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Many pelagic seabirds moult their feathers while at sea, which is an energetically costly behaviour. Mortality rates during moult can be high, so spatial and trophic ecology during this critical period is important for understanding demographic patterns. Unfortunately, individual foraging behaviours specifically linked to at-sea moulting are commonly unclear. This paper combines 2 different approaches to geolocation: data from bird-borne geolocation loggers and stableisotope assignment using carbon and nitrogen isotope maps (isoscapes). Coupling 2 geolocation processes allows some uncertainties associated with isotope-based assignment to be constrained. We applied this approach to quantify species-specific foraging locations and individual trophic variability during feather regrowth in 3 sympatric auk populations breeding on the Isle of May, Scotland (common guillemot Uria aalge, razorbill Alca torda and Atlantic puffin Fratercula arctica). Inferred foraging areas during moult differed between species and feather types. Guillemots likely underwent moult within the southern North Sea, razorbills along the east coast of England and into the southern North Sea and puffins off the east coast of Scotland. Estimates of individual trophic position varied considerably within feather types (up to 1 trophic level difference between individuals), among feather types grown during different time periods and across the 3 species, with guillemots consistently foraging at higher trophic positions than razorbills and puffins. Used in combination, these methods better constrain foraging areas during moulting, and provide a technique to explore individual differences and flexibility in foraging strategy, which is valuable information for both seabird conservation and marine spatial planning.

The Atlantic puffin (Fratercula arctica) is a seabird species characterized by great diving capabilities and transoceanic migratory behavior. These movements contribute to the dispersion of the species during migration, and episodes of mortality associated with migration may be a normal event in the dynamic of the Atlantic puffin populations. This study aimed to describe the anatomopathological findings of an unusual mortality event of Atlantic puffins observed during the non-breeding period along the coast of the Canary Islands. The most consistent gross finding during necropsy was generalized muscle atrophy and fat depletion. The main histological findings were centered in the urinary tract, with dilation and inflammation of the primary ureter branch and medullary cones, and intraluminal trematodes identified as Renicola sloanei based on morphology and molecular analysis. Influenza virus infection was ruled out. The postmortem investigations performed in this mortality event of Atlantic puffins indicate that the animals were severely emaciated and suffered from nephropathy. The etiopathological investigation performed in relation to this mortality event of Atlantic puffins indicates starvation associated with bad weather conditions during migratory movement as the most likely cause of the unusual mortality event.

In the winter of 2022–2023, hundreds of the Atlantic puffins (Fratercula arctica) appeared dead in the coast of the Canary Islands, a rare event considering their cold-living habits, normally occupying the North Atlantic Ocean. In this work, investigation about the parasites present in the Atlantic puffins found in the biggest islands of the Archipelago was carried out from a population portion. Necropsies of 39 birds were made and, during the examination of the urinary tracts, helminths were found. Morphoanatomical analysis under microscope allowed to identify them into Renicola genus with high similarity to Renicola sloanei. After that, DNA was extracted and NADH dehydrogenase subunit 1 gene were amplificated by a polymerase chain reaction method followed by sequencing and phylogenetic analysis. The molecular results demonstrated that in fact R. sloanei was the helminth parasite present in the urinary tracts of the Atlantic puffins found in the Canary Islands.

In long-lived monogamous animals, pair bond strength and durability are usually associated with higher fitness. However, whether pairs maximise fitness during the non-breeding season by maintaining contact during the winter or, instead, prioritise individual condition is unclear. Using geolocators recording spatial (light) and behavioural (immersion) data, we tracked pairs of the long-term monogamous Atlantic puffin Fratercula arctica during the non-breeding season to determine whether and how migratory strategies were related to future pair breeding performance and whether within-pair similarity in migratory movements or individual behaviour best predicted future fitness. While pair members migrated separately, their routes were similar in the first part of the non-breeding season but diverged later on; nonetheless, pairs showed synchrony in their return to the breeding colony in spring. Pairs following more similar routes bred earlier and had a higher breeding success the following spring. However, female (but not male) winter foraging effort was also a strong predictor of subsequent fitness, being associated with future timing of breeding and reproductive success. Overall, females had higher daily energy expenditure than males, especially in the late winter when their route diverged from their partner’s and they foraged more than males. Our study reveals that female winter foraging, probably linked to pre-breeding condition, may be more critical for fitness than maintaining the pair bond outside of the breeding season. However, even without contact between mates, pairs can benefit from following similar migration routes and synchronise their returns, but the mechanisms linking these processes remain unclear.

The Atlantic puffin is a medium-sized seabird with black and white plumage and orange feet. It is distributed mainly along the northern Atlantic Ocean, and due, among other reasons, to human activities, it is in a threatened situation and classified as a vulnerable species according to the International Union of Conservation of Nature (IUCN). In this study, we used a total of 20 carcasses of juvenile Atlantic puffins to perform MRI, as well as anatomical cross-sections. Thus, an adequate description of the head was made, providing valuable information that could be helpful as a diagnostic tool for veterinary clinicians, who increasingly treat these birds in zoos, rehabilitation centers, and even in the wild.

Demographic correlations are pervasive in wildlife populations and can represent important secondary drivers of population growth. Empirical evidence suggests that correlations are in general positive for long-lived species, but little is known about the degree of variation among spatially segregated populations of the same species in relation to environmental conditions. We assessed the relative importance of two cross-season correlations in survival and productivity, for three Atlantic puffin (Fratercula arctica) populations with contrasting population trajectories and non-overlapping year-round distributions. The two correlations reflected either a relationship between adult survival prior to breeding on productivity, or a relationship between productivity and adult survival the subsequent year. Demographic rates and their correlations were estimated with an integrated population model, and their respective contributions to variation in population growth were calculated using a transient-life table response experiment. For all three populations, demographic correlations were positive at both time lags, although their strength differed. Given the different year-round distributions of these populations, this variation in the strength population-level demographic correlations points to environmental conditions as an important driver of demographic variation through life-history constraints. Consequently, the contributions of variances and correlations in demographic rates to population growth rates differed among puffin populations, which has implications for—particularly small—populations' viability under environmental change as positive correlations tend to reduce the stochastic population growth rate.

Examining contaminant concentrations in birds in Arctic environments is important for managing species for assessing long-term trends. Recent reports on mercury (Hg) concentrations in Arctic species of seabirds has identified a need for data from missing regions or species. We measured arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb), manganese (Mn), Hg and selenium (Se) in the body feathers of Atlantic Puffin (Fratercula arctica) from four colonies in Iceland in 2011 and one in 2009. Puffins forage on small fish at an intermediate trophic concentration. We found that (1) concentrations examined in the colony in 2009 were lower than in 2011 for all metals except As and Hg, and (2) concentrations of Cd and Se varied significantly among colonies for feathers collected in 2011. Pb concentrations in Puffin feathers in one colony were 14-fold higher in 2009 than in 2011 (mean of 805 ng.g−1 vs. 58 ng.g−1). The highest mean Hg concentration in 2011 was 362 ng.g−1 and was 4880 ng.g−1 for Se. The concentrations of Hg in the Atlantic Puffins reported in this study were similar to, or lower than those reported for the same species elsewhere and for Tufted Puffin from the Pacific.

Background Fidelity to a given foraging location or route may be beneficial when environmental conditions are predictable but costly if conditions deteriorate or become unpredictable. Understanding the magnitude of fidelity displayed by different species and the processes that drive or erode it is therefore vital for understanding how fidelity may shape the demographic consequences of anthropogenic change. In particular, understanding the information that individuals may use to adjust their fidelity will facilitate improved predictions of how fidelity may change as environments change and the extent to which it will buffer individuals against such changes. Methods We used movement data collected during the breeding season across eight years for common guillemots, Atlantic puffins, razorbills, and black-legged kittiwakes breeding on the Isle of May, Scotland to understand: (1) whether foraging site/route fidelity occurred within and between years, (2) whether the degree of fidelity between trips was predicted by personal foraging effort, and (3) whether different individuals made more similar trips when they overlapped in time at the colony prior to departure and/or when out at sea suggesting the use of the same local environmental cues or information on the decisions made by con- and heterospecifics. Results All species exhibited site and route fidelity both within- and between-years, and fidelity between trips in guillemots and razorbills was related to metrics of foraging effort, suggesting they adjust fidelity to their personal foraging experience. We also found evidence that individuals used local environmental cues of prey location or availability and/or information gained by observing conspecifics when choosing foraging routes, particularly in puffins, where trips of individuals that overlapped temporally at the colony or out at sea were more similar. Conclusions The fidelity shown by these seabird species has the potential to put them at greater risk in the face of environmental change by driving individuals to continue using areas being degraded by anthropogenic pressures. However, our results suggest that individuals show some flexibility in their fidelity, which may promote resilience under environmental change. The benefits of this flexibility are likely to depend on numerous factors, including the rapidity and spatial scale of environmental change and the reliability of the information individuals use to choose foraging sites or routes, thus highlighting the need to better understand how organisms combine cues, prior experience, and other sources of information to make movement decisions.

Atlantic Puffin (Fratercula arctica) chick growth, diet, feeding rate and early survival and adult body condition were quantified on Hornøya, North Norway in 2002 and 2003 after a long-term change in diet from large Capelin (Mallotus villosus) and Sand Lance (Ammodytes spp.) in the early 1980s to smaller, poorer quality gadids, Sand Lance and Herring (Clupea harengus). The results were compared with data collected in 1980-1982, when feeding conditions were considered very favourable. Chick growth was similar in both periods. The breeding adults compensated for reduced food quality by increasing the feeding frequency, such that the chicks received the same amount of fish (g d-1 and kJ d-1) or even more in 2002-2003. This increase in activity did not, however, result in a decline in adult body mass, suggesting that prey were abundant close to the colony and that the parents did not suffer from the apparent increased feeding effort.