olsson¹⁶, Norman Ratcliffe¹², Hallvard Strøm¹⁷, Kyle Elliott¹

¹McGill University, ²Environment and Climate Change Canada, ³Norwegian Polar Institute, ⁴Royal Society for the Protection of Birds, ⁵Norwegian Institute for Nature Research, ⁶Aarhus University, ⁷Windsor University, ⁸Acadia University, ⁹Fisheries and Oceans Canada, ¹⁰Centre d&#39;Etudes Biologiques de Chizé, ¹¹Northeast Iceland Nature Research Centre, ¹²British Antarctic Survey, ¹³University of Manitoba, ¹⁴Swedish University of Agricultural Sciences, ¹⁵Greenland Institute of Natural Resources, ¹⁶Stockholm University, ¹⁷Norwegian Polar Institute, FRAM Centre

3rd World Seabird Conference

Foraging range scales with seabird colony size

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:**

Density dependent prey depletion around breeding colonies has long been proposed as an important factor controlling the population dynamics of colonial animals. Colonial breeding provides benefits to members via information sharing and reduced predation, but may create costs via negative density-dependence. Using tracking data from murres (Uria spp.), the world's most densely breeding seabirds, we show that the frequency distribution of foraging trip distances scales to the 0.31 power of colony size during the chick-rearing stage, consistent with Ashmole's Halo theory. This pattern was evident across colonies varying in size over three orders of magnitude and distributed throughout the North Atlantic region. The strong relationship between colony size and foraging range means that important foraging habitat for some colonial species can be efficiently delineated based solely on population estimates. Protected areas covering the foraging ranges of the 17 largest colonies would safeguard two-thirds of the North Atlantic population; currently, only two of those colonies have significant coverage by marine protected areas. Our results represent an important example of how behavioural modelling, in this case Ashmole's version of central place foraging theory, can be applied to inform conservation and management in colonial breeding species.

**Authors:**

Allison Patterson¹, Grant Gilchrist², Anthony Gaston², Sigurd Benjaminsen³, Mark Bolton⁴, Sebastien Descamps³, Kjell Erikstad⁵, Morten Frederiksen⁶, Jannie Linnebjerg⁶, Oliver Love⁷, Mark Mallory⁸, Flemming Merkel⁶, William Montevecchi¹, Anders Mosbech⁶, Ellie Owen⁴, Paul Regular⁹, Tone Reiertsen⁵, Yan Ropert-Coudert¹⁰, Thorkell Thórarinsson¹¹, Anne Sophie Bonnet-Lebrun¹², Gail Davoren¹³, Julia Gulka¹³, Jonas Hentati-Sundberg¹⁴, Nicholas Huffeldt⁶, Kasper Johansen⁶, Aili Labansen¹⁵, Olof Olsson¹⁶, Norman Ratcliffe¹², Hallvard Strøm¹⁷, Kyle Elliott¹

¹McGill University, ²Environment and Climate Change Canada, ³Norwegian Polar Institute, ⁴Royal Society for the Protection of Birds, ⁵Norwegian Institute for Nature Research, ⁶Aarhus University, ⁷Windsor University, ⁸Acadia University, ⁹Fisheries and Oceans Canada, ¹⁰Centre d'Etudes Biologiques de Chizé, ¹¹Northeast Iceland Nature Research Centre, ¹²British Antarctic Survey, ¹³University of Manitoba, ¹⁴Swedish University of Agricultural Sciences, ¹⁵Greenland Institute of Natural Resources, ¹⁶Stockholm University, ¹⁷Norwegian Polar Institute, FRAM Centre

symposium

**Abstract:**

Intraspecific competition for food can be especially high in colonial breeding seabirds. To minimize colony-induced or annual foraging challenges, the diet may vary among individuals, but few studies have simultaneously investigated the effects of both extrinsic conditions (e.g. colony, year effects) and parameters of an individual (e.g. sex, age, individual quality) on diet in seabirds. Using stable isotope analyses, we studied the diet of 214 Adélie penguins of known sex, age and breeding quality, nesting in two colonies on Ross Island, Antarctica, over three breeding seasons. During the study, δ15N and δ13C isotope values were lower in penguins breeding at Cape Crozier compared to those at Cape Bird, resulting in a difference in estimated prey proportions. Cape Bird penguins consistently consumed more energy-rich silverfish, while birds at Cape Crozier ate more crystal krill. We also found inter-annual differences in diet, with a higher dietary fish proportion in both colonies during 2011. Males had significantly higher δ15N values, indicating that males consumed more fish than females. This sexual segregation in diet was particularly pronounced at Cape Bird, where the overall isotopic niche was wider than at Cape Crozier. Differences in diet among adults of varying ages only existed at Cape Bird, where middle-aged penguins consumed more fish than old and young penguins. This study provides evidence that penguin diet is largely driven by annual, seasonal and local abundances of prey, with only some individuals selectively foraging for more nutritional prey if prey choices are present.

**Authors:**

Melanie Massaro¹, David Ainley², Jarrod Santora³, Petra Quillfeldt⁴, Amélie Lescroël⁵, Amy Whitehead⁶, Arvind Varsani⁷, Grant Ballard⁵, Phil Lyver⁸

¹Charles Sturt University, ²H.T. Harvey & Associates, ³University of California, ⁴Justus Liebig University Giessen, ⁵Point Blue Conservation Science, ⁶National Institute of Water and Atmospheric Research, ⁷Arizona State University, ⁸Manaaki Whenua Landcare Research

Diet segregation in Adélie penguins: some individuals attempt to overcome colony-induced and annual foraging challenges

**Abstract:**

Short-tailed shearwater (STSH) breeding in Tasmania employs a dual foraging strategy and they feed in the Southern Ocean during long trips. In the Southern Ocean, Antarctic krill (krill) is a key species, while myctophids can be one of alternatives. In the Indian sector, where krill abundance is relatively low compared to the Scotia-Weddell Sea, krill-independent food web may be developed regionally. In this sector krill-dependent food web may be dominant over the continental slope while krill-independent food web may be in oceanic zone. To understand how does STSH move in these two habitats in the Indian sector, we tracked individuals using GPS logger and identified prey species of tracked individuals using fatty acid signature of stomach oils. We collected 14 long trip tracks and two oil samples from STSH breeding on Wedge Island in Tasmania in Jan- Feb 2019. Two core-use areas (50% kernel density) were recognized. One (named "core-2") was in 160°E 67°S l in the continental slope zone and the other ("core-3") was in 120°E 57°S in the oceanic zone. 93% of birds used Core-2 during the long trips. We analyzed fatty acid composition of stomach oil in two birds spending 7 days in 2core area before visiting the colony. The fatty-acids profile indicated that the two birds fed on myctophids. Core-3 might also be important to some extent but no diet samples were available at this moment. This study indicates that at least some individuals fed on myctophids even over the continental slope. This study indicate the importance of myctophids in the Southern Ocean ecosystem.

**Authors:**

Sarara Azumi¹, Yutaka Watanuki¹, Akinori Takahashi², Nobuo Kokubun², Yasuhiro Ando¹, Masato Moteki³, Fernando Arce Gonzalez⁴, Mary-Anne Lea⁴, Mark Hindell⁴

¹Hokkaido University, ²National Institute of Polar Research, ³Tokyo University of Marine Science and Technology, ⁴University of Tasmania

Foraging movement of short-tailed shearwater in the Southern Ocean

**Abstract:**

Breeding Adélie penguins forage at sea and return to land to provision their chicks, adjusting their foraging behaviour in response to environmental fluctuations over time. At Béchervaise Island, a nesting site in an East Antarctic population, Adélie penguin diving behaviour remains undocumented. This represents a key area of uncertainty in efforts to understand and predict foraging success at this colony. We compiled a multi-year telemetry dataset from time−depth recorders deployed from 1992 to 2004 on 64 birds at Béchervaise Island. We examined diving activity at multiple scales, ranging from foraging trips (n = 125) to dive bouts (n = 3461) to individual dives (n = 84 521), and then characterised the stage- and sex-specific variation in diving behaviour of chick-rearing Adélie penguins using linear mixed effect models. Total foraging trip effort (trip duration, number of dives, vertical distance travelled and number of wiggles [a proxy for prey ingestion]) substantially increased as the chick-rearing period progressed (guard through crèche), consistent with increasing chick provisioning and self-maintenance requirements over time. Foraging activity was predominantly structured in periods of sustained diving bouts, indicating sustained foraging effort over the course of the foraging trip. Diving behaviour (dive-level depth, duration, bottom time and attempts of catch per unit effort) varied in relation to sex and chick-rearing stage. Dives were performed more frequently during high and low levels of solar light, which is likely linked to visual predation strategies or prey activity. Our findings advance our understanding of this population's foraging behaviour, which is ultimately required to underpin the conservation and management of this breeding colony.

**Authors:**

Javed Riaz¹, Sophie Bestley¹, Simon Wotherspoon¹, Julien Freyer¹, Louise Emmerson²

¹Institute for Marine and Antarctic Studies, University of Tasmania, ²Australian Antarctic Divison

From dives to bouts to trips: temporal patterns in the diving behaviour of chick-rearing Adélie penguins, East Antarctica

**Abstract:**

The enigmatic Fiordland penguin, or tawaki, remain one of the least known penguin species. Recent surveys suggest that tawaki populations are increasing which is in stark contrast to other eudyptid penguins that have undergone steep declines. Despite their limited distribution along a mere 500 kilometer stretch of coastline in New Zealand's rugged and inaccessible southwest, tawaki occupy remarkably diverse marine habitats. In 2014, the Tawaki Project set out to study the penguins' ecology across their breeding range. We examined their foraging behavior during and outside of the breeding season at three sites representative of the species' varied marine habitats. Over the course of six years, we documented the impact of El Niño on foraging range and breeding success and tracked extreme long-distance movements in the pre-moult and wintering periods. These data paint an intriguing picture of a crested penguin species that lives outside the zone occupied by congeners (subtropical instead of sub-Antarctic waters). They show remarkable versatility in their foraging strategies depending on available marine habitat. During the pre-moult, tawaki travel much farther distances than any other penguin species, and during their even longer winter migration they forage as far as the Polar Front. Apparently, tawaki can afford the costs of these marathon journeys, which not only exposes the species' sub-Antarctic origins but also indicates considerable adaptability. In the face of significant environmental change, doing things differently than other crested penguins appears to be tawaki's secret of success.

**Authors:**

Ursula Ellenberg¹, Thomas Mattern¹, David Houston², Robin Long³, Klemens Pütz⁴, Pablo Garcia Borboroglu⁵, Philip Seddon⁶

¹Global Penguin Society/ Eudyptes EcoConsulting, ²Department of Conservation, ³West Coast Penguin Trust, ⁴Antarctic Research Trust, ⁵Global Penguin Society/ Centro Nacional Patagónico (CONICET), ⁶University of Otago

Sprint-ace and marathon penguin: How Fiordland penguins/ tawaki defy clichés about crested penguin marine ecology - and appear to do great

**Abstract:**

Gulls are one of the very few avian taxa to occur on all continents, and many species have adapted remarkably well to living alongside humans in urban environments. Paradoxically, many of these species continue to experience overall population declines, even as urban-nesting populations grow. In this talk, we will present details about several gull species that occupy the Pacific coast of North America: Glaucous-winged (Larus glaucescens), Western (L. occidentalis), Herring (L. argentatus), Mew (L. canus), and Heermann's (L. heermanni). Drawing on six years of field work across Canada and the US, we will compare and contrast the urban ecologies of these species with those of their declining, non-urban conspecifics. Nest site demographics, as well as colony density, nest fidelity, and reproductive success figures will be presented. We will also discuss several spatial models that we have developed to predict urban-nesting behaviour in these species. As urban-nesting becomes more commonplace, a host of new human-wildlife conflicts can arise, as well as many exciting conservation opportunities. These issues and ideas demand a deeper knowledge of the breeding ecology of urban gulls, and our work represents another step toward this.

**Authors:**

Edward Kroc¹, Louise Blight²

¹University of British Columbia, ²Procellaria Research & Consulting

Urban gulls of the Pacific coast of North America: Balancing wildlife conflict concerns with the protection of urban breeding sites

**Abstract:**

The two species of yellow-nosed albatross, Atlantic (Thalassarche chlororhynchos) and Indian (Thalassarche carteri), are morphologically similar, however, they show some differences in behaviour and breeding range. We studied genetic variation within and among the two species using nuclear (microsatellite, Pema7 and Occa9) and mitochondrial (control region) markers. We analysed 201 samples of Atlantic yellow-nosed albatross from Nightingale, Inaccessible and Gough Islands and 33 samples of Indian yellow-nosed albatross from Amsterdam Island. Both sets of markers differentiated the two species. Microsatellite and Occa9 nuclear markers revealed two genetically distinct groups within Atlantic yellow-nosed albatross, grouping birds from Nightingale and Inaccessible Islands together and separating birds from Gough Island. Differences in at-sea distribution might have resulted in genetic differentiation within Atlantic yellow-nosed albatross, but there is no evidence currently of such differences. Both species are listed as endangered due to their limited number of breeding sites and threats from introduced diseases, introduced predators and fishing mortality. Our results contribute to conservation and management plans for the two species, and suggest the need for separate management of the two genetically distinct groups of Atlantic yellow-nosed albatross breeding at the Tristan group (80%) and Gough Island (20%). Key words: yellow-nosed albatross, genetic variation, microsatellite, nuclear marker

**Authors:**

Dilini Abeyrama¹, Zach Dempsey¹, Peter Ryan², Theresa Burg¹

¹University of Lethbridge, ²FitzPatrick Institute of African Ornithology

Speciation and population differentiation in yellow-nosed albatrosses

**Abstract:**

Species migratory behaviour and preferences in oceanic habitats respond to dynamic changes in their environment, they will adapt their foraging strategies which can impact predator-prey relationships, displace other species, change species range or alter their annual cycle. Wedge-tailed shearwaters Ardenna pacifica are a migratory procellariiform found throughout the Pacific and Indian Oceans, utilising a variety of tropical and sub-tropical habitats and breeding across a wide latitudinal range that recently has been extending poleward. Information on their diet, niche breadth and habitat utilisation has not been well-documented for populations at their southern-most extent, with limited information of this species from temperate south-eastern Australia. Wedge-tailed shearwaters were tracked over a three-year period across two distinct latitudinal breeding colonies (temperate versus sub-tropical) from south-eastern Australia, with both populations showing high-levels of winter site-fidelity and dietary consistency. This was not the case during the breeding phase, with clear habitat partitioning exhibited with the temperate population targeting an area much further south on or near the sub-tropical frontal zone (STFZ). The results identified a staging trip just prior to their northern migration down to the STFZ for all three years for the temperate population and less predictably for the sub-tropical population. The analysis from feather stable isotopes revealed different foraging strategies exhibited during the breeding phase with a degree of trophic δ15N and habitat δ13C variation. The results from this study, show clear habitat partitioning occurred between populations and a high degree of plasticity between years.

**Authors:**

Penny Beaver¹, Mary-Anne Lea¹, Nicholas Carlile²

¹University of Tasmania, ²NSW Department of Premier and Cabinet

A comparative study of a temperate and subtropical, small procellariiform, the Wedge-tailed shearwater Ardenna pacifica in southeastern Australia

**Abstract:**

The Gulf of Mane (Northwest Atlantic) supports a long-term and large-scale seabird monitoring program, encompassing more than a dozen colonies and thirty years of data. This ecosystem has been subject to marine heatwaves and steep declines in commercially fished Atlantic herring (Clupea harengus), allowing for a variety of investigations into seabird-ecosystem relationships. We present two studies involving large-scale data collection that each revealed new insights into ecosystem quality and function. One study linking seabird chick provisioning data to fishery and fishery-independent herring data indicated that herring declines were not uniform across the ecosystem; the relevant management units used by the fishery obscured smaller-scale changes to herring abundance that were particularly severe in the east. Seabird data also potentially illustrate movements of juvenile herring and show that Canadian-origin herring spend their first summers in the USA. Our second study examines the population dynamics and habitat quality of Arctic Terns (Sterna paradisaea), typically a widely dispersed and inaccessible seabird. We determined the source-sink status of each colony annually in our metapopulation, and linked it to habitat quality over 27 years. Each colony had unique diet profiles that prevented any single variable from being used as an index, but when examined together indicated high-quality and low-quality years. Impacts of mesopredator Laughing Gulls (Leucophaeus atricilla) were nearly impossible to quantify at a local scale, but became clearer at a metapopulation scale, inhibiting reproductive success and demographic contribution. These insights would not have been possible without data from multiple colonies, which allowed for synergistic conclusions.

**Authors:**

Lauren Scopel¹, Antony Diamond¹, Stephen Kress², Paula Shannon³, Linda Welch⁴, Sara Williams⁴

¹University of New Brunswick, ²Cornell University, ³National Audubon Society Seabird Restoration Program, ⁴U.S. Fish and Wildlife Service

Dynamics of prey and predator movements in linked metapopulations

**Abstract:**

Plasticity in foraging behavior among individuals within a colony can reduce competition but few studies have compared the generality of foraging patterns among individuals from multiple breeding colonies. Western gulls (Larus occidentalis) are generalist foragers that consume a range of marine and terrestrial foods but multi-colony comparisons are limited. Here, we used tail-mounted GPS loggers to compare the foraging behavior of 156 western gulls breeding at seven colonies ranging from southern California to Oregon, USA. Colonies varied dramatically in population size (100 to 10,000 nests) and distance from the mainland (<1 to 60 km). Foraging behavior was significantly influenced by proximity to urban centers (e.g. Los Angeles & San Francisco) where gulls traveled farther (>150 km roundtrip) and for longer durations (12-24 hrs) compared to foraging excursions at sea. More than 50% of all gulls (predominantly from the largest colonies) exhibited a mixture of marine and terrestrial foraging whereas gulls from both smaller colonies in Oregon foraged mainly at sea. Foraging sites on land included landfills, waste management centers, and parks whereas marine habitats were primarily over neritic waters or along coastlines. Colony-specific home range varied with colony size (2,034 km^2 vs. 14,230 km^2, smallest and largest colony, respectively) as did mean individual home ranges (309 ± 311 SD km^2 vs. 986 ± 786 SD km^2, respectively), consistent with greater resource competition. Population-level plasticity in foraging behavior was evident and dependent on habitat type. In general, gulls from the larger more distant colonies were away longer when foraging in terrestrial habitats than gulls foraging at sea, and this may impact territorial defense and attempts at nest predation by conspecifics.

**Authors:**

Scott Shaffer¹, Rachael Orben², Pete Warzybok³, Russell Bradley⁴, Jaime Jahncke³, Leigh Torres², Robert Suryan⁵, Corey Clatterbuck⁶, Hillary Young⁷

¹San Jose State University, ²Oregon State University, ³Point Blue Conservation Science, ⁴California State University - Channel Islands, ⁵National Oceanic and Atmospheric Administration, ⁶San Diego State University, ⁷University of California

Devil's in the details: A multi-colony perspective on the foraging ecology of western gulls

**Abstract:**

Multi-colony studies of breeding seabirds may provide insights into the mechanistic links between large-scale climate variability and local changes in prey availability. In the North Pacific, the Pacific Decadal Oscillation (PDO) is a dominant climate index, characterized by contrasting effects on sea surface temperature between the western and eastern North Pacific. To examine how inter-annual variability in PDO affects rhinoceros auklets Cerorhinca monocerata across the North Pacific, we measured inter-annual changes in nutritional stress (as reflected in plasma levels of corticosterone) of adults breeding on five colonies (two and three colonies from the western and eastern Pacific, respectively). We also examined concurrent changes in mass and energy content of food loads delivered to chicks. We found that higher summer PDO values were associated with increased corticosterone levels and lower mass and energy contents of the food loads in both the western and eastern North Pacific colonies. Results indicate that higher summer PDO is associated with local changes in forage fish communities leading to reduced availability of energy-rich prey, which, in turn, increases the nutritional stress of breeding birds. We conclude that higher summer PDO index is associated with food-poor conditions for breeding rhinoceros auklets across their reproductive range, and prolonged periods of high summer PDO may be detrimental to the populations of this seabird species.

**Authors:**

Ui Shimabukuro¹, Akinori Takahashi², Jumpei Okado³, Nobuo Kokubun², Jean-Baptiste Thiebot⁴, Alexis Will⁵, Yutaka Watanuki³, BriAnne Addison⁶, Scott Hatch⁷, J. Mark Hipfner⁸, Leslie Slater⁹, Brie Drummond⁹, Alexander Kitaysky⁵

¹The Graduate University for Advanced Studies, SOKENDAI, ²The Graduate University for Advanced Studies, SOKENDAI & National Institute of Polar Research, ³Hokkaido University, ⁴National Institute of Polar Research, ⁵University of Alaska Fairbanks, ⁶Deakin University, ⁷Institute for Seabird Research and Conservation, ⁸Pacific Wildlife Research Centre, ⁹U.S. Fish and Wildlife Service

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Next from 3rd World Seabird Conference

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Understanding the spatio-temporal seabird population responses to climate change.

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