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.

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.

Microplastics ingestion and endocrine disrupting chemicals (EDCs) by breeding seabirds in the east tropical Atlantic: Associations with trophic and foraging proxies (δ15N and δ13C)

In this study we found that endocrine disrupting chemicals (EDCs) were omnipresent in a tropical seabird community comprising diverse ecological guilds and distinct foraging and trophic preferences. Because EDCs tend to bioaccumulate within the food web and microplastics can absorb and release harmful chemical compounds, our findings draw attention to the potential threats to wildlife. Thus, the goal of this study was to investigate the role of plastic ingestion, trophic and foraging patterns (δ15N and δ13C) of five tropical seabird species breeding in sympatry, on the exposure to EDCs, namely Polybrominated diphenyl ethers (PBDEs), methoxylated polybrominated diphenyl ethers (MeO-PBDEs) and personal care products (PCPs, e.g., musk fragrances and UV-filters). Results indicated that microplastics occurrence and EDCs detection frequency varied among species. Microplastics occurrence was higher in species with dual and coastal foraging strategies. Preen oil had higher levels of MeO-PBDEs and PCPs, while serum had higher levels of PBDEs. In brown boobies, the correlation between microplastics and ∑PBDEs levels was significant, suggesting that microplastics ingestion is a key PBDEs route. Trophic position (δ15N) plays a key role in PBDEs accumulation, particularly in Bulwer's petrel, which occupies a high trophic position and had more specialized feeding ecology than the other species. MeO-PBDEs were linked to foraging habitat (δ13C), although the link to foraging locations deserves further investigation. Overall, our findings not only fill key gaps in our understanding of seabirds' exposure to microplastics and EDCs, but also provide an essential baseline for future research and monitoring efforts. These findings have broader implications for the marine wildlife conservation and pollution management in sensitive environments, such as the tropical regions off West Africa.

Anthropogenic debris ingestion in a tropical seabird community: Insights from taxonomy and foraging distribution

Oceans have been considered as an unlimited supply of goods and services, but resource extraction and waste disposal became ubiquitous and have been damaging the health of marine ecosystems. Finding suitable sentinel species of the human impacts on the oceans is thus imperative, since they may work as early warnings of disruptive situations. In this study, we investigated how taxonomy and foraging distribution influenced the occurrence of anthropogenic debris among five seabird species inhabiting the tropical Atlantic region. Occurrence of anthropogenic debris was assessed using faeces of breeding individuals as a proxy of ingestion. A total of 268 particles were extracted from all samples. The categories "fragments" and "fibres", as well as the colour "blue", were the most prevalent characteristics across species. There was a high diversity of polymers from cellulosic particles to synthetic plastics (Anthropogenic Cellulosic 26.9 %; Polyester 7.7 %; Varnish 5.8 %; Polypropylene 1.9 %). Species with a more coastal foraging strategy exhibited higher occurrence and number of anthropogenic debris when compared to species foraging comparably more in pelagic areas. This suggests that anthropogenic debris are more prevalent in coastal foraging areas, where human activities occur in higher number and frequency (e.g., fisheries) and sources of freshwater input from inland are at close distance. These results provide more evidence to the growing perception on the ubiquity and diversity of anthropogenic debris in the marine environment, and further support the usefulness of using seabirds as bio-indicators of anthropogenic pollution in both neritic and oceanic regions.

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.

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.

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.

Fatty acids composition in yellow-legged (Larus michahellis) and lesser black-backed (Larus fuscus) gulls from natural and urban habitats in relation to the ingestion of anthropogenic materials

Urban habitats offer spatially and temporally predictable anthropogenic food sources for opportunistic species, such as several species of gulls that are known to exploit urban areas and take advantage of accessible and diverse food sources, reducing foraging time and energy expenditure. However, human-derived food may have a poorer nutritional quality than the typical natural food resources and foraging in urban habitats may increase birds' susceptibility of ingesting anthropogenic debris materials, with unknown physiological consequences for urban dwellers. Here we compare the fatty acids (FA) composition of two opportunistic gull species (the yellow-legged gull, Larus michahellis, and the lesser black-backed gull, Larus fuscus) from areas with different levels of urbanization, to assess differences in birds' diet quality among foraging habitats, and we investigate the effects of ingesting anthropogenic materials, a toxicological stressor, on gulls' FA composition. Using GC-MS, 23 FAs were identified in the adipose tissue of both gull species. Significant differences in gulls' FA composition were detected among the three urbanization levels, mainly due to physiologically important highly unsaturated FAs that had lower percentages in gulls from the most urbanized habitats, consistent with a diet based on anthropogenic food resources. The deficiency in omega (ω)-3 FAs and the higher ω-6:ω-3 FAs ratio in gulls from the most urbanized location may indicate a diet-induced susceptibility to inflammation. No significant differences in overall FA composition were detected between gull species. While we were unable to detect any effect of ingested anthropogenic materials on gulls' FA composition, these data constitute a valuable contribution to the limited FA literature in gulls. We encourage studies to explore the long-term physiological effects of the lower nutritional quality diet for urban dwellers, and to detect the sub-lethal impacts of the ingestion of anthropogenic materials.

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.

Year-round at-sea distribution and trophic resources partitioning between two sympatric Sulids in the tropical Atlantic

In the oligotrophic tropical marine environment resources are usually more patchily distributed and less abundant to top predators. Thus, spatial and trophic competition can emerge, especially between related seabird species belonging to the same ecological guild. Here we studied the foraging ecology of two sympatric species-brown booby (BRBO) Sula leucogaster (breeding) and red-footed boobies (RFBO) Sula sula (non-breeding)-at Raso islet (Cabo Verde), across different seasons. Sexual segregation was only observed during Jun-Oct, when RFBO were present, with larger females BRBO remaining closer to the colonies, while males and RFBO travelled further and exploited different habitats. Overall, species appeared to prefer areas with specific oceanic features, particularly those related with oceanic currents and responsible for enhancing primary productivity in tropical oceanic areas (e.g. Sea Surface Height and Ocean Mixed Layer Thickness). Female BRBOs showed high foraging-site fidelity during the period of sympatry, while exploiting the same prey species as the other birds. However, during the months of co-existence (Jun.-Oct.), isotopic mixing models suggested that female BRBO would consume a higher proportion of epipelagic fish, whereas female RFBO would consume more squid compared to the other birds, possibly due to habitat-specific prey availability and breeding energy-constraints for BRBO. We conclude that divergent parental roles, environmental conditions, habitat preference and competition could be mechanisms simultaneously underlying sexual segregation for BRBO during a period of co-existence, while inter-specific foraging differences appear to be more affected by habitat preference and different breeding stages. These results support previous statements that BRBO can adapt their foraging ecology to different circumstances of environmental conditions and competition, and that marine physical features play an important role in foraging decisions of boobies.

Ingestion of anthropogenic materials by yellow-legged gulls (Larus michahellis) in natural, urban, and landfill sites along Portugal in relation to diet composition

Pollution is a global concern, increasing rapidly throughout marine and terrestrial ecosystems, and affecting many species. Urbanization enhances waste production, leading to the opening of landfills that constitute a spatially and temporally predictable food source for opportunistic species. Several species of gulls are known to exploit and breed in urban areas, taking advantage of accessible and diverse food resources. The exploitation of anthropogenic food subsidies at sea (e.g. fishery discards), urban sites, and landfills leads to debris ingestion by gulls with potential negative effects. Here we characterize anthropogenic debris ingested by yellow-legged gulls (Larus michahellis) along Portugal, by analysing the content of pellets collected in (1) natural and urban breeding locations, and in (2) urban and landfill resting sites, to assess seasonal patterns in the ingestion of anthropogenic debris. We also relate diet with the presence of anthropogenic debris. Debris materials were found in 28.8% of pellets from breeding locations (natural and urban) and in 89.7% of pellets from resting sites (urban and landfill). Gulls from the most urbanized breeding location exhibited higher levels of ingested materials during the entire breeding cycle, however, gulls from a natural breeding site also ingested high levels of debris during the pre-breeding season. At resting sites, small seasonal differences were detected in the number and mass of debris items ingested, which were both higher during spring and summer. Gulls that typically fed on pelagic fish had significantly less sheet and fragment plastics in their pellets. The presence of certain debris categories in gull pellets was positively related to the presence of some prey items, suggesting that gulls may accidentally ingest debris while foraging at multiple habitats. The quantity of anthropogenic materials ingested by gulls from urban locations and landfills indicates a need for improved waste management.

Inter-annual changes in oceanic conditions drives spatial and trophic consistency of a tropical marine predator

Pelagic seabirds exhibit plasticity in foraging characteristics in relation to oceanographic conditions. This should be particularly relevant in tropical marine environments where food resources are naturally more unpredictable. We studied how inter-annual variations (2013-2018) in tropical oceanographic conditions (driver of oceanic productivity) can influence the spatial and trophic ecology of Cape Verde shearwater (Calonectris edwardsii) during the breeding season. During years of poor oceanographic conditions around the colony, birds engaged in longer trips to West Africa, showed higher spatial and behavioural consistency, and presented a wider isotopic niche. Opposite patterns were generally found for years of good oceanographic conditions, when birds foraged more on their colony surroundings. New foraging areas off West Africa were highlighted as relevant, especially during years of poor environmental conditions. This study highlights the need for long-term studies to assess variation in foraging areas and foraging decisions by seabird populations.

Characterization of anthropogenic materials on yellow-legged gull (Larus michahellis) nests breeding in natural and urban sites along the coast of Portugal

Anthropogenic materials are a persistent pressure on ecosystems, affecting many species. Seabirds can collect these materials to construct their nests, which may modify nest characteristics and cause entanglement of chicks and adults, with possible consequences on breeding success. The incorporation of anthropogenic materials in nests of seabird species that breed in both natural and urban environments, such as gulls, is poorly known. Here, we characterize and compare anthropogenic materials incorporated in yellow-legged gull (Larus michahellis) nests from two natural and two urban breeding sites across their Portuguese breeding range and during 2 consecutive years. Anthropogenic materials were found in 2.6% and 15.4% of gull nests from natural locations and in 47.6% and 95.7% of nests from urban breeding sites. No differences were found on hatching success between urban and natural breeding colonies. A significantly higher number of anthropogenic materials were found in the largest and more populated urban breeding colony, which on average included items of a greater mass but smaller size than items from the other three colonies. The higher incorporation of anthropogenic materials in urban locations could be a consequence of a lower access to natural nest construction materials and higher availability of anthropogenic debris. The quantity and diversity of anthropogenic materials incorporated in gull nests from urban locations indicate a need for improved debris management in urban settlements.

Spatial ecology of closely related taxa: the case of the little shearwater complex in the North Atlantic Ocean

Seabirds inhabiting vast water masses provide numerous examples where opposing phenomena, such as natal and breeding philopatry vs. vagility have dug cryptic taxonomic boundaries among closely related taxa. The taxonomy of little shearwaters of the North Atlantic Ocean (Little–Audubon’s shearwater complex, Puffinus assimilis–lherminieri) still remains unclear, and complementary information on non-breeding distributions and at-sea behaviour becomes essential to unravel divergent local adaptations to specific habitats. Using miniaturized light-level geolocators from seven study areas in the North Atlantic, we evaluate the spatial and habitat segregation, estimate the timing of their key life-cycle events and describe the at-sea behaviour of three taxa of these little shearwaters year-round to distinguish ecological patterns and specializations that could ultimately unravel potential lineage divergences. We also assess morphometric data from birds that were breeding at each study area to further discuss potential adaptations to specific habitats. Our results show that, while birds from different taxa segregated in space and habitats, they share ecological plasticity, similar annual phenology and diel foraging behaviour. These ecological inconsistencies, while defining the evolutionary stressors faced by these taxa, do not suggest the existence of three Evolutionary Significant Units. However, they confirm the recent evolutionary divergence among the three little shearwaters of the North Atlantic.

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.

Olfactory-cued navigation in shearwaters: linking movement patterns to mechanisms

After foraging in the open ocean pelagic birds can pinpoint their breeding colonies, located on remote islands in visually featureless seascapes. This remarkable ability to navigate over vast distances has been attributed to the birds being able to learn an olfactory map on the basis of wind-borne odors. Odor-cued navigation has been linked mechanistically to displacements with exponentially-truncated power-law distributions. Such distributions were previously identified in three species of Atlantic and Mediterranean shearwaters but crucially it has not been demonstrated that these distributions are wind-speed dependent, as expected if navigation was olfactory-cued. Here we show that the distributions are wind-speed dependent, in accordance with theoretical expectations. We thereby link movement patterns to underlying generative mechanisms. Our novel analysis is consistent with the results of more traditional, non-mathematical, invasive methods and thereby provides independent evidence for olfactory-cued navigation in wild birds. Our non-invasive diagnostic tool can be applied across taxa, potentially allowing for the assessment of its pervasiveness.

Environmentally driven sexual segregation in a marine top predator

Sexual segregation in foraging occurs in many animal species, resulting in the partitioning of resources and reduction of competition between males and females, yet the patterns and drivers of such segregation are still poorly understood. We studied the foraging movements (GPS-tracking), habitat use (habitat modelling) and trophic ecology (stable isotope analysis) of female and male Cory’s shearwaters Calonectris borealis during the mid chick-rearing period of six consecutive breeding seasons (2010–2015). We found a clear sexual segregation in foraging in years of greater environmental stochasticity, likely years of lower food availability. When food became scarce, females undertook much longer foraging trips, exploited more homogeneous water masses, had a larger isotopic niche, fed on lower trophic level prey and exhibited a lower body condition, when compared to males. Sexual competition for trophic resources may be stronger when environmental conditions are poor. A greater foraging success of one sex may result in differential body condition of pair mates when enduring parental effort, and ultimately, in an increased probability of breeding failure.

Breeding biology of a winter-breeding procellariiform in the North Atlantic, the Macaronesian shearwater Puffinus lherminieri baroli

The breeding success of burrow-nesting seabirds may be influenced by both nest site characteristics and oceanographic conditions influencing food availability at sea. In this study we describe the breeding biology of the winter-breeding Macaronesian shearwater (Puffinus lherminieri baroli), including nest site characteristics and interspecific competition. We also evaluate the possible effects of changing oceanographic conditions on breeding phenology and breeding success. The study was carried out over two breeding seasons on two islands in the North Atlantic Ocean, Cima Islet and Selvagem Grande. Oceanographic characteristics differed between years. On a regional scale, the North Atlantic Oscillation (NAO) index was low and negative in 2011, and on a local scale, birds used areas with significantly lower values of chlorophyll a concentration and significantly higher values of sea surface temperature anomalies. Hatching success was higher in 2012 than in 2011. At both colonies, egg cracking was the main cause of hatching failure, but in 2011 several eggs on Selvagem Grande were deserted. In 2012 birds laid earlier and chicks had longer wings and were heavier. At both colonies, nests that were deeper, were sheltered from prevailing winds and had small chambers and a soil substrate had a higher probability of being used successfully by the birds. Nests occupied solely by Macaronesian shearwaters were much deeper and had less volume than nests shared with other species. Our study suggests that the breeding success of Macaronesian shearwaters is strongly related to nest site characteristics and that at-sea environmental conditions exert a strong influence on reproductive parameters, with birds breeding in a poor year (evaluated in terms of lower marine productivity) laying much later and their chicks growing at a slower rate than in a good year. The influence of nest site characteristics and environmental conditions may be very important for understanding the breeding ecology of Procellariiformes and may help explain the negative population trend of Macaronesian shearwaters.

Lévy patterns in seabirds are multifaceted describing both spatial and temporal patterning

Background

The flight patterns of albatrosses and shearwaters have become a touchstone for much of Lévy flight research, spawning an extensive field of enquiry. There is now compelling evidence that the flight patterns of these seabirds would have been appreciated by Paul Lévy, the mathematician after whom Lévy flights are named. Here we show that Lévy patterns (here taken to mean spatial or temporal patterns characterized by distributions with power-law tails) are, in fact, multifaceted in shearwaters being evident in both spatial and temporal patterns of activity.

Results

We tested for Lévy patterns in the at-sea behaviours of two species of shearwater breeding in the North Atlantic Ocean (Calonectris borealis) and the Mediterranean sea (C. diomedea) during their incubating and chick-provisioning periods. We found that distributions of flight durations, on/in water durations and inter-dive time-intervals have power-law tails and so bear the hallmarks of Lévy patterns.

Conclusions

The occurrence of these statistical laws is remarkable given that bird behaviours are strongly shaped by an individual’s motivational state and by complex environmental interactions. Our observations could take Lévy patterns as models of animal behaviour to a new level by going beyond the characterisation of spatial movements to characterise how different behaviours are interwoven throughout daily animal life.

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.

Global spatial ecology of three closely-related gadfly petrels

The conservation status and taxonomy of the three gadfly petrels that breed in Macaronesia is still discussed partly due to the scarce information on their spatial ecology. Using geolocator and capture-mark-recapture data, we examined phenology, natal philopatry and breeding-site fidelity, year-round distribution, habitat usage and at-sea activity of the three closely-related gadfly petrels that breed in Macaronesia: Zino’s petrel Pterodroma madeira, Desertas petrel P. deserta and Cape Verde petrel P. feae. All P. feae remained around the breeding area during their non-breeding season, whereas P. madeira and P. deserta dispersed far from their colony, migrating either to the Cape Verde region, further south to equatorial waters in the central Atlantic, or to the Brazil Current. The three taxa displayed a clear allochrony in timing of breeding. Habitat modelling and at-sea activity patterns highlighted similar environmental preferences and foraging behaviours of the three taxa. Finally, no chick or adult was recaptured away from its natal site and survival estimates were relatively high at all study sites, indicating strong philopatry and breeding-site fidelity for the three taxa. The combination of high philopatry, marked breeding asynchrony and substantial spatio-temporal segregation of their year-round distribution suggest very limited gene flow among the three taxa.

Population-Scale Foraging Segregation in an Apex Predator of the North Atlantic

In this work we investigated the between-colony spatial, behavioural and trophic segregation of two sub-populations of the elusive Macaronesian shearwaters Puffinus baroli breeding only ~340 km apart in Cima Islet (Porto Santo Island) and Selvagem Grande Island. Global location sensing (gls) loggers were used in combination with the trophic ecology of tracked individuals, inferred from the isotopic signatures of wing feathers. Results suggest that these two Macaronesian shearwater sub-populations do segregate during the non-breeding period in some ‘sub-population-specific’ regions, by responding to different oceanographic characteristics (habitat modelling). Within these disparate areas, both sub-populations behave differently (at-sea activity) and prey on disparate trophic niches (stable isotope analysis). One hypothesis would be that each sub-population have evolved and adapted to feed on particular and ‘sub-population-specific’ resources, and the segregation observed at the three different levels (spatial, behavioural and trophic) might be in fact a result of such adaptation, from the emergence of ‘cultural foraging patterns’. Finally, when comparing to the results of former studies reporting on the spatial, behavioural and trophic choices of Macaronesian shearwater populations breeding on Azores and Canary Islands, we realized the high ecological plasticity of this species inhabiting and foraging over the North-East Atlantic Ocean.

Colony Foundation in an Oceanic Seabird

Seabirds are colonial vertebrates that despite their great potential for long-range dispersal and colonization are reluctant to establish in novel locations, often recruiting close to their natal colony. The foundation of colonies is therefore a rare event in most seabird species and little is known about the colonization process in this group. The Cory’s shearwater (Calonectris diomedea) is a pelagic seabird that has recently established three new colonies in Galicia (NE Atlantic) thus expanding its distribution range 500 km northwards. This study aimed to describe the establishment and early progress of the new Galician populations and to determine the genetic and morphometric characteristics of the individuals participating in these foundation events. Using 10 microsatellite loci, we tested the predictions supported by different seabird colonization models. Possibly three groups of non-breeders, adding up to around 200 birds, started visiting the Galician colonies in the mid 2000’s and some of them eventually laid eggs and reproduced, thus establishing new breeding colonies. The Galician populations showed a high genetic diversity and a frequency of private alleles similar to or even higher than some of the large historical populations. Most individuals were assigned to several Atlantic populations and a few (if any) to Mediterranean colonies. Our study suggests that a large and admixed population is settling in Galicia, in agreement with predictions from island metapopulation models of colonization. Multiple source colonies imply that some birds colonizing Galicia were dispersing from very distant colonies (> 1500 km). Long-distance colonizations undertaken by relatively large and admixed groups of colonizers can help to explain the low levels of genetic structure over vast areas that are characteristic of most oceanic seabird species.

Feathers as a Tool to Assess Mercury Contamination in Gentoo Penguins: Variations at the Individual Level

Feathers have been widely used to assess mercury contamination in birds as they reflect metal concentrations accumulated between successive moult periods: they are also easy to sample and have minimum impact on the study birds. Moult is considered the major pathway for mercury excretion in seabirds. Penguins are widely believed to undergo a complete, annual moult during which they do not feed. As penguins lose all their feathers, they are expected to have a low individual-variability in feather mercury concentration as all feathers are formed simultaneously from the same somatic reserves. This assumption is central to penguin studies that use feathers to examine the annual or among-individual variation in mercury concentrations in penguins. To test this assumption, we measured the mercury concentrations in 3-5 body feathers of 52 gentoo penguins (Pygoscelis papua) breeding at Bird Island, South Georgia (54°S 38°W). Twenty-five percent of the penguins studied showed substantial within-individual variation in the amount of mercury in their feathers (Coefficient of Variation: 34.7-96.7%). This variation may be caused by differences in moult patterns among individuals within the population leading to different interpretations in the overall population. Further investigation is now needed to fully understand individual variation in penguins' moult.

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.

The interaction between reproductive cost and individual quality is mediated by oceanic conditions in a long-lived bird

Environmental variability, costs of reproduction, and heterogeneity in individual quality are three important sources of the temporal and interindividual variations in vital rates of wild populations. Based on an 18-year monitoring of an endangered, recently described, long-lived seabird, Monteiro's Storm-Petrel (Oceanodroma monteiroi), we designed multistate survival models to separate the effects of the reproductive cost (breeders vs. nonbreeders) and individual quality (successful vs. unsuccessful breeders) in relation to temporally variable demographic and oceanographic properties. The analysis revealed a gradient of individual quality from nonbreeders, to unsuccessful breeders, to successful breeders. The survival rates of unsuccessful breeders (0.90 +/- 0.023, mean +/- SE) tended to decrease in years of high average breeding success and were more sensitive to oceanographic variation than those of both (high-quality) successful breeders (0.97 +/- 0.015) and (low-quality) nonbreeders (0.83 +/- 0.028). Overall, our results indicate that reproductive costs act on individuals of intermediate quality and are mediated by environmental harshness.

The influence of diet on mercury intake by little tern chicks

We assessed mercury levels in the feathers of little tern (Sternula albifrons) chicks from hatching to fledging and in their prey captured by adults in three main foraging habitats: lagoon, salinas, and adjacent sea. These data were used to model mercury concentration in chick feathers through food ingestion, in order to explore the effects that changes in diet would have on the mercury burden of chicks as they aged. The mercury concentration in feathers of chicks raised in sandy beaches was higher than in those raised in salinas. Lagoon prey had a significantly higher mercury concentration (0.18 +/- 0.09 microg g(-1) dry weight [d.w.]) than prey from salinas and the adjacent sea (both 0.06 +/- 0.03 microg g(-1) d.w.). In relation to prey species group, mercury content was significantly higher for bottom fish (0.17 +/- 0.10 microg g(-1) d.w.) than for pelagic (0.08 +/- 0.06 microg g(-1) d.w.), euryhaline fish (0.04 +/- 0.02 microg g(-1) d.w.), and crustacea (0.08 +/- 0.03 microg g(-1) d.w.). To understand the importance of mercury content of each prey group, we ran several theoretical scenarios assuming that chicks were fed on only one species at a time. Considering a diet restricted to lagoon (mostly benthic) prey, A- and B-chicks may encounter health problems with an excess of mercury. On the contrary, a diet restricted to marine (mostly pelagic) prey would decrease the mercury concentration in chick feathers; the fast growth rate and the related mercury dilution effect in little tern chicks seem to decrease mercury levels in their feathers. Our study supports the fact that marine pelagic prey are important for estuarine seabirds because they provide a food resource with lower contamination levels. This model may have a wider application in similar seabird species and coastal environments.