Boldness predicts foraging behaviour, habitat use and chick growth in a central place marine predator.

Animal personality can shape individual's fitness. Yet, the mechanistic relationship by which individual's personality traits lead to variations in fitness remains largely underexplored. Here, we used novel object tests to measure boldness of chick-provisioning Cory's shearwaters (Calonectris borealis) from a coastal colony off west Portugal, and deployed GPS loggers to study their at-sea behaviour and distribution. We then tested whether boldness predicts individual differences in adult's trophic ecology and variations in chick growth, to assess potential implications of personality-specific foraging behaviours. Foraging effort was higher for shyer than for bolder individuals, which, during short forays, exhibited larger foraging ranges, and foraged in regions of higher and more variable bathymetry. This suggests that nearby the colony bolder individuals expanded their foraging area to maximize resource acquisition and increase the probability of foraging success. When endeavouring to longer distances, bolder individuals exhibited comparably shorter foraging ranges and targeted low bathymetry regions, likely with enhanced prey availability, while shyer individuals exhibited much larger foraging ranges indicating greater flexibility when foraging in oceanic realms. Despite such differences between bolder and shyer individuals their isotopic niches were similar. Yet, chicks raised by bolder parents grew at a faster rate than those raised by shyer parents. Together, our results suggest that differences in resource acquisition strategies could play a key role through which individual's boldness may influence breeding performance, even when individuals have similar isotopic preferences.

Omega-3 enriched chick diet reduces the foraging areas of breeders in two closely related shearwaters from contrasting marine environments.

Seabirds have evolved several life-history characteristics to help buffer environmental stochasticity. However, particularly during the breeding season, seabirds may be affected by reductions in prey availability and localised oceanographic conditions caused by variations in the environment. The increase in sea surface temperature, triggered by accelerated global warming, is impairing phytoplankton production of omega-3 fatty acids (FAs). Here, we assessed the ecological role of omega-3 FAs on chick development and subsequently on breeder foraging behaviour in two closely related shearwater species foraging in contrasting marine environments. We supplemented chicks with omega-3 FA pills or with control placebo pills and monitored chick growth, chick health status and breeder at-sea foraging behaviour using global positioning system devices. We found that omega-3 chick supplementation reduced the 95% kernel utilization distribution of short trips of Cape Verde shearwaters, but overall, breeders kept a similar foraging pattern between treatments, potentially influenced by predictable prey patches off the West African coast. In contrast, for Cory's shearwaters, the parents of the omega-3 group greatly reduced the foraging effort. This suggests that the proximity to productive prey patches around the colony may help birds to adjust their effort and, therefore, energy expenditure, to changes in the development of their offspring, as driven by their nutritional status. Overall, our results suggest a link between a chick diet enriched in omega-3 FAs and parental foraging effort, providing insight into their ability to cope with a changing and increasingly stochastic marine environment.

Foraging costs drive within-colony spatial segregation in shearwaters from two contrasting environments in the North Atlantic Ocean.

Foraging spatial segregation is frequent in central-place foragers during the breeding season, but very few studies have investigated foraging spatial segregation between adjacent sub-colonies. Here, we assessed for within-colony differences in the at-sea distribution, habitat use, trophic ecology and chick growth data of two Calonectris colonies differing in size, and breeding in two different environments in the North Atlantic Ocean. For this, we GPS tracked 52 Cory's shearwaters (Calonectris borealis) breeding in 2 small sub-colonies at Berlenga Island (Portugal) and 59 Cape Verde shearwaters (Calonectris edwardsii) breeding in 2 sub-colonies differing greatly in size at Raso Islet (Cabo Verde), over 2 consecutive breeding seasons (2017-2018), during chick-rearing. Cory's shearwaters from the two sub-colonies at Berlenga Island broadly overlapped in repeatedly used foraging patches close to the colony. In contrast, the foraging distribution of Cape Verde shearwaters was partially segregated in the colony surroundings, but overlapped at distant foraging areas off the west coast of Africa. Despite spatial segregation close to the colony, Cape Verde shearwaters from both sub-colonies departed in similar directions, foraged in similar habitats and exhibited mostly short trips within the archipelago of Cabo Verde. These results, corroborated with similar trophic ecology and chick growth rates between sub-colonies, support the idea that foraging spatial segregation in the colony surroundings was not likely driven by interference competition or directional bias. We suggest that high-quality prey patches are able to shape travel costs and foraging distribution of central-place foragers from neighbouring sub-colonies.

Oceans of stimuli: an individual-based model to assess the role of olfactory cues and local enhancement in seabirds' foraging behaviour.

Oceans are extremely dynamic environments, which poses challenges for top-predators such as seabirds to find food resources. Yet, seabirds evolved sensorial abilities (olfactory senses) along with complex behaviours (social information transfer through local enhancement) to improve foraging efficiency. Using the Cory's shearwater (Calonectris borealis) as a model species, we developed an individual-based model to explore the complementary role of different searching mechanisms (olfactory foraging and local enhancement) for the optimal foraging behaviour of pelagic seabirds during 1-day foraging trips around breeding colonies. Model outputs were compared with observed patterns of Cory's shearwaters distribution during local foraging trips. Also, the foraging efficiency of virtual individuals was analysed considering hypothetical scenarios of foraging conditions and densities of foraging individuals around breeding colonies. The results support the use of a combination of searching strategies by Cory's shearwaters, which produced representative patterns of space use from tracked individuals, including spatial foraging segregation of neighbouring sub-colonies. Furthermore, while the mechanisms underpinning local enhancement played a key role in mitigating sub-optimal foraging conditions, the use of olfactory senses conferred great adaptive foraging advantages over a wide range of environmental conditions. Our results also indicate a synergistic effect between the two strategies, which suggests that a multimodal foraging strategy is useful to forage in extremely dynamic environments. The developed model provides a basis for further investigation regarding the role of foraging mechanisms in the population dynamics of colonial animals, including the adaptive foraging behaviour of marine top predators to dynamic environmental conditions.

High mercury levels in Antarctic toothfish Dissostichus mawsoni from the Southwest Pacific sector of the Southern Ocean.

Mercury is a bioaccumulating toxic pollutant which can reach humans through the consumption of contaminated food (e.g. marine fish). Although the Southern Ocean is often portrayed as a pristine ecosystem, its fishery products are not immune to mercury contamination. We analysed mercury concentration (organic and inorganic forms - T-Hg) in the muscle of Antarctic toothfish, Dissostichus mawsoni, a long-lived top predator which supports a highly profitable fishery. Our samples were collected in three fishing areas (one seamount and two on the continental slope) in the Southwest Pacific Sector of the Southern Ocean during the 2016/2017 fishing season. Mercury levels and the size range of fish varied between fishing areas, with the highest levels (0.68 ± 0.45 mg kg-1 wwt) occurring on the Amundsen Sea seamount where catches were dominated by larger, older fish. The most parsimonious model of mercury concentration included both age and habitat (seamount vs continental slope) as explanatory variables. Mean mercury levels for each fishing area were higher than those in all previous studies of D. mawsoni, with mean values for the Amundsen Sea seamount exceeding the 0.5 mg kg-1 food safety threshold for the first time. It might therefore be appropriate to add D. mawsoni to the list of taxa, such as swordfish and sharks, which are known to exceed this threshold. This apparent increase in mercury levels suggests a recent contamination event which affected the Southwest Pacific sector, including both the Amundsen and Dumont D'Urville seas.

Long-term dietary shift and population decline of a pelagic seabird-A health check on the tropical Atlantic?

In the face of accelerating ecological change to the world's oceans, seabirds are some of the best bio-indicators of marine ecosystem function. However, unravelling ecological changes that pre-date modern monitoring programmes remains challenging. Using stable isotope analysis of feathers and regurgitants collected from sooty terns (Onychoprion fuscatus) nesting at a major Atlantic colony, we reconstructed a long-term dietary time series from 1890 to the present day and show that a significant dietary shift occurred during the second half of the twentieth century coinciding with an apparent population collapse of approximately 84%. After correcting for the "Suess Effect," δ13 C in feathers declined by ~1.5‰ and δ15 N by ~2‰ between the 1890s and the present day, indicating that birds changed their diets markedly over the period of population decline. Isotopic niches were equally wide before and after the population collapse but isotopic mixing models suggest that birds have grown ever more reliant on nutrient-poor squid and invertebrates as teleost fish have declined in availability. Given that sooty terns rely heavily on associations with sub-surface predators such as tuna to catch fish prey, the rapid expansion of industrialized fisheries for these species over the same period seems a plausible mechanism. Our results suggest that changes to marine ecosystems over the past 60 years have had a dramatic impact on the ecology of the most abundant seabird of tropical oceans, and highlight the potentially pervasive consequences of large predatory fish depletion on marine ecosystem function.

Characterization of MHC class I in a long distance migratory wader, the Icelandic black-tailed godwit.

The major histocompatibility complex (MHC) encodes proteins that are central for antigen presentation and pathogen elimination. MHC class I (MHC-I) genes have attracted a great deal of interest among researchers in ecology and evolution and have been partly characterized in a wide range of bird species. So far, the main focus has been on species within the bird orders Galliformes and Passeriformes, while Charadriiformes remain vastly underrepresented with only two species studied to date. These two Charadriiformes species exhibit striking differences in MHC-I characteristics and MHC-I diversity. We therefore set out to study a third species within Charadriiformes, the Icelandic subspecies of black-tailed godwits (Limosa limosa islandica). This subspecies is normally confined to parasite-poor environments, and we hence expected low MHC diversity. MHC-I was partially characterized first using Sanger sequencing and then using high-throughput sequencing (MiSeq) in 84 individuals. We verified 47 nucleotide alleles in open reading frame with classical MHC-I characteristics, and each individual godwit had two to seven putatively classical MHC alleles. However, in contrast to previous MHC-I data within Charadriiformes, we did not find any evidence of alleles with low sequence diversity, believed to represent non-classical MHC genes. The diversity and divergence of the godwits MHC-I genes to a large extent fell between the previous estimates within Charadriiformes. However, the MHC genes of the migratory godwits had few sites subject to positive selection, and one possible explanation could be a low exposure to pathogens.

Metabolic plasticity for subcutaneous fat accumulation in a long-distance migratory bird traced by 2H2O.

The migrant black-tailed godwit (Limosa limosa) traditionally used natural wetlands in the Iberian Peninsula to prepare for migratory flights by feeding mainly in estuaries. In recent decades, this species has become increasingly dependent on rice fields, thereby relying on a plant-based diet for fuelling. Dietary fatty acids (FA) seem to be determinant to the composition of accumulated subcutaneous fat in migratory birds. It is still unclear whether metabolic plasticity allows for modification and/or synthesis of FA, contributing to a lipid profile that enables a successful migratory performance. Deuterated water was administered to captive black-tailed godwits submitted to two diets (fly larvae versus rice) and the incorporation of deuterium (2H) into subcutaneous triglycerides was analyzed by NMR. A recently developed localized biopsy method for sampling subcutaneous fat was employed with later successful release of all birds into the wild. The average chemical structure reflected mostly a mixture of saturated and monounsaturated 16- and 18-carbon FA, a profile frequently found in migrant birds. Significantly higher levels of polyunsaturated FA, as well as detectable levels of n-3 FA, were observed in fly-larvae-fed birds. Excess 2H-enrichments in FA revealed significantly higher rates of fractional de novo lipogenesis and FA desaturation capacity in rice-fed birds. This novel and non-lethal tracer method revealed the capacity of this species to alter its lipid metabolism to compensate for a poorer dietary lipid contribution. Because of its versatility, adapting this method to other scenarios and/or other migratory species is considered feasible and cost-effective.

Characterization Through Multilocus Sequence Analysis of Borrelia turdi Isolates from Portugal.

Borrelia turdi is a spirochete from the Borrelia burgdorferi complex, first reported in Japan, that has been increasingly detected in Europe. This genospecies is mostly associated with avian hosts and their ornithophilic ticks such as Ixodes frontalis. In this study, we isolated B. turdi from five I. frontalis feeding on Turdus merula, Turdus philomelos, Parus major and Troglodytes troglodytes, and one Ixodes ricinus feeding on a T. merula in Portugal. These isolates were genetically characterised according to their 5S-23S rRNA intergenic spacer, 16S rRNA and through typing of seven housekeeping genes (multilocus sequence typing). Multilocus sequence analyses revealed that the strains isolated in our study, although belonging to B. turdi genospecies, are not identical to the B. turdi reference strain Ya501. Instead, our strains are separated into a clear defined group, suggesting that the European samples diverged genetically from the strain originally detected in Japan. Population analysis of 5S-23S rRNA sequences can further resolve subpopulations within B. turdi, but more samples from a large geographical scale and host range would be needed to assess potential phylogeographical patterns within this genospecies.

Pelagic seabird flight patterns are consistent with a reliance on olfactory maps for oceanic navigation.

Homing studies have provided tantalizing evidence that the remarkable ability of shearwaters (Procellariiformes) to pinpoint their breeding colony after crossing vast expanses of featureless open ocean can be attributed to their assembling cognitive maps of wind-borne odours but crucially, it has not been tested whether olfactory cues are actually used as a system for navigation. Obtaining statistically important samples of wild birds for use in experimental approaches is, however, impossible because of invasive sensory manipulation. Using an innovative non-invasive approach, we provide strong evidence that shearwaters rely on olfactory cues for oceanic navigation. We tested for compliance with olfactory-cued navigation in the flight patterns of 210 shearwaters of three species (Cory's shearwaters, Calonectris borealis, North Atlantic Ocean, Scopoli's shearwaters, C. diomedea Mediterranean Sea, and Cape Verde shearwaters, C. edwardsii, Central Atlantic Ocean) tagged with high-resolution GPS loggers during both incubation and chick rearing.We found that most (69%) birds displayed exponentially truncated scale-free(Lévy-flight like) displacements, which we show are consistent with olfactory-cued navigation in the presence of atmospheric turbulence. Our analysis provides the strongest evidence yet for cognitive odour map navigation in wild birds. Thus, we may reconcile two highly disputed questions in movement ecology, by mechanistically connecting Lévy displacements and olfactory navigation. Our approach can be applied to any species which can be tracked at sufficient spatial resolution, using a GPS logger.

Analysis of stable isotope ratios in blood of tracked wandering albatrosses fails to distinguish a δ(13) C gradient within their winter foraging areas in the southwest Atlantic Ocean.

RATIONALE: The main limitation of isotopic tracking for inferring distribution is the lack of detailed reference maps of the isotopic landscape (i.e. isoscapes) in the marine environment. Here, we attempt to map the marine δ(13) C isoscape for the southwestern sector of the Atlantic Ocean, and assess any temporal variation using the wandering albatross as a model species. METHODS: Tracking data and blood and diet samples were collected monthly from wandering albatrosses rearing chicks at Bird Island, South Georgia, during the austral winter between May and October 2009. The δ(13) C and δ(15) N values were measured by mass spectrometry in plasma and blood cells, and related to highly accurate data on individual movements and feeding activity obtained using three types of device: GPS, activity (immersion) loggers and stomach temperature probes. RESULTS: The tracked birds foraged in waters to the north or northwest of South Georgia, including the Patagonian shelf-break, as far as 2000 km from the colony. The foraging region encompassed the two main fronts in the Southern Ocean (Polar and Subantarctic fronts). The δ(13) C values varied by only 2.1 ‰ in plasma and 2.5 ‰ in blood cells, and no relationships were found between the δ(13) C values in plasma and the mean latitude or longitude of landings or feeding events of each individual. CONCLUSIONS: The failure to distinguish a major biogeographic gradient in δ(13) C values suggest that these values in the south Atlantic Ocean are fairly homogeneous. There was no substantial variation among months in either the δ(13) C or the δ(15) N values of plasma or blood cells of tracked birds. As birds did not show a significant change in diet composition or foraging areas during the study period, these results provide no evidence for major temporal variation in stable isotope ratios in consumer tissues, or in the regional marine isoscape in the austral winter of 2009.

Spatial foraging segregation by close neighbours in a wide-ranging seabird.

Breeding seabirds are central-place foragers and therefore exploit food resources most intensively nearer their colonies. When nesting aggregations are close to one another density-dependent competition is likely to be high, potentially promoting foraging segregation (i.e. neighbouring colonies may segregate to search for food in different areas). However, little is known about spatial segregation in foraging behaviour between closely adjacent colonies, particularly in species that are wide-ranging foragers. Here, we tested for foraging segregation between two sub-colonies of a wide-ranging seabird, Cory's shearwater Calonectris borealis, separated by only 2 km, on a small Island in the North Atlantic. During the 2010 chick-rearing period, 43 breeding adults of both sexes were simultaneously sampled at both sub-colonies. A GPS logger was deployed on each individual and removed after several foraging trips at sea. Blood samples (plasma and red blood cells) were collected from each tracked individual for stable isotope analysis. Results indicated partial spatial segregation between the two sub-colonies during local foraging trips (i.e. those of ≤1 day duration and 216 km from the colony) accounting for 84.2% of all trips recorded. The location of the breeding sub-colony influenced the direction of travel of birds during local trips resulting in sub-colony-specific foraging areas. Although the oceanographic conditions associated with the foraging range of the two sub-colonies differed, no differences were found in the habitat exploited and in their estimated diets. This suggests that birds concentrated their feeding activity in patches of similar habitat and prey during the chick-rearing period.

An holistic ecological analysis of the diet of Cory's shearwaters using prey morphological characters and DNA barcoding.

Knowledge of the dietary choices and trophic niches of organisms is the key to understanding their roles in ecosystems. In seabird diet studies, prey identification is a difficult challenge, often yielding results with technique-specific biases. Additionally, sampling efforts are often not extensive enough to reveal intrapopulational variation. Immature animals, which may constitute up to 50% of a population, may occupy a significantly different trophic niche to more experienced birds, but this remains largely unexplored. We investigated the diet of Cory's shearwater (Calonectris diomedea) from Selvagem Grande, an island located off the northwest African coast, collecting a total of 698 regurgitate samples over three consecutive breeding seasons. The diet was assessed using two complementary approaches for prey identification: conventional morphological analysis (using fish vertebrae, otoliths and cephalopod beaks) and DNA barcoding of the 16S rRNA mitochondrial gene, in cases where a positive identification could not be retrieved. Species assignments employed BLAST and distance-based methods, as well as direct optimization of the tree length based on unaligned sequences in POY. This method resulted in robust tree estimates and species assignments, showing its potential for DNA barcoding of stomach contents using hypervariable markers such as the 16S. The molecular approach increased taxonomic resolution and revealed an additional 17 taxa. Diet differed significantly according to breeding status, sex, breeding phase (prelaying and chick rearing) and year. Such direct evidence of trophic segregation within the same population has rarely been shown in seabirds and highlights the importance of including such variables in ecosystem-based management approaches.

Dynamics and effects of plastic contaminants' assimilation in gulls.

Polybrominated diphenyl ethers are persistent disrupters assimilated by organisms, yet little is known about their link to plastic ingestion and health effects. In an experiment, two groups of yellow-legged/lesser black-backed gulls (Larus michahellis/Larus fuscus) were fed plastics with BDE99 to assess leaching into brain, preen oil, liver and fat tissues and evaluate effects on health and stress parameters. Although most plastic was regurgitated, we observed a clear relation between plastic ingestion and chemical leaching. BDE99 exhibited higher levels in brain tissue of gulls from the plastic groups. Also, only values of cholinesterases measured in plasma were significantly reduced in the 'plastic' groups. Cholinesterase activity in the brain also tended to decrease, suggesting a negative effect in gulls' neurofunction. Results indicate that chemical leaching occurs, even when plastics stay in the stomach for a short period of time and showed that this can affect gulls' health.

Effect of exotic mammalian predators on parasites of Cory's shearwater: ecological effect on population health and breeding success.

Predator activity around the nests induces stress in breeding birds, which may have weaker immunity and are therefore more susceptible to parasite infections. The influence of predators on parasites has only been observed in land birds, and most studies are experimental. As seabird colonies offer excellent conditions for parasites, here we assess the influence of mouse, rat, and cat activity on parasites in Cory's shearwater (Calonectris diomedea borealis). Adults were examined for blood parasites and one adult and the juvenile from 53 nests were inspected for ectoparasites over two consecutive years (2010 and 2011). Nests differed in their physical characteristics and indices of mammal predator activity and were checked weekly to assess breeding success. Our results showed absence of blood parasites. Among the environmental factors, predator pressure received the most support (89 %) from the data as influencing nest ectoparasite intensity. Birds most infected had worse body condition, and breeding success was negatively influenced by predator activity and ectoparasite intensity. To our knowledge, this is the first analysis of the interaction between mammal predators and ectoparasites in seabird species and supports greater protection through eradication efforts. In addition, we provide the first data on the endoparasite fauna of Cory's shearwater.

Hidden haemosporidian infections in Ruffs (Philomachus pugnax) staging in Northwest Europe en route from Africa to Arctic Europe.

In their African freshwater wintering habitats, shorebirds show a high prevalence of blood parasites, whereas no parasites are detected elsewhere along the migration route. We looked at two genera of haemosporidian parasites, Haemoproteus and Plasmodium, in the long-distance migrating Ruff (Philomachus pugnax) along a geographical/seasonal gradient to verify the infection pattern and examine possible hidden organ infections at European staging areas. We amplified parasite DNA from blood of 53 healthy birds wintering in Mali, 53 samples of seven organ tissues (spleen, liver, kidneys, heart, lungs, brain, and pectoral muscle) from healthy individuals caught during spring migration, and 18 weak birds found sick in summer in The Netherlands. We confirm that Ruffs wintering in Africa carried blood infections and that some infections developed into hidden organ infections during spring migration. Moreover, sick birds either had new infections (in one juvenile) or relapses (in an adult harboring an African lineage). Our results suggest that some parasites develop latency. This strategy may be beneficial for the parasite as it may take control over reappearance in the blood to help further transmission.

A century of mercury: Ecosystem-wide changes drive increasing contamination of a tropical seabird species in the South Atlantic Ocean.

Mercury (Hg) is a highly toxic metal that adversely impacts human and wildlife health. The amount of Hg released globally in the environment has increased steadily since the Industrial Revolution, resulting in growing contamination in biota. Seabirds have been extensively studied to monitor Hg contamination in the world's oceans. Multidecadal increases in seabird Hg contamination have been documented in polar, temperate and subtropical regions, whereas in tropical regions they are largely unknown. Since seabirds accumulate Hg mainly from their diet, their trophic ecology is fundamental in understanding their Hg exposure over time. Here, we used the sooty tern (Onychoprion fuscatus), the most abundant tropical seabird, as bioindicator of temporal variations in Hg transfer to marine predators in tropical ecosystems, in response to trophic changes and other potential drivers. Body feathers were sampled from 220 sooty terns, from museum specimens (n = 134) and free-living birds (n = 86) from Ascension Island, in the South Atlantic Ocean, over 145 years (1876-2021). Chemical analyses included (i) total- and methyl-Hg, and (ii) carbon (δ1³C) and nitrogen (δ15N) stable isotopes, as proxies of foraging habitat and trophic position, respectively, to investigate the relationship between trophic ecology and Hg contamination over time. Despite current regulations on its global emissions, mean Hg concentrations were 58.9% higher in the 2020s (2.0 µg g-1, n = 34) than in the 1920s (1.2 µg g-1, n = 107). Feather Hg concentrations were negatively and positively associated with δ1³C and δ15N values, respectively. The sharp decline of 2.9 ‰ in δ1³C values over time indicates ecosystem-wide changes (shifting primary productivity) in the tropical South Atlantic Ocean and can help explain the observed increase in terns' feather Hg concentrations. Overall, this study provides invaluable information on how ecosystem-wide changes can increase Hg contamination of tropical marine predators and reinforces the need for long-term regulations of harmful contaminants at the global scale.

DNA metabarcoding to assess prey overlap between tuna and seabirds in the Eastern tropical Atlantic: Implications for an ecosystem-based management.

Overfishing has been drastically changing food webs in marine ecosystems, and it is pivotal to quantify these changes at the ecosystem level. This is especially important for ecosystems with a high diversity of top predators such as the Eastern Atlantic marine region. In this work we used high-throughput sequencing methods to describe the diet of the two most abundant tuna species, the Skipjack tuna (Katsuwonus pelamis) and the Yellowfin tuna (Thunnus albacares), highly targeted by fisheries off west Africa. We also explored prey diversity overlap between these tuna species and the seabird species breeding in Cabo Verde that are most likely to share prey preferences and suffer from bycatch, the Brown booby (Sula leucogaster) and Cape Verde shearwater (Calonectris edwardsii). Overall, the diet of both tuna species was more diverse than that of seabirds. Skipjack tuna diet was dominated by prey from lower trophic levels, such as krill, anchovies, and siphonophores, while the Yellowfin tuna diet was mainly based on epipelagic fish such as flying and halfbeak fishes. Some of the most abundant prey families detected in the Yellowfin tuna diet were shared with both seabird species, resulting in a high prey diversity overlap between this tuna species and seabirds These results have implications for the management of tuna fisheries in the Eastern Tropical Atlantic, because a large decrease of both tuna species might have cascading effects on both primary and secondary consumer levels, and the decrease of these underwater predators may have implications on the viability of tropical seabird populations.

Host-parasite associations and host-specificity in haemoparasites of reed bed passerines.

The host specificity and host sharing of avian haemoparasites (genera Haemoproteus and Plasmodium) is still poorly known, although they infect a large proportion of several studied bird populations. This study used molecular techniques to detect haemoparasites in marsh warblers and in other passerines that feed in reed beds, at 4 sites in Portugal. The host-specificity of the parasite lineages was analysed and compared with other cases described in the literature to assess whether apparent host specificity changes according to the studied system. Nine lineages of Haemoproteus and 15 of Plasmodium were found, of which only 10 Plasmodium were proven to have local transmission. Each lineage was confined to a distinct set of host species. The distribution of parasites in the host species was non-nested, meaning that specialist lineages did not always share hosts with generalists. The most prevalent lineages were those with a wider host range, indicating that the ability to infect more hosts will enhance a parasite's prevalence in its entire host range. We also found that in our areas, a specialist parasite (H. MW1) appears to have a more generalist character than described in the literature, suggesting that a parasite's apparent specialization can depend on the type of host species sampled.

Avian malaria infections in western European mosquitoes.

In the complex life cycle of avian malaria parasites (Plasmodium sp.), we still have a poor understanding on the vector-parasite relationships. This study described the community of potential avian malaria vectors in four Portuguese reedbeds. We tested if their geographical distribution differed, and investigated on their Plasmodium infections. The mosquitoes' feeding preferences were evaluated using CO(2), mice, and birds as baits. The most abundant species were Culex pipiens, Culex theileri, and Ochlerotatus caspius (and, in one site, Coquillettidia richiardii). Plasmodium lineages SGS1 and SYAT05 were found in unengorged Cx. pipiens and Cx. theileri, respectively, suggesting that these mosquitoes were competent vectors of those lineages. The species' abundance was significantly different among sites, which may help to explain the observed differences in the prevalence of SGS1. At the study sites, SGS1 was detected in the most abundant mosquito species and reached a high prevalence in the most abundant passerine species. Probably, this parasite needs abundant hosts in all phases of its cycle to keep a good reservoir of infection in all its stages. Cq. richiardii showed an opportunistic feeding behavior, while Cx. pipiens appeared to be more mammophilic than previously described, perhaps because the used avian bait was not its preferential target. In one of the study sites, mosquitoes seem to be attracted to the Spotless Starling Sturnus unicolor, an abundant bird species that may be an important local reservoir of avian malaria infections. To our knowledge, this is the first report of detection of avian Plasmodium DNA from European mosquitoes.