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Flexible migratory choices of Cory’s shearwaters are not driven by shifts in prevailing air currents

Publication . Dell’Ariccia, Gaia; Benhamou, Simon; Dias, Maria P.; Granadeiro, José Pedro; Sudre, Joel; Catry, Paulo; Bonadonna, Francesco

Wind conditions strongly affect migratory costs and shape flyways and detours for many birds, especially soaring birds. However, whether winds also influence individual variability in migratory choices is an unexplored question. Cory's shearwaters (Calonectris borealis) exhibit migratory flexibility, changing non-breeding destination across the Atlantic Ocean within and between years. Here, we investigated how wind dynamics affect the spatiotemporal migratory behaviour and whether they influence individual choices of non-breeding destination. We analysed 168 GLS tracks of migratory Cory's shearwaters over five years in relation to concurrent wind data. We found no evidence for an association of the use of specific paths or destinations with particular wind conditions. Our results suggest that shearwaters deliberately choose their non-breeding destination, even when the choice entails longer distances and higher energetic costs for displacement due to unfavourable wind conditions en route. Favourable winds trigger migration only when directed towards specific areas but not to others. Despite their dependence on wind for dynamic soaring, Cory's shearwaters show a high individuality in migratory behaviour that cannot be explained by individual birds encountering different meteorological conditions at departure or during migratory movements.

2018Journal article

Open access

Seabird diet analysis suggests sudden shift in the pelagic communities of the subtropical Northeast Atlantic

Publication . Romero, Joana; Catry, Paulo; Alonso, Hany; Granadeiro, José Pedro

The dynamics of the subtropical pelagic ecosystems of the Northeast Atlantic are still poorly known due to the high costs associated with sampling large oceanic areas. Top predators can be used as alternative low-cost samplers and indicators of the temporal variability of such systems. To study the variation in the composition of pelagic species through time in the broad Canary current region, we analysed foraging trips and regurgitations of Cory's shearwaters Calonectris borealis nesting on Selvagens islands, in 2008-2011 and 2016-2018. Fisheries data, oceanographic variables and the North Atlantic Oscillation were explored as possible explanatory variables for trends in behaviour and diet. Cory's shearwaters' diet, complemented by fisheries data, revealed marked changes in the composition of the pelagic fish communities. In 2016 there was a peak in the abundance of the Atlantic chub mackerel Scomber colias, followed by an explosive increase in the abundance of the Longspine snipefish Macroramphosus scolopax in 2017 and 2018, as deduced from the diet composition of the Cory's shearwater, and supported by fisheries data, in the broad oceanic area surrounding the Selvagens islands. Oceanographic variables did not show fluctuations correlated with these marked shifts in pelagic fish availability, the causes of which remain largely unknown. This study highlights the importance of the Atlantic chub mackerel and of the Longspine snipefish in the Madeira/Canary region and exemplifies the efficiency of avian predators in revealing rapid changes in pelagic communities of oceanic domains. Such trends and variations need to be better monitored and understood to measure the impact of ongoing global changes and to sustainably manage the marine environment and resources.

2021Journal article

Open access

Untangling causes of variation in mercury concentration between flight feathers

Publication . Gatt, Marie C.; Furtado, Ricardo Andrade; Granadeiro, José P.; Lopes, Daniel; Pereira, Eduarda; Catry, Paulo

Bird feathers are one of the most widely used animal tissue in mercury biomonitoring, owing to the ease of collection and storage. They are also the principal excretory pathway of mercury in birds. However, limitations in our understanding of the physiology of mercury deposition in feathers has placed doubt on the interpretation of feather mercury concentratoins. Throughout the literature, moult sequence and the depletion of the body mercury pool have been taken to explain patterns such as the decrease in feather mercury from the innermost (P1) to the outermost primary feather (P10) of the wing. However, it has been suggested that this pattern is rather a measurement artefact as a result of the increased feather mass to length ratio along the primaries, resulting in a dilution effect in heavier feathers. Here, we attempt to untangle the causes of variation in feather mercury concentrations by quantifying the mercury concentration as μg of mercury (i) per gram of feather, (ii) per millimetre of feather, and (iii) per day of feather growth in the primary feathers of Bulwer's Petrel Bulweria bulwerii chicks, effectively controlling for some of the axes of variation that may be acting in adults, and monitoring the growth rate of primary feathers in chicks. The mercury concentration in Bulwer's Petrel chicks' primaries increased from the innermost to the outermost primary for all three concentration measures, following the order of feather emergence. These observations confirm that the pattern of mercury concentration across primary feathers is not an artefact of the measure of concentration, but is likely an effect of the order of feather growth, whereby the earlier grown feathers are exposed to higher blood mercury concentrations than are later moulted feathers as a result of blood mercury depletion.

2021Journal article

Open access

Methods to detect spatial biases in tracking studies caused by differential representativeness of individuals, populations and time

Publication . Pujol, Virginia Morera; Catry, Paulo; Magalhães, Maria; Peron, Clara; Reyes‐González, José Manuel; Granadeiro, José P.; Militão, Teresa; Dias, Maria P.; Oro, Daniel; Dell'Omo, Giacomo; Müller, Martina; Paiva, Vitor H.; Metzger, Benjamin; Neves, V C; Navarro, Joan; Karris, Georgios; Xirouchakis, Stavros; Cecere, Jacopo G.; Zamora‐López, Antonio; Forero, Manuel G.; Ouni, Ridha; Romdhane, Mohamed Salah; De Felipe, Fernanda; Zajková, Zuzana; Cruz‐Flores, Marta; Grémillet, David; González‐Solís, Jacob; Ramos, Raül

Aim Over the last decades, the study of movement through tracking data has grown exceeding the expectations of movement ecologists. This has posed new challenges, specifically when using individual tracking data to infer higher-level distributions (e.g. population and species). Sources of variability such as individual site fidelity (ISF), environmental stochasticity over time, and space-use variability across species ranges must be considered, and their effects identified and corrected, to produce accurate estimates of spatial distribution using tracking data. Innovation We developed R functions to detect the effect of these sources of variability in the distribution of animal groups when inferred from individual tracking data. These procedures can be adapted for their use in most tracking datasets and tracking techniques. We demonstrated our procedures with simulated datasets and showed their applicability on a real-world dataset containing 1346 year-round migratory trips from 805 individuals of three closely related seabird species breeding in 34 colonies in the Mediterranean Sea and the Atlantic Ocean, spanning 10 years. We detected an effect of ISF in one of the colonies, but no effect of the environmental stochasticity on the distribution of birds for any of the species. We also identified among-colony variability in nonbreeding space use for one species, with significant effects of population size and longitude. Main conclusions This work provides a useful, much-needed tool for researchers using animal tracking data to model species distributions or establish conservation measures. This methodology may be applied in studies using individual tracking data to accurately infer the distribution of a population or species and support the delineation of important areas for conservation based on tracking data. This step, designed to precede any analysis, has become increasingly relevant with the proliferation of studies using large tracking datasets that has accompanied the globalization process in science driving collaborations and tracking data sharing initiatives.

2022Journal article

Open access

Spatial scales of marine conservation management for breeding seabirds

Publication . Oppel, Steffen; Bolton, Mark; Carneiro, Ana Paula B.; Dias, Maria P.; Green, Jonathan A.; Masello, Juan F.; Phillips, Richard A.; Owen, Ellie; Quillfeldt, Petra; Beard, Annalea; Bertrand, Sophie; Blackburn, Jez; Boersma, P. Dee; Borges, Alder; Broderick, Jess; Catry, Paulo; Cleasby, Ian; Clingham, Elizabeth; Creuwels, Jeroen; Crofts, Sarah; Cuthbert, Richard J.; Dallmeijer, Hanneke; Davies, Delia; Davies, Rachel; Dilley, Ben J.; Dinis, Herculano; Dossa, Justine; Dunn, Michael J; Efe, Marcio A.; Fayet, Annette; Figueiredo, Leila; Frederico, Adelcides Pereira; Gjerdrum, Carina; Godley, Brendan J.; Granadeiro, José Pedro; Guilford, Tim; Hamer, Keith C.; Hazin, Carolina; Hedd, April; Henry, Leeann; Hernández-Montero, Marcos; Hinke, Jefferson; Kokubun, Nobuo; Leat, Eliza; Tranquilla, Laura McFarlane; Metzger, Benjamin; Militão, Teresa; Montrond, Gilson; Mullié, Wim; Padget, Oliver; Pearmain, Elizabeth J.; Pollet, Ingrid L.; Pütz, Klemens; Quintana, Flavio; Ratcliffe, Norman; Ronconi, Robert A.; Ryan, Peter G.; Saldanha, Sarah; Shoji, Akiko; Sim, Jolene; Small, Cleo; Soanes, Louise; Takahashi, Akinori; Trathan, Phil; Trivelpiece, Wayne; Veen, Jan; Wakefield, Ewan; Weber, Nicola; Weber, Sam; Zango, Laura; Daunt, Francis; Ito, Motohiro; Harris, Michael P.; Newell, Mark A.; Wanless, Sarah; González-Solís, Jacob; Croxall, John

Knowing the spatial scales at which effective management can be implemented is fundamental for conservation planning. This is especially important for mobile species, which can be exposed to threats across large areas, but the space use requirements of different species can vary to an extent that might render some management approaches inefficient. Here the space use patterns of seabirds were examined to provide guidance on whether conservation management approaches should be tailored for taxonomic groups with different movement characteristics. Seabird tracking data were synthesised from 5419 adult breeding individuals of 52 species in ten families that were collected in the Atlantic Ocean basin between 1998 and 2017. Two key aspects of spatial distribution were quantified, namely how far seabirds ranged from their colony, and to what extent individuals from the same colony used the same areas at sea. There was evidence for substantial differences in patterns of space-use among the ten studied seabird families, indicating that several alternative conservation management approaches are needed. Several species exhibited large foraging ranges and little aggregation at sea, indicating that area-based conservation solutions would have to be extremely large to adequately protect such species. The results highlight that short-ranging and aggregating species such as cormorants, auks, some penguins, and gulls would benefit from conservation approaches at relatively small spatial scales during their breeding season. However, improved regulation of fisheries, bycatch, pollution and other threats over large spatial scales will be needed for wide-ranging and dispersed species such as albatrosses, petrels, storm petrels and frigatebirds.

2018Journal article

Restricted access