United States

**Abstract:**

In marine systems, resources are patchy and scattered over large spatial scales so that top predators like seabirds often rely on specific higher quality foraging zones (e.g. shelf edges, upwellings) that are predictable over years. Site fidelity is driven by predictable resource distributions in time and space. However, intrinsic factors related to the individual&#39;s physiology and life-history traits can contribute to consistent foraging behaviour and movement patterns. Using 11 years of continuous geolocation tracking data (fall 2008 to spring 2019), we investigated spatiotemporal consistency in non-breeding movements in a pelagic seabird population of black-legged kittiwake (Rissa tridactyla) breeding in the High Arctic (Svalbard). Our objective was to assess the relative importance of spatial versus temporal repeatability behind inter-annual movement consistency during winter. Most kittiwakes used pelagic regions of the western North Atlantic. Winter site fidelity was high both within and across individuals and at meso (100-1000 km) and macro scales (&gt;1000 km), including over deep-water areas far from continental shelves. Spatial consistency in non-breeding movement was higher within than among individuals, suggesting that site fidelity might emerge from individuals&#39; memory to return to locations with predictable resource availability. Consistency was also stronger in space than in time, suggesting that it was driven by consistent resource pulses that may vary in time more so than in space. Specialization for key wintering areas can indicate vulnerability to environmental perturbations, with winter survival and carry-over effects arising from winter conditions as potential drivers of population dynamics.

**Authors:**

Don-Jean Léandri-Breton¹, Kyle Elliott¹, Pierre Legagneux², Børge Moe³, Olivier Chastel⁴, Arnaud Tarroux⁵, Frédéric Angelier⁴, William Jouanneau⁴, Pierre Blévin⁶, Per Fauchald⁵, Sabrina Tartu⁴, Aurélie Goutte⁷, Vegard Sandøy Bråthen⁵

¹McGill University, ²Université Laval, ³Norwegian Institute for Nature Research (NINA), ⁴Centre d&#39;Études Biologiques de Chizé (CEBC-CNRS) &amp; Université de La Rochelle, ⁵Norwegian Institute for Nature Research, ⁶Akvaplan-NIVA, ⁷École Pratique des Hautes Études

3rd World Seabird Conference

Long-term tracking of an Arctic-breeding seabird indicates high fidelity for pelagic wintering areas

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:**

In marine systems, resources are patchy and scattered over large spatial scales so that top predators like seabirds often rely on specific higher quality foraging zones (e.g. shelf edges, upwellings) that are predictable over years. Site fidelity is driven by predictable resource distributions in time and space. However, intrinsic factors related to the individual's physiology and life-history traits can contribute to consistent foraging behaviour and movement patterns. Using 11 years of continuous geolocation tracking data (fall 2008 to spring 2019), we investigated spatiotemporal consistency in non-breeding movements in a pelagic seabird population of black-legged kittiwake (Rissa tridactyla) breeding in the High Arctic (Svalbard). Our objective was to assess the relative importance of spatial versus temporal repeatability behind inter-annual movement consistency during winter. Most kittiwakes used pelagic regions of the western North Atlantic. Winter site fidelity was high both within and across individuals and at meso (100-1000 km) and macro scales (>1000 km), including over deep-water areas far from continental shelves. Spatial consistency in non-breeding movement was higher within than among individuals, suggesting that site fidelity might emerge from individuals' memory to return to locations with predictable resource availability. Consistency was also stronger in space than in time, suggesting that it was driven by consistent resource pulses that may vary in time more so than in space. Specialization for key wintering areas can indicate vulnerability to environmental perturbations, with winter survival and carry-over effects arising from winter conditions as potential drivers of population dynamics.

**Authors:**

Don-Jean Léandri-Breton¹, Kyle Elliott¹, Pierre Legagneux², Børge Moe³, Olivier Chastel⁴, Arnaud Tarroux⁵, Frédéric Angelier⁴, William Jouanneau⁴, Pierre Blévin⁶, Per Fauchald⁵, Sabrina Tartu⁴, Aurélie Goutte⁷, Vegard Sandøy Bråthen⁵

¹McGill University, ²Université Laval, ³Norwegian Institute for Nature Research (NINA), ⁴Centre d'Études Biologiques de Chizé (CEBC-CNRS) & Université de La Rochelle, ⁵Norwegian Institute for Nature Research, ⁶Akvaplan-NIVA, ⁷École Pratique des Hautes Études

technical paper

**Abstract:**

Many animal species show sexually divergent foraging behaviours reflecting different physiological constraints or energetic needs. However, the mechanism behind these observed differences is often poorly understood. Here we investigate fine-scale sex-based differences in foraging behaviour of a sexually monomorphic seabird, the northern gannet using a bioenergetics approach. We tracked 12 gannets using a combination of GPS and accelerometer loggers during the breeding season. Measures of dynamic body acceleration were converted to kilojoules to quantify foraging costs in relation to energy intake from diet. Male gannets were lighter than female gannets, and dive rate was lower in males than females. However, sex differences in dive energetics were relatively minor, male plunge dives were energetically cheaper, while male pursuit dives were energetically more expensive than for females. Stable isotope analysis of blood samples was used to model individuals' diet through Bayesian mixing models, which informed average kilojoule intake values from successful prey capture attempts. We then calculated minimum prey capture success rates to sustain movement, maintain body condition, and provision chicks during a foraging trip. While there were no obvious differences in calorific intake between the sexes, males had higher minimum prey capture success rates and due to the lower number of dives performed, must be 14% more successful than females when engaging in prey capture attempts. Our study suggests that sex-specific differences in foraging can be mediated by differences in prey capture, and that these differences may be more nuanced and widespread than previously thought.

**Authors:**

Ashley Bennison¹, Joan Giménez¹, John Quinn¹, Mark Jessopp¹

¹University College Cork

Sex, prey capture rates, and the bioenergetics of foraging in the northern gannet

**Abstract:**

The massive concentration of seabirds in small terrestrial habitats for breeding can encompass a pulsed, predictable, and high-quality feeding resource for terrestrial predators. The Striated caracara (Phalcoboenus australis) is a globally Near Threatened raptor specialized in the exploitation of seabird colonies during breeding season. In a 4 Km2 bay in Isla de los Estados, Argentina, near 300,000 seabirds breed between September and late March. In order to understand the level of dietary dependence on local marine resources, we examined breeding behavior and intra-specific variation in the trophic niche of caracaras during breeding season using stable isotope and pellet analysis. All nests of caracaras were associated mainly with the rockhopper penguin (Eudyptes chrysocome) colony on the island. Isotopic niche varied with, age, breeding status, and, year, but in all cases over 75% of their diet came from seabird colonies. Pellet analysis showed a similar pattern, with down feathers, feathers and eggs of penguins present in over 80% of the samples. Mercury (Hg) analysis in feathers suggest high levels of contamination, with adult feathers averaging over 26 mg/kg. Rockhopper penguins have been reported to present high levels of Hg in the area, thus this high dependence of caracaras on penguin prey represents a higher vulnerability for this caracara population. Overall, seabirds, and especially rockhopper penguins, appears to modulate trophic ecology and mercury exposure of its main terrestrial predator.

**Authors:**

Ulises Balza¹, Nicolás Lois², Klemens Pütz³, Michael Polito⁴, Rebecka Brasso⁵, Andrea Raya-Rey¹

¹Centro Austral de Investigaciones Científicas (CADIC-CONICET), ²Instituto de Ecología, Genética y Evolución de Buenos Aires (IEGEBA-CONICET), ³Antarctic Research Trust, ⁴Louisiana State University, ⁵Weber State University

Seabird's pulsed abundance modulates breeding season ecology and mercury exposure of a highly associated bird of prey

**Abstract:**

Wedge-tailed Shearwaters (WTS) are one of the most abundant seabird species breeding in the western Indian Ocean, thus intra-specific competition is expected to be high, especially between neighbouring colonies. Here we examined the foraging ecology of incubating WTS from Réunion Island as well as D'Arros and Fouquet Island, two neighbouring Islands in Seychelles. We aimed to (1) map the foraging distribution of WTS and relate them to abiotic factors, (2) compare the flight characteristics of the three colonies and lastly, (3) assess the potential spatial segregation and/or overlap between neighbouring colonies. Birds were equipped with GPS loggers and foraging distributions were calculated using Fixed kernel utilization distributions. Variability in foraging behaviour (i.e. foraging plasticity) at sea was illustrated in the different flight characteristics of WTS from different colonies. Foraging plasticity was mainly observed in the WTS flight bearing, flight duration and the maximum distance travelled from the colony. Shearwaters displayed dissimilar levels of site fidelity at each site and were faithfully observed foraging in one direction from Réunion but were observed foraging in various directions from Seychelles. Foraging effort between shearwaters from Fouquet and Réunion was also significantly lower with shearwaters from Fouquet spending less time at sea and foraged closer to their colony. There were no significant differences in flight characteristics between neighbouring colonies in Seychelles and it is possible that the colonies are acting as sub-colonies of an individual breeding site since they are only separated by a narrow channel. These behavioural differences between colonies suggests a high level of behavioural plasticity which is likely to benefit the species when needing to adjust to expected future environmental changes.

**Authors:**

Danielle Keys¹, Pierre Pistorius¹, Matthieu Le Corre², Ryan Daly³

¹DST/NRF Centre of Excellence at the Percy FitzPatrick Institute, Nelson Mandela University, Departme, ²Laboratory of Marine Ecology (ECOMAR), University of La Réunion, ³Save Our Seas Foundation

Friendly neighbours and plastic behaviours: comparative foraging ecology of Wedge-tailed Shearwaters (Ardenna pacifica) breeding in the tropical western Indian Ocean

**Abstract:**

The Yelkouan Shearwater (Puffinus yelkouan) is a Mediterranean endemism, classified as Vulnerable following its decreasing population trend. Between 27-60% of the 21-36,000 pairs estimated at the global level breed at a single site of ca. 6 sqkm, the island of Tavolara (Italy 40°54'N 09°42'E). GPS tracking of 22 adults (60 tracks) during the 2011-2015 breeding seasons describe a trans-national foraging range which stretches across the NW Mediterranean Sea, between the western coast of Sardinia island, Italy (39°50'N 08°13'E) and the Gulf of Lion, France (43°00'N 03°40'E). Within this wide area, core foraging clusters obtained from tracks during incubation (N=44) and chick-rearing (N=16) overlap areas of primary productivity blooms, which in the Mediterranean typically lie in coastal areas close to river estuaries. In particular, the Gulf of Lion (Rhone river mouth) represents the final destination of all trips during chick-rearing. The Mediterranean sea is featured by a generally low primary production and estuaries represent seasonally-predictable productivity hotspots during boreal spring and summer. Foraging trips entail long-distance flights lasting up to 10 days, and their duration increases during the breeding season (median value during incubation 2.0 days, vs 6.5 days during chick growth), when food requirements are at their maximum and areas rich of food are far from the colony and very localised.

**Authors:**

Marco Zenatello¹, Francesco Pezzo¹, Giulia Cerritelli², Augusto Navone³, Dimitri Giunchi², Giovanna Spano³, Enrica Pollonara², Alessandro Massolo², Anna Gagliardo², Nicola Baccetti¹

¹ISPRA (Italian Institute for Environmental Protection and Research), ²University of Pisa, ³Marine Protected Area Tavolara - Punta Coda Cavallo

The largest colony in the smallest kingdom of the world: the tale of Yelkouan shearwaters from Tavolara island (Italy)

**Abstract:**

Knowledge of the dispersion of seabirds during migration may provide information on predictable foraging areas, potential overlap with human activities and target conservation zones. The aim of this study was to analyze spatial distribution of Southern rockhoppers penguins -RP- (Eudyptes chrysocome chrysocome) and Magellanic penguins -MP- (Spheniscus magellanicus) during migration. We used geolocators (MK3 & MK4) to study migration movements of 10 RP breeding at Isla Pingüino (47°54'S; 65°43'W) and 20 MP breeding at Isla Quiroga (47°45'S, 65°53°W), Argentina, during 2019. We found that both male and female RP moved north, reaching the northern Uruguayan coast (32°30'), but southward, males traveled farther than females, reaching latitudes as far south as the Antarctic ocean. Males spend 33% of their time, while females only spend 7% of their time south of their breeding colony. Males dispersed more than females: latitudinal length (distance between northernmost and southernmost points) was 2250 km for females and 3250 km for males, and area according to the 50% Kernel density contour was threefold larger for males than for females. Males traveled farther offshore than females (190 km males vs. 145 km females) and spent more time in colder waters than females. Migration movements of MP have been described previously and were similar to RP female dispersion, but very different from RP males distribution. Latitudinal length for PM was 2100 km and they used warmer waters than RP. Area overlap (50% Kernel contour) between RP and MP was about 40-60% during April-May; 30% in June-July and no overlap in August. Female RP were exclusively responsible for these shared areas because male RP were farther south and farther offshore, even beyond the continental shelf. Different diets and breeding schedules might be responsible for the segregation between species. This study shows sexual segregation in RP at latitudinal and longitudinal levels, and an overlap between MP and female RP winter areas.

**Authors:**

melina barrionuevo¹, Annick Morgenthaler², Ana Millones², Nahuel Marchisio¹, Esteban Frere¹

¹UNPA-CONICET, ²UNPA

Winter ground segregation between two neighboring breeding penguins

**Abstract:**

The theory of competitive exclusion predicts that, when the resources are limited, species with similar trophic requirements can only coexist if there are differences in some dimensions of their ecological niche. The estuary of Ría Deseado, in Argentina, is one of the few places in the world where four species of cormorants coexist: the Red-legged cormorant (Poikilocarbo gaimardi), the Rock shag (Leucocarbo magellanicus), the Imperial shag (L. atriceps) and the Neotropic cormorant (Nannopterum brasiliensis). To determine possible interspecific differences in one or more of their niche dimensions related to the use of resources during the breeding season, we studied the dietary (pellets), isotopic (stable isotope), spatial (foraging areas) and temporal (breeding calendar) dimensions of the trophic niche of these four sympatric species, between 2009 and 2013. We found that the Red-legged cormorant was located at a low trophic level; he fed almost exclusively on pelagic prey and segregated its core feeding areas from other species. The Rock shag was located at a high trophic level and presented the most benthic and diverse diet, including several invertebrate taxa. The Neotropic cormorant was situated at a similar trophic level as the Rock shag, with which it overlapped its isotopic niche, as well as its core feeding areas. The Neotropic cormorant fed only on fishes. Finally, the Imperial cormorant segregated isotopically, spatially and temporarily from the other species. Its trophic level was situated in between the Red-legged and the Rock-Neotropic group. Regarding the breeding calendar, the Neotropic cormorant was the most asynchronous species, and the one that presented the latest chick-rearing peak. In general, the four species showed a partition of the use of their resources despite occupying a rather restricted geographical space. The observed differences possibly act by reducing competition during the reproductive period when birds are restricted to exploit resources within a limited area. The multidimensional approach to study the use of the trophic resources of these four species allowed us to find that the degree of interspecific segregation varied according to the dimension examined.

**Authors:**

Annick Morgenthaler¹, Ana Millones¹, Patricia Gandini², Esteban Frere²

¹Centro de Investigaciones de Puerto Deseado, Universidad Nacional de la Patagonia Austral, ²Centro de Investigaciones de Puerto Deseado, Universidad Nacional de la Patagonia Austral, and CONIC

Dividing the pie: the use of trophic resource by four sympatric species of cormorants in a saltwater estuary from Southern Patagonia

**Abstract:**

Kelp Gulls Larus dominicanus are one of the most abundant gulls in the Southern Hemisphere and can play an important role in their ecosystem. Understanding their foraging ecology is therefore important, especially in the context of anthropogenic changes of the environment. Over 35,000 Kelp Gulls breed in South Africa but little is known about their habitat use. It has been hypothesised that foraging mainly occurs in natural habitats while provisioning chicks to ensure high quality food, but knowledge on their foraging ecology during the incubation period remains poor. We tracked incubating Kelp Gulls from six colonies distributed along the coast of South Africa, varying in their distance to urban areas and landfills, and compared foraging trip patterns and habitat selection between colonies. Gulls from west coast colonies, generally located further from landfills than the other studied colonies, travelled farther from their breeding sites (11.7 ± 9.9-17.8 ± 21.7 km, n = 3 colonies) than birds from Cape Town and south and east coast colonies (1.7 ± 0.8-3.1 ± 3.7 km, n = 3) with birds travelling farthest when foraging at sea. Gulls from all colonies spent more time foraging in marine, coastal, and natural terrestrial environments than scavenging in strongly modified habitats while incubating. Our results suggest that Kelp Gulls in South Africa are able to exploit various resources from different foraging habitats, regardless of colony location and seem to rely less on anthropogenic habitats than expected.

**Authors:**

Katharina Reusch¹, Nicolás Suárez², Peter Ryan³, Lorien Pichegru¹

¹Nelson Mandela University, ²Centro para el Estudio de Sistemas Marinos, CCT CENPAT-CONICET, ³FitzPatrick Institute of African Ornithology, University of Cape Town

Foraging movements of breeding Kelp Gulls in South Africa

**Abstract:**

Although our understanding of the foraging ecology of adult seabirds has been greatly enhanced by the development of biochemical analyses as well as the miniaturization of tracking devices, there remains limited information on important foraging areas during the non-breeding season. Even less is known about the spatial and dietary overlap of seabird species during the non-breeding season, which could lead to interspecific competition during low productivity winter conditions. We aimed to quantify spatial niche overlap among Common Murres (Uria aalge), Razorbills (Alca torda), and Atlantic Puffins (Fratercula arctica) outside the breeding season. Using data from geolocators deployed on puffins, razorbills, and murres during July 2019 and 2020 in coastal Newfoundland and retrieved the following summers, we developed kernel density maps throughout the non-breeding period in both years. Seasonal utilization distributions of each alcid species indicate low spatial overlap during most months in the non-breeding period, with exceptions in early fall, and for some puffins that overlapped with razorbills along the North American coast. Our next steps will combine these spatial analyses with exploration of isotopic niche overlap, using bulk and compound-specific stable isotope analysis of feathers grown during different parts of the non-breeding season. Elucidating the overwintering overlap along spatial and isotopic niche axes for these three alcid species increases our understanding of potential interspecific interactions during a formerly understudied phase of the annual cycle, thereby enhancing our ability to predict seabird responses to varying environmental conditions.

**Authors:**

Emily Runnells¹, Gail Davoren¹

¹University of Manitoba

Non-breeding niche overlap of three North Atlantic alcid species

**Abstract:**

In colonial seabirds, ecological divergence may occur in the absence of physical barriers, driven by the isolation of populations due to distance, or the adaptation to local environment. In migratory seabirds, the geographic segregation among breeding populations can persist year round (i.e., strong migratory connectivity) when populations breeding separately do not mix outside the breeding area either, segregating in different non-breeding grounds. This migratory connectivity can exacerbate the isolation among populations, and thus influence the genetic structure among them. We have studied the non-breeding ecological niche and the migratory connectivity among 34 colonies of three Calonectris taxa, Scopoli's (C. diomedea), Cory's (C. borealis), and Cape Verde (C. edwardsii) shearwaters (805 breeding adults in total). To understand at what spatial scale migratory connectivity and preferences in non-breeding environment operate, and whether they are favouring ecological divergence among populations, we calculated migratory connectivity and non-breeding environmental niche at a colony, population and taxa level. To define populations, we grouped colonies in distance-based groups formed by the colonies that fell within buffers of increasing radius. At a taxa level, we found ecological segregation among the three taxa, with a clear spatial segregation between Scopoli's shearwaters and the other two taxa. At a colony level, we found low migratory connectivity among colonies of both Cory's and Scopoli's shearwaters, indicating high degree of individual mixing in the non-breeding areas. However, when we grouped the colonies in distance-based populations, the migratory connectivity increased, and differing environmental preferences appeared among populations, indicating the presence of some spatial structure at a population level. Our results agree with an ecological and evolutionary segregation among Cory's, Scopoli's and Cape Verde shearwaters, highlighting the role of migratory connectivity in the process of genetic divergence of populations across a landscape without physical barriers.

**Authors:**

Virginia Morera-Pujol¹, Paulo Catry², Maria Magalhães³, Clara Péron⁴, José Manuel Reyes-González⁵, José Pedro Granadeiro⁶, Teresa Militão⁵, Maria Dias⁷, Daniel Oro⁸, Giacomo Dell'Omo⁹, Martina Müller¹⁰, Vítor Paiva¹¹, Benjamin Metzger¹², Verónica Neves¹³, Joan Navarro¹⁴, Georgios Karris¹⁵, Stavros Xirouchakis¹⁶, Jacopo Cecere¹⁷, Ángel Sallent¹⁸, Manuela Forero¹⁹, Fernanda de Felipe¹, Zuzana Zajková¹, Marta Cruz-Flores¹, David Grémillet²⁰, Jacob González-Solís¹, Raül Ramos¹

¹Universitat de Barcelona, ²ISPA-Instituto Universitário, ³Regional Secretariat for the Sea, Science and Technology, Regional Directorate for Sea Affairs (DRAM, ⁴Université de Montpellier, ⁵nstitut de Recerca de la Biodiversitat (IRBio) and Departament de Biologia Evolutiva, Ecologia i Ciè, ⁶Universidade de Lisboa, ⁷BirdLife International, ⁸IMEDEA (CSIC-UIB) and Centre d'Estudis Avançats de Blanes (CSIC), ⁹Ornis Italica, ¹⁰Nagoya University, ¹¹University of Coimbra, ¹²BirdLife Malta, ¹³Universidade das Azores, ¹⁴Institut de Ciències del Mar, CSIC, ¹⁵Ionian University, ¹⁶University of Crete & Natural History Museum of Crete, ¹⁷Istituto Superiore per la Protezione e la Ricerca Ambientale (ISPRA), ¹⁸University of Murcia, ¹⁹Estación Biológica de Doñana CSIC, ²⁰University of Cape Town

Speciation and ecological divergence in three closely related shearwater taxa: insights from migratory connectivity and non-breeding habitat

**Abstract:**

The grey-faced petrel Pterodroma gouldi is endemic to the North Island of New Zealand. Although not threatened overall, this species is only abundant at a few sites, and in very small declining populations at most other sites. Causes for decline can be varied, but are generally introduced mammal predation or changes in oceanographic conditions. Independently of predation, marked variation in chick development and breeding success has been observed among colonies, particularly between those located along the East and the West coasts, and among years. We investigated the role played by adult foraging strategy, oceanographic conditions and predation in the variation of these breeding performances. East coast colonies were monitored for breeding performances during the 2011, 2012 and 2015 breeding seasons. Both East and West coast colonies were monitored for breeding success and chick development as well as for adult foraging strategy during the 2013 and 2014 breeding seasons. We deployed GPS devices to identify foraging areas, determined the frequency of chick feeding and adult foraging trip duration, and evaluated trophic position by stable isotope analyses of adult and chick diet and their prey. We found that grey-faced petrels breeding on the East coast tended to travel further from their breeding ground to feed, foraging for a longer period and thus fed their chicks less frequently. Stable isotope analyses revealed different δ15N and δ13C values between East and West coast breeders suggesting the use of different trophic levels and foraging habitats during chick rearing. Oceanographic conditions affected chick growth while predation by introduced mammals strongly impacted breeding success. An understanding of seabird diet and foraging strategy informs their conservation and management, as monitoring seabird trophic niche dimensions, foraging areas and reproductive parameters can reveal causes for population declines.

**Authors:**

Karen Bourgeois¹, Jemma Welch², Sylvain Dromzée³, Rob Dunn⁴, Megan Friesen⁵, Matt Rayner⁶, Graeme Taylor², James Russell⁴

¹Expertise Conservation des Oiseaux Marins et de la Biodiverité Insulaire (ECOMBI), ²Department of Conservation, ³Office Français de la Biodiversité, ⁴University of Auckland, ⁵Saint Martin's University, ⁶Auckland Museum

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