United States

**Abstract:**

Multi-colony studies showed that when large seabird colonies are spatially close to each other, segregation of foraging areas can often occur. We aimed at 1) characterizing the foraging behaviour of a Mediterranean procellariiform, the Scopoli&#39;s shearwater Calonectris diomedea; 2) investigating whether foraging segregation is used to reduce intraspecific competition between colonies in four adjacent islands of the Tuscan Archipelago (C Mediterranean, Italy). The reconstructed GPS routes of 26 breeding birds from the islands of Giannutri (No. breeding pairs 80-145), Cerboli (50-85), Pianosa (150-250) and Argentarola (35-50) were analysed during the chick rearing period, identifying the main behavioural patterns (resting, travelling, foraging) though a segmentation analysis (EMbC). Foraging areas were identified by means of the Kernel Density Estimation (KDE) and the Local Convex Hull (LoCoH) methods, applied on the locations categorized as foraging. The presence of foraging segregation among colonies was investigated using a hierarchical clustering on the utilization distribution overlap between individuals. As expected, LoCoH estimated smaller foraging areas with less portions of mainland included than KDE (mean difference KDE-LoCoH: 1125.75 km2, CI: 773.86 - 1477.63 km2), indicating that the former method could better perform than standard KDE in seabird studies. All tracked birds nesting on Pianosa foraged close to the island (LoCoH mean ± SD: 769 ± 308 km2), while individuals from other colonies explored wider areas (1615 ± 780 km2). Overall, individual foraging behaviour was similar within colonies, showing spatial segregation among colonies. The highest level of segregation was observed between birds from Pianosa and Giannutri, that formed two distinct clusters using non-overlapping foraging areas. This multi-colonies study provides information about the habitat use in foraging behaviour of Scopoli&#39;s shearwaters and seems to confirm the segregation of foraging areas among neighbouring colonies.

**Authors:**

Elisa Simi¹, Nicola Baccetti², Francesca Giannini³, Dimitri Giunchi¹, Camilla Gotti⁴, Francesco Pezzo⁴, Enrica Pollonara⁵, Lorenzo Vanni¹, Marco Zenatello⁴, Giulia Cerritelli¹

¹Department of Biology, University of Pisa, ²Ozzano dell&#39;Emilia, ³Arcipelago Toscano National Park, ⁴ISPRA (Italian Institute for Environmental Protection and Research), ⁵Centro Ornitologico Toscano

3rd World Seabird Conference

Small-scale foraging segregation in breeding Scopoli&#39;s shearwater

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:**

Multi-colony studies showed that when large seabird colonies are spatially close to each other, segregation of foraging areas can often occur. We aimed at 1) characterizing the foraging behaviour of a Mediterranean procellariiform, the Scopoli's shearwater Calonectris diomedea; 2) investigating whether foraging segregation is used to reduce intraspecific competition between colonies in four adjacent islands of the Tuscan Archipelago (C Mediterranean, Italy). The reconstructed GPS routes of 26 breeding birds from the islands of Giannutri (No. breeding pairs 80-145), Cerboli (50-85), Pianosa (150-250) and Argentarola (35-50) were analysed during the chick rearing period, identifying the main behavioural patterns (resting, travelling, foraging) though a segmentation analysis (EMbC). Foraging areas were identified by means of the Kernel Density Estimation (KDE) and the Local Convex Hull (LoCoH) methods, applied on the locations categorized as foraging. The presence of foraging segregation among colonies was investigated using a hierarchical clustering on the utilization distribution overlap between individuals. As expected, LoCoH estimated smaller foraging areas with less portions of mainland included than KDE (mean difference KDE-LoCoH: 1125.75 km2, CI: 773.86 - 1477.63 km2), indicating that the former method could better perform than standard KDE in seabird studies. All tracked birds nesting on Pianosa foraged close to the island (LoCoH mean ± SD: 769 ± 308 km2), while individuals from other colonies explored wider areas (1615 ± 780 km2). Overall, individual foraging behaviour was similar within colonies, showing spatial segregation among colonies. The highest level of segregation was observed between birds from Pianosa and Giannutri, that formed two distinct clusters using non-overlapping foraging areas. This multi-colonies study provides information about the habitat use in foraging behaviour of Scopoli's shearwaters and seems to confirm the segregation of foraging areas among neighbouring colonies.

**Authors:**

Elisa Simi¹, Nicola Baccetti², Francesca Giannini³, Dimitri Giunchi¹, Camilla Gotti⁴, Francesco Pezzo⁴, Enrica Pollonara⁵, Lorenzo Vanni¹, Marco Zenatello⁴, Giulia Cerritelli¹

¹Department of Biology, University of Pisa, ²Ozzano dell'Emilia, ³Arcipelago Toscano National Park, ⁴ISPRA (Italian Institute for Environmental Protection and Research), ⁵Centro Ornitologico Toscano

Small-scale foraging segregation in breeding Scopoli's shearwater

poster

**Abstract:**

Marine visual seabirds rely on waters with clear visibility to forage. A single-acute increase in turbidity may not have a severe effect on finding prey. However, extended periods of turbidity can impact the foraging success of predators. Long-lasting turbidity created by a large-scale shipping channel dredging proposed at the mouth of the Yarra river, Australia, could potentially affect the foraging and breeding success of ~35,000 little penguins Eudyptula minor. We conducted three-dimensional spatial studies using GPS or satellite trackers, and time-depth recorders, to examine the underwater habitat preferences of the penguins within the dredging area. Our data showed that 39% of feeding dives were within the shipping channels. Given the potential negative effect, penguins were used as key indicators in a four-year monitoring plan during the dredging. We used a penguin monitoring system equipped with a weighing platform to monitor body mass change to assure that penguin weights would not drop below a critical threshold. Fortunately, this critical threshold was not reached during dredging. Outside the dredging period, we used oceanographic data from a Ship of Opportunity (volunteer merchant vessels carrying environmental sensors) to assess the fine-scale habitat use of the little penguin within the estuarine plume. We compared the home-range (transit and foraging) and core-range (foraging hotspot within the home-range) with the environmental conditions in the accessible, but not visited range (i.e. non-foraging range). Waters in the core foraging range were less turbid but also less productive and dynamic. Even under unfavourable conditions, penguins spent a great proportion of their time in the core-ranges. Although less productive, these low turbidity waters may improve the ability of penguins to detect and capture their prey. Our results highlight that a visual predator selectively forages in waters with better visibility but less productive as a potential means to improve foraging efficiency.

**Authors:**

Nicole Kowalczyk¹, Richard Reina¹, Tiana Preston¹, Yan Ropert-Coudert², Akiko Kato², Andre Chiaradia³

¹School of Biological Sciences, Monash University, ²Centre d'Etudes Biologiques de Chizé, CNRS, ³Phillip Island Nature Parks

Foraging habitat preference of an inshore seabird within estuarine plume fronts

**Abstract:**

Temporal variations in the numbers of foraging seabirds usually coincide with concurrent variations in physical processes influencing prey availability. Responses to periodic tidal currents are commonly reported, with certain tidal states being favoured. By contrast, responses to intermittent meteorological events have rarely been reported, even though wind-driven exchanges of water masses or intrusion of estuarine plumes could have similar consequences. This study compares responses of foraging seabirds to physical processes in the Ria de Vigo, north-western Spain. The numbers of foraging European shags Phalacrocorax aristotellis and yellow-legged gulls Larus michahellis showed no response to variations in current direction/speed. By contrast, the numbers of both species increased during the intrusion of the Western Iberian Buoyant Plume following high freshwater discharge and southerly winds. The differences in responses to periodic tidal currents and intermittent meteorological events presumably relate to their relative control of conditions in the ria; whilst currents cannot be considered particularly weak, intermittent weather events have a stronger control on conditions. These findings show that responses to periodic tidal currents could be absent or subdued when intermittent meteorological events have a greater control on conditions, even though periodic tidal currents are conspicuous physical processes in coastal environments.

**Authors:**

James Waggitt¹, Shaun Fraser², Ricardo Torres³

¹Bangor University, ²University of Highlands and Islands, ³Plymouth Marine Laboratory

Foraging seabirds respond to an intermittent meteorological event in the Ria de Vigo, Spain.

**Abstract:**

The Columbia River on the west coast of the United States is the 21st largest river in the world in terms of annual mean flow. Freshwater discharge from the Columbia River flows into the northern California Current Ecosystem, one of the most productive marine food webs in the world. A large, dynamic plume is formed at the mouth of the river, which has a strong regional influence on nearshore oceanography and productivity. Using at-sea surveys, land-based surveys, and satellite telemetry, we demonstrated that the plume also strongly affects the distribution, abundance, and habitat preferences of seabirds and seabird prey. Specifically, we found that two numerically dominant piscivorous seabirds, common murres (Uria aalge) and sooty shearwaters (Ardenna grisea), aggregate in large numbers in this region, preferentially select plume habitat, and respond to spatial and temporal changes in plume dynamics. Coastal pelagic fishes consumed by seabirds such as northern anchovy (Engraulis mordax) are disproportionately more abundant in plume waters compared to adjacent waters, suggesting that foraging birds use the plume to increase prey encounter probabilities. Plume effects are evident in both summer and winter, although the dynamics driving winter use of the plume are not well-understood. Given predicted changes in freshwater runoff with climate change, and high levels of human use of the Columbia River and other large rivers for commercial and recreational activities, we suggest that river plumes are under-appreciated regions of global conservation importance for seabirds.

**Authors:**

Jeannette Zamon¹, Elizabeth Phillips², Josh Adams³

¹NOAA Fisheries - Pt. Adams Research Station, ²NOAA Fisheries - Northwest Fisheries Science Center, ³US Geological Survey

Using seabird associations with the Columbia River Plume to demonstrate the conservation importance of river plumes

**Abstract:**

Here we describe the seabird assemblage recorded adjacent to the Amazon River mouth, the greatest freshwater input in the marine environment globally, in North Brazil. Through two ship-based surveys conducted between March and May 2015, 219 seabird counts were carried out (118 during navigation and 101 point-counts). A total of 443 individuals of 21 species were recorded. The species composition was almost all migrant taxa from both the Northern and Southern Hemispheres. Associations between bird assemblages (grouped by seabird families) and environmental variables were accessed through univariate, two-part multiple regression models and canonical correspondence analysis. Seabirds aggregate in two main areas, each related to different mesoscale oceanographic features: the tidal mixing and saline front at the mouth of the Amazon River and the ring-formation zone on the border with French Guiana. For Procellariidae and Hydrobatidae, associations with sea surface temperature and distance from the coast were important. These groups were mainly observed in the ring-formation zone, which entraps Amazon River water in the core of the rings, and storm-petrels also occurred at the 20-m isobath, where the advection process carries river' waters to the surface causing local zooplankton enhancement. On the other hand, for Sternidae, Laridae and Stercorariidae, chlorophyll-a and bathymetry were the most important factors. Their distributions were associated with the mouth of the Amazon River, where primary productivity is high. The oceanographic characteristics of these aggregation zones make them ecologically important areas for meso- and megafaunal marine taxa, particularly seabirds.

**Authors:**

Nicholas Daudt¹, Suzana Martins¹, Eduardo Kirinus¹, Leandro Bugoni¹

¹Universidade Federal do Rio Grande - FURG

Seabird assemblage at the mouth of the world's largest river, the Amazon River

**Abstract:**

Seabirds, particularly Procellariiformes, are known to harbour a rich community of ectosymbionts, including fleas, lice, ticks, blood-feeding mites, feather mites and hippoboscid flies. Among them, feather mites (Acariformes: Astigmata: Analgoidea and Pterolichoidea) are the most abundant and diverse group of permanent symbionts living on the body of birds. Although feather mite species richness seems to be particularly high on seabirds as in other groups of aquatic birds, it is still poorly known, with a high potential to discover new species. In this study we investigated the feather mite fauna of the European storm-petrel, Hydrobates pelagicus (Procellariiformes: Hydrobatidae) nesting in the north-east Atlantic Ocean and Mediterranean Sea. The acarological material was collected from 101 adult birds across eight breeding colonies using the dust-ruffling method. On this seabird host we found seven feather mite species belonging to five genera in three families, of which three corresponded to undescribed species. The family Avenzoariidae was represented by Zachvatkinia hydrobatidii and a new Rhinozachvatkinia species, the family Alloptidae was represented by 3 species of genus Brephosceles (B. pelagicus, B. longirostris and Brephosceles sp.) and a new Microspalax species, and the family Xolalagidae included Ingrassia oceanica. For most species, morphological identifications were confirmed by DNA barcode data on the mitochondrial cytochrome c oxidase subunit I gene (COI). Further steps of investigation would include description of the new discovered species of Brephosceles along with redescriptions of the other two species of Brephosceles. Overall, our results confirm the high diversity of ectosymbionts hosted by seabirds.

**Authors:**

Laura Stefan¹, Sergey Mironov², Jacob Gonzalez-Solis³, Andrei Mihalca⁴

¹National Institute of Research and Development for Biological Sciences, ²Zoological Institute, Russian Academy of Sciences, ³Universitat de Barcelona, ⁴University of Agricultural Sciences and Veterinary Medicine of Cluj-Napoca

Feather mite fauna of the European storm-petrel, Hydrobates pelagicus

**Abstract:**

Fishing discards are of great relevance to seabird trophic ecology worldwide. The Kelp Gull (Larus dominicanus) is a generalist and opportunistic species that feeds on a wide variety of prey obtained in natural and human-related environments. We analyzed the spatial association with operating coastal bottom trawl vessels and the contribution of discards to the diet of incubating individuals at Punta Tombo (44°02'S, 65°11'W), Argentina. Based on carbon and nitrogen isotopic values of whole blood samples from 22 and 20 adults in 2016 and 2017, respectively, Bayesian mixing model outputs showed that discards (demersal prey normally unavailable to surface feeding predators) were the main prey, with similar contribution in both years (2016 = 47 ± 4%; 2017 = 52 ± 5%), followed by mussels (Perumytilus purpuratus) (2016 = 29 ± 4%; 2017 = 24 ± 5%), and Argentine anchovy (Engraulis anchoita) (2016 = 14 ± 6%; 2017 = 14 ± 7%). We also tracked 14 and 13 of these incubating adults using GPS loggers during 2016 and 2017, recording 134 and 122 foraging tips, respectively. Linear mixed models showed no significant differences between years in the maximum distances from the colony, total distance traveled and duration of foraging trips. Open sea environments were the most visited in both seasons and included areas where fishing vessels were operating according to vessel monitoring system data. Fisheries discards were the main prey for most tracked individuals even for those who did not travel to fishing areas during the few days of the tracking period, indicating plasticity in individual feeding behavior likely in response to the differential availability of alternative prey. Our results show that discards generated by coastal trawl fisheries are an important diet component for incubating Kelp Gulls at Punta Tombo.

**Authors:**

Tatiana Kasinsky¹, Cristian Marinao¹, Nicolás Suárez¹, Pablo Yorio²

¹Centro de Estudio de Sistemas Marinos, CESIMAR-CONICET, Argentina, ²Centro de Estudio de Sistemas Marinos, CESIMAR-CONICET, Argentina. Wildlife Conservation Society Arg

Trophic ecology of incubating Kelp Gulls (Larus dominicanus) and its relationship with coastal trawl fisheries in northern Patagonia, Argentina

**Abstract:**

In several ocean regions, fisheries and seabirds compete for the same resource. In Peru, the anchovy (Engraulis ringens) is not only the most exploited resource for the industrial fishing but also the main food for endemic seabirds. This competition may result in interactions that negatively affect some species through incidental capture or food competition. We attached video cameras and GPS tags on 137 Peruvian boobies in two guano islands in northern Peru between November 2020 and may 2021 during the anchovy fishing season to determine the type of encounter and the percentage of interaction between seabirds and fisheries. The analysis of GPS tracks and the extension of the fishing zones of vessels extracted from the Global Fishing Watch platform revealed a high overlapping area. The magnitude of interactions varied across season and locations between 0% and 29%. The majority of the booby interacting with vessels plunged dive and feed inside the purse-seine nets. Although flocks of endemic and migratory seabirds in Peruvian waters regularly interact with minor and large scale fisheries, our study is the first in quantifying these interactions.

**Authors:**

Cinthia Irigoin-Lovera¹, CARLOS ZAVALAGA¹

¹Universidad Cientifica del Sur

First estimations of the magnitude of interactions between Peruvian boobies and the anchovy commercial fishing fleet

**Abstract:**

Breeding seabirds must balance foraging for themselves and feeding their chicks with the constraints imposed as central place foragers. We evaluated Magellanic penguin (Spheniscus magellanicus) adult and chick diets during the early and late chick rearing periods and assessed adult trophic consistency throughout the season for using carbon (δ13C) and nitrogen (δ15N) stable isotope values. We sampled blood cells (integrates information over months) and plasma (integrates information over weeks) from 13 families (adults and offspring) at Martillo Island colony, Beagle Channel, Argentina during early-chick rearing (ECR) and late-chick rearing (LCR) periods in 2016. Isotopic niche width was larger during ECR than LRC for both tissues in chicks and adults. From ECR to LCR we found a significant decrease in plasma δ13C values of chicks and adults (ΔC=0.5; 1.0 per mil respectively) and blood cell δ13C values for chicks only (ΔC=0.8 per mil). We also found a small decrease in plasma δ15N values for chicks and females (ΔN=0.4 per mil) and blood cell δ15N values for females only (ΔN=0.5 per mil), without any changes in males. Despite these statistical differences, we estimated similar trophic position (TPs) between ages and stages (TPs≈3). Within-family variability accounted for 90% of the total isotopic variability and we did not find any differential food provisioning during ECR or LCR in both tissues (Euclidean distance analysis). By comparing tissues with differing turnover rates we found slightly higher individual niche consistency in males relative to females. In conclusion, we found no evidence of differential provisioning by parents, which contrasts with studies in northern Patagonia were chicks had diets most similar to males during LCR. Differences observed in isotopic niches could be due to a differential dietary evenness over time and/or different areas used, but with the consumption of prey occupying same trophic level, since penguins showed consistency in their TPs across the season.

**Authors:**

Samanta Dodino¹, Luciana Riccialdelli¹, Michael Polito², Andrea Raya Rey¹

¹Centro Austral de Investigaciones Cientificas (CADIC-CONICET), ²Louisiana State University

Every family is a world: Offspring provisioning and individual trophic niche consistencies in Magellanic penguins

**Abstract:**

Skuas are scavengers in both marine and terrestrial environments, feeding on a variety of prey types and taking advantage of fishery discards. Little is known on the trophic ecology of the Brown Skua (Catharacta antarctica) breeding along the Patagonian coast, Argentina. To assess the interannual variation in the use of feeding areas during the incubation period and the possible spatial interaction with coastal trawl fisheries, a total of 24 global positioning system loggers were deployed on adults during the 2016 to 2018 breeding seasons. Skuas foraged mostly in open waters in the three study years. During 2016, birds travelled east of the colony (mean = 87.4º), reaching a maximum distance from the colony of 32.8 km (0.9-56.8; n = 10 birds and 108 trips) and covering over 1670 km2. During 2017 and 2018, birds travelled mainly northeast (38.7º and 37.9º, respectively) up to 61.2 km (1.1-109.52; n = 8 birds and 87 trips) and 48.7 km (1.3-97.48; n = 6 birds and 92 trips) from the colony, respectively. In both years birds used a larger total area than in 2016 (3094 and 3727 km2, respectively). During 2017 and 2018, tracked individuals used 70 and 81% of the area used in 2016, respectively. The operation of the coastal trawl fishery based in Rawson port, which consisted of 40 vessels, showed no overlap with foraging skuas in the three years, as changes in market demands and target species resulted in the northward movement of fishing activity. These results show a similar use of marine environments between years and the importance of waters surrounding the colony in the trophic ecology of the species. Results also suggest the need for further studies to assess the interaction between Brown Skuas and trawl fisheries, given the potential changes in the spatial pattern of fishing activity.

**Authors:**

Nicolás Suárez¹, Cynthia Ibarra¹, Pablo Yorio¹

¹Centro Nacional Patagónico - CONICET

Interannual variation in Brown Skua foraging areas and assessment of spatial interaction with trawl fisheries in coastal Patagonia, Argentina

**Abstract:**

Foraging is an efficient way to study the effects of environmental variability on marine top predators, as they integrate both direct effects through increased energetic costs at sea and indirect effects through modification of prey accessibility. Using a 19-year automated monitoring system of ~400 individuals (> 45,000 trips), we investigated short-term and interannual variability in foraging performances (trip duration and mass gain) of the little penguin (Eudyptula minor), an inshore seabird living in a climate change hotspot. We found marked seasonal patterns in foraging performances with clear optimum periods but no decrease along the breeding season. The advantage of being an early or late breeder within a season varied with the overall timing of the population breeding, showing a complex interplay between the individual and population scales. Although foraging was less variable at the inter-annual scale, we still highlighted three groups of low, average and good annual foraging performances in each breeding stage. Overall annual performances were affected mainly by late chick-rearing (i.e. post-guard), and low performances during this stage were associated with significantly lower breeding success than years of average or high foraging performances. To understand how the environment might explain such variability in foraging performances, we studied simultaneously the effect of currents, waves and tides, which might directly affect penguin costs at sea and the effects of productivity and vertical stratification, which might affect penguin foraging indirectly through a modification of prey availability. Short-term poor conditions in foraging (at the trip scale) were mostly associated with increased waves and currents and secondarily driven by a decreased and shallower stratification. These results show that short-term variations in the environment may be sufficient to affect seabird breeding significantly through foraging performances. Although these performances are often thought to depend on prey accessibility mainly, we showed the primary role of parameters directly affecting seabirds costs while at sea. Finally, a good synchrony between birds' phenology and primary production cycles explained high foraging performances at the inter-annual scale, highlighting the importance of animal phenology, a parameter known to be highly affected by climate change.

**Authors:**

Nicolas Joly¹, Andre Chiaradia², Jean-Yves Georges¹, Claire Saraux¹

¹CNRS, ²Phillips Island Nature Parks

Small-scale foraging segregation in breeding Scopoli's shearwater

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