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Individual variability within a population and the eventual repeatability across time and space may provide stability in a population facing environmental changes, by affecting individuals differently. Thus, the variability and repeatability of behaviours, habitats used, niches and migratory pathways could play an important role. Trindade petrels (Pterodroma arminjoniana) are threatened seabirds that breed year round on Trindade Island in the South Atlantic Ocean, migrate to North Atlantic Ocean in the non-breeding periods, and use wide oceanic areas. This study investigated the timing, at-sea distribution, and trophic niche throughout the annual cycle of the austral fall/winter breeding group of Trindade petrel and examined consistency in distribution and trophic niche used by the Trindade petrel at the individual level, in different breeding seasons, using geolocator tracking and stable isotope analysis. Results demonstrated that petrels breed annually, maintaining their breeding schedules. Petrels share a common, vast oligotrophic oceanic area during both breeding and non-breeding periods inside the South Atlantic and North Atlantic Subtropical Gyres, respectively. Two migratory patterns were identified and used repeatedly by individuals. Although petrels overlapped at-sea distributions in consecutive breeding seasons, consistency in parameters tested was not found. Breeding in two schedules along the year, in addition to the use of different migratory pathways and flexibility in their isotopic niche can be an advantage for Trindade petrel population to cope with environmental changes. Causes and consequences of variable niche and pathways used, and the existence of consistency and variability among birds breeding later on the year remain poorly-known.

An ecological niche has been defined as an n‐dimensional hypervolume formed by conditions and resources that species need to survive, grow, and reproduce. In practice, such niche dimensions are measurable and describe how species share resources, which has been thought to be a crucial mechanism for coexistence and a major driver of broad biodiversity patterns. Here, we investigate resource partitioning and trophic interactions of three sympatric, phylogenetically related and morphologically similar species of thrushes (Turdus spp.). Based on one year of data collected in southern Brazil, we investigated niche partitioning using three approaches: diet and trophic niche assessed by fecal analysis, diet and niche estimated by stable isotopes in blood and mixing models, and bipartite network analysis derived from direct diet and mixing model outputs. Approaches revealed that the three sympatric thrushes are generalists that feed on similar diets, demonstrating high niche overlap. Fruits from C3 plants were one of the most important food items in their networks, with wide links connecting the three thrush species. Turdus amaurochalinus and T. albicollis had the greatest trophic and isotopic niche overlap, with 90% and 20% overlap, respectively. There was partitioning of key resources between these two species, with a shared preference for fig tree fruits—Ficus cestrifolia (T. amaurochalinus PSIRI% = 11.3 and T. albicollis = 11.5), which was not present in the diet of T. rufiventris. Results added a new approach to the network analysis based on values from the stable isotope mixing models, allowing comparisons between traditional dietary analysis and diet inferred by isotopic mixing models, which reflects food items effectively assimilated in consumer tissues. Both are visualized in bipartite networks and show food‐consumers link strengths. This approach could be useful to other studies using stable isotopes coupled to network analysis, particularly useful in sympatric species with similar niches. Niche dimensions are measurable and describe how species share resources, which has been thought to be a crucial mechanism for coexistence and a major driver of broad biodiversity patterns. Morphologically, similar species of thrushes (Turdus spp.) are generalist species, but distinct, despite overlapping feeding habits allow coexistente.

Organisms tend to exhibit phenotypes that can be shaped by climate, commonly demonstrating clinal variations along latitudinal gradients. In vertebrates, air temperature plays a major role in shaping body size in both ectothermic and endothermic animals. However, additional small-scale environmental factors can also act as selection pressures in the marine ecosystem (e.g. primary productivity), evidencing multi-scale processes acting on marine organisms. In this study, we tested Bergmann’s rule in a widely distributed seabird, the brown booby Sula leucogaster, in addition to evaluating the relationship of sea surface temperature and chlorophyll α with phenotypes. We used traits from a morphometric dataset (culmen, wing chord, and tarsus length) and body mass of 276 brown boobies distributed on six breeding sites along a latitudinal gradient in the South Atlantic Ocean (0–27°S). We found significant differentiation among colonies, but phenotypic similarities were observed between colonies located at the extremes of the latitudinal gradient. As the colony nearest to the Equator, Saint Peter and Saint Paul archipelago, had the largest and heaviest individuals, the model containing only air temperature explained < 5% of the allometric variation, providing no substantial support for Bergmann’s rule. However, when we added the interaction of chlorophyll α and sea surface temperature the deviance explained rose to over 80%. Primary productivity and sea surface temperature do not follow a latitudinal gradient in the ocean and, therefore, the role of small-scale oceanographic processes in shaping body size and the importance of considering additional environmental variables when testing Bergmann’s rule in marine organisms are evident

The diet of the Kelp Gull ( Larus dominicanus ) was investigated at the northern limit of its distribution along the South American Atlantic coast. We used two complementary methods, pellet analysis and stable isotope analysis (SIA), to describe and compare Kelp Gull feeding ecology in freshwater and marine environments. The assimilated diet over two different time scales was investigated via SIA of plasma and red blood cells, blood components with different turnover rates. Fish composed the bulk of the diet of Kelp Gulls in both marine (White Croaker Micropogonias furnieri and Banded Croaker Paralonchurus brasiliensis ) and limnetic areas (Armoured Catfish Loricariidae and La Plata Croaker Pachyurus bonariensis ), despite the importance of benthic prey from the intertidal zone in samples collected from the marine environment (Wedge Clam Donax hanleyanus and the Yellow Clam Mesodesma mactroides ). The fish consumed by the gulls were common discards from fisheries in both environments, and marine bivalves were found at a high density at the marine beach. Diet varied between the different time scales analysed. Conventional diet data generally agreed with stable isotope model estimates, emphasising the importance of using complementary approaches in dietary studies.

Stable isotope analysis is an approach that allows inferring feeding ecology and trophic structure of populations, especially for species that are difficult to observe in natural habitats, such as marine turtles. This study investigated the niche breadth of adult and juvenile green sea turtles ( Chelonia mydas ) through δ 15 N and δ 13 C values in carapace scutes. During 2017 and 2018, tissues were collected from juveniles in a feeding area in southeastern Brazil ( n = 60) and from adults in a nesting area in northeastern Brazil, at Fernando de Noronha ( n = 21). Our results revealed no temporal variations in the isotopic values of adult green turtles and the mean δ 15 N values are compatible with the isotopic values of primarily herbivorous animals. In southeastern Brazil, the δ 13 C values and isotopic niche breadth differences observed in juvenile green turtles suggest that variations in habitat (i.e., channel between the municipalities of Ilhabela and São Sebastião - “SSC” and region comprising the other two municipalities of Ubatuba and Caraguatatuba - “CAU”, as defined in this study based on oceanographic current dynamics) can influence their isotopic niche. The isotopic values observed in juvenile green turtles demonstrated a high degree of feeding behavior plasticity and individual variability, which were possibly influenced by the dynamic of oceanographic currents and seasonal nutrient inputs. These findings help to elucidate the feeding behavior of green turtles at different life stages and the potential influence of oceanographic current dynamics in key feeding sites for juvenile green turtles.

Considerable progress in our understanding of long-distance migration has been achieved thanks to the use of small geolocator devices (GLS). The tracking of resident or short-distance migrant animals remains however challenging because geolocation errors are substantial and difficult to estimate. This study aims to examine the sex-specific marine space uses of a resident tropical seabird, the masked booby (Sula dactylatra), during its full annual life cycle at the Fernando de Noronha archipelago (Brazil). Masked boobies (n = 31) tagged with GLS recording light intensity, seawater immersion, and water temperature showed a resident behaviour over their entire annual cycle. A wavelet analysis of GLS data revealed oscillatory patterns of inferred longitude correlated with changes in immersion frequency. This synchronicity demonstrated that birds traveled away and back from the colony on consecutive trips of short length (∼ 2–4 days) and short range (∼ 100–300 km) eastward of the colony. Duration and range of trips depended on the sex of the individual and on the time of the year. Trip duration increased gradually from the end of the breeding period to the post-breeding period, probably due to the release of the central-place breeding constraints. During the pre-breeding period, females had farther ranges eastward and spent more time in water than males. Despite inherent limits of light-based geolocation, this study demonstrates the relevance of synchronicity analysis of GLS data for investigating year-round movements of resident or short-distance migrants.

Urbanization is a major form of landscape transformation that often results in habitat degradation and loss for birds. However, effects on avian populations are trait- and context-dependent, and persistence at urban patches is likely to be a function of habitat availability at the landscape scale. Here, we aimed to assess the breeding performance and foraging ecology of a widespread shorebird, the American Oystercatcher Haematopus palliatus , during the 2017–2018 and 2018–2019 breeding seasons at a small urban beach surrounded by a heterogeneous landscape in southern Brazil. Twelve pairs were able to breed consistently and successfully fledge offspring in 20% of nesting attempts at the urban site, with overall productivity of 0.37 fledglings per pair. Food remains collected within seven successful nesting territories and stable isotope analysis in blood samples of adults and chicks indicated that oystercatchers relied on invertebrates from both sandy beaches and rocky shores as food resources. Furthermore, eight out of 21 color-marked individuals from the urban beach were consistently recorded using an insular marine protected area ~ 2 km offshore, revealing a connection between unprotected and protected habitat patches. Although oystercatchers had to perform multiple foraging trips in order to collect food, the ability to explore different environments in the landscape may be critical in the region, especially with human disturbance at its peak on beaches during the summer. Our findings suggest that shorebirds breeding in urban areas may rely on heterogeneous landscapes, where distinct and protected habitat patches can provide complementary resources that allow breeding successfully.

Limited work to date has examined plastic ingestion in highly migratory seabirds like Great Shearwaters ( Ardenna gravis ) across their entire migratory range. We examined 217 Great Shearwaters obtained from 2008–2019 at multiple locations spanning their yearly migration cycle across the Northwest and South Atlantic to assess accumulation of ingested plastic as well as trends over time and between locations. A total of 2328 plastic fragments were documented in the ventriculus portion of the gastrointestinal tract, with an average of 9 plastic fragments per bird. The mass, count, and frequency of plastic occurrence (FO) varied by location, with higher plastic burdens but lower FO in South Atlantic adults and chicks from the breeding colonies. No fragments of the same size or morphology were found in the primary forage fish prey, the Sand Lance ( Ammodytes spp., n = 202) that supports Great Shearwaters in Massachusetts Bay, United States, suggesting the birds directly ingest the bulk of their plastic loads rather than accumulating via trophic transfer. Fourier-transform infrared spectroscopy indicated that low- and high-density polyethylene were the most common polymers ingested, within all years and locations. Individuals from the South Atlantic contained a higher proportion of larger plastic items and fragments compared to analogous life stages in the NW Atlantic, possibly due to increased use of remote, pelagic areas subject to reduced inputs of smaller, more diverse, and potentially less buoyant plastics found adjacent to coastal margins. Different signatures of polymer type, size, and category between similar life stages at different locations suggests rapid turnover of ingested plastics commensurate with migratory stage and location, though more empirical evidence is needed to ground-truth this hypothesis. This work is the first to comprehensively measure the accumulation of ingested plastics by Great Shearwaters over the last decade and across multiple locations spanning their yearly trans-equatorial migration cycle and underscores their utility as sentinels of plastic pollution in Atlantic ecosystems.

The marine habitat use of olive ridley sea turtles ( Lepidochelys olivacea ) from northeastern Brazil was analyzed via stable isotope analysis (SIA). Blood (red blood cells and serum), epidermis and scute samples from 46 nesting females were collected for SIA of carbon ( δ 13 C) and nitrogen ( δ 15 N) to infer the habitats used at distinct time windows. Such approach is possible because each tissue reflects consumer’s diet at different time scales due to different tissue turnover time. Prey representative of both neritic and oceanic realms was used as endpoints. Differences in the residence time of δ 13 C and δ 15 N among samples indicated a shift from oceanic feeding grounds to neritic habitats before nesting or effects of prolonged fasting on stable isotope values. However, two individuals seemed to have used neritic feeding habitats for longer timespans before the nesting period. Stable isotope mixing models demonstrated high individual variability, suggesting the variable use of non-breeding grounds. Moreover, serum indicated that olive ridleys might feed during the nesting season, most likely opportunistically on discards from trawl fisheries. Finally, through correlations of stable isotope values among tissues, this study provides equations for the conversion and adequate comparison between values from different tissues. Therefore, the habitats used by olive ridley sea turtles from Brazil are vast, encompassing both oceanic and neritic habitats, where they encounter pelagic longline and trawl fisheries, respectively. The high individual variability in the population results in turtles experiencing distinct and variable threats during their annual cycle.

Investigations of the genetic structure of populations over the entire range of a species yield valuable information about connectivity among populations. Seabirds are an intriguing taxon in this regard because they move extensively when not breeding, facilitating intermixing of populations, but breed consistently on the same isolated islands, restricting gene flow among populations. The degree of genetic structuring of populations varies extensively among seabird species but they have been understudied in their tropical ranges. Here, we address this across a broad spatial scale by using microsatellite and mitochondrial data to explore the population connectivity of 13 breeding populations representing the six subspecies of the white‐tailed tropicbird (Phaethon lepturus) in the Atlantic, Indian, and Pacific Oceans. Our primary aim was to identify appropriate conservation units for this little known species. Three morphometric characters were also examined in the subspecies. We found a clear pattern of population structuring with four genetic groups. The most ancient and the most isolated group was in the northwestern Atlantic Ocean. The South Atlantic populations and South Mozambique Channel population on Europa were genetically isolated and may have had a common ancestor. Birds from the Indo‐Pacific region showed unclear and weak genetic differentiation. This structuring was most well defined from nuclear and mtDNA markers but was less well resolved by morphological data. The validity of classifying white‐tailed tropicbirds into six distinct subspecies is discussed in light of our new findings. From a conservation standpoint our results highlight that the three most threatened conservation units for this species are the two subspecies of the tropical North and South Atlantic Oceans and that of Europa Island in the Indian Ocean.