Local-scale impacts of extreme events drive demographic asynchrony in neighbouring top predator populations.

Extreme weather events are among the most critical aspects of climate change, but our understanding of their impacts on biological populations remains limited. Here, we exploit the rare opportunity provided by the availability of concurrent longitudinal demographic data on two neighbouring marine top predator populations (the black-browed albatross, Thalassarche melanophris, breeding in two nearby colonies) hit by an exceptionally violent storm during one study year. The aim of this study is to quantify the demographic impacts of extreme events on albatrosses and test the hypothesis that extreme events would synchronously decrease survival rates of neighbouring populations. Using demographic modelling we found that, contrary to our expectation, the storm affected the survival of albatrosses from only one of the two colonies, more than doubling the annual mortality rate compared to the study average. Furthermore, the effects of storms on adult survival would lead to substantial population declines (up to 2% per year) under simulated scenarios of increased storm frequencies. We, therefore, conclude that extreme events can result in very different local-scale impacts on sympatric populations. Crucially, by driving demographic asynchrony, extreme events can hamper our understanding of the demographic responses of wild populations to mean, long-term shifts in climate.

A central place foraging seabird flies at right angles to the wind to jointly optimize locomotor and olfactory search efficiency.

To increase the probability of detecting odour plumes, and so increase prey capture success, when winds are stable central place foraging seabirds should fly crosswind to maximize the round-trip distance covered. At present, however, there is no empirical evidence of this theoretical prediction. Here, using an extensive GPS tracking dataset, we investigate, for the first time, the foraging movements of Bulwer's petrels (Bulweria bulwerii) in the persistent North Atlantic trade winds. To test the hypotheses that, in stable winds, petrels use crosswind to maximize both the distance covered and the probability of detecting olfactory cues, we combine state-space models, generalized additive models and Gaussian plume models. Bulwer's petrels had the highest degree of selectivity for crosswinds documented to date, often leading to systematic zig-zag flights. Crosswinds maximized both the distance travelled and the probability of detecting odour plumes integrated across the round-trip (rather than at any given point along the route, which would result in energetically costly return flight). This evidence suggests that petrels plan round-trip flights at departure, integrating expected costs of homeward journeys. Our findings, which are probably true for other seabirds in similar settings, further highlight the critical role of wind in seabird foraging ecology.

Satellite tracking reveals sex-specific migration distance in green turtles (Chelonia mydas).

Satellite tracking is a key tool for studying sea turtles in the wild. Most tracking has been performed on adult females however, leaving knowledge gaps regarding other population segments, such as adult males. By satellite tracking 12 male green turtles (Chelonia mydas) at a breeding site in West Africa, we describe their movements from the breeding to the foraging grounds and compare migrations with those of 13 females tracked in the same season. During the mating period, some males remained near the focal nesting site, while others performed exploratory movements, apparently to visit other nearby rookeries. Males migrated on average shorter distances to foraging grounds (377 km, range 50-1081, n = 9) compared to females (1038 km, range 957-1850, n = 11]). Importantly, male foraging areas overlapped with previously described areas for females, suggesting sex-specific migration distances are not derived from differences in habitat selection. Strong support for differential migration by sex in sea turtles has hitherto been found in just one other species, but indications are that it may be a general feature in this group. These findings have important implications for our understanding of the interplay between reproductive roles and movement ecology of these emblematic animals.

Environmental variability directly affects the prevalence of divorce in monogamous albatrosses.

In many socially monogamous species, divorce is a strategy used to correct for sub-optimal partnerships and is informed by measures of previous breeding performance. The environment affects the productivity and survival of populations, thus indirectly affecting divorce via changes in demographic rates. However, whether environmental fluctuations directly modulate the prevalence of divorce in a population remains poorly understood. Here, using a longitudinal dataset on the long-lived black-browed albatross (Thalassarche melanophris) as a model organism, we test the hypothesis that environmental variability directly affects divorce. We found that divorce rate varied across years (1% to 8%). Individuals were more likely to divorce after breeding failures. However, regardless of previous breeding performance, the probability of divorce was directly affected by the environment, increasing in years with warm sea surface temperature anomalies (SSTA). Furthermore, our state-space models show that warm SSTA increased the probability of switching mates in females in successful relationships. For the first time, to our knowledge, we document the disruptive effects of challenging environmental conditions on the breeding processes of a monogamous population, potentially mediated by higher reproductive costs, changes in phenology and physiological stress. Environmentally driven divorce may therefore represent an overlooked consequence of global change.

Overlap between marine predators and proposed Marine Managed Areas on the Patagonian Shelf.

Static (fixed-boundary) protected areas are key ocean conservation strategies, and marine higher predator distribution data can play a leading role toward identifying areas for conservation action. The Falkland Islands are a globally significant site for colonial breeding marine higher predators (i.e., seabirds and pinnipeds). However, overlap between marine predators and Falkland Islands proposed Marine Managed Areas (MMAs) has not been quantified. Hence, to provide information required to make informed decisions regarding the implementation of proposed MMAs, our aims were to objectively assess how the proposed MMA network overlaps with contemporary estimates of marine predator distribution. We collated tracking data (1999-2019) and used a combination of kernel density estimation and model-based predictions of spatial usage to quantify overlap between colonial breeding marine predators and proposed Falkland Islands MMAs. We also identified potential IUCN Key Biodiversity Areas (pKBAs) using (1) kernel density based methods originally designed to identify Important Bird and Biodiversity Areas (IBAs) and (2) habitat preference models. The proposed inshore MMA, which extends three nautical miles from the Falkland Islands, overlapped extensively with areas used by colonial breeding marine predators. This reflects breeding colonies being distributed throughout the Falklands archipelago, and use being high adjacent to colonies due to central-place foraging constraints. Up to 45% of pKBAs identified via kernel density estimation were located within the proposed MMAs. In particular, the proposed Jason Islands Group MMA overlapped with pKBAs for three marine predator species, suggesting it is a KBA hot spot. However, tracking data coverage was incomplete, which biased pKBAs identified using kernel density methods, to colonies tracked. Moreover, delineation of pKBA boundaries were sensitive to the choice of smoothing parameter used in kernel density estimation. Delineation based on habitat model predictions for both sampled and unsampled colonies provided less biased estimates, and revealed 72% of the Falkland Islands Conservation Zone was likely a KBA. However, it may not be practical to consider such a large area for fixed-boundary management. In the context of wide-ranging marine predators, emerging approaches such as dynamic ocean management could complement static management frameworks such as MMAs, and provide protection at relevant spatiotemporal scales.

Costs of reproduction and migration are paid in later return to the colony, not in physical condition, in a long-lived seabird.

Life history theory suggests a trade-off between costly activities such as breeding and migration and somatic self-maintenance. However, how the short-term cost of parental effort is expressed in species with a slow pace-of-life is not well understood. Also, investigating carry-over effects of migration is most meaningful when comparing migratory strategies within the same population, but this has rarely been done. We explore this hypothesis in a long-lived, pelagic seabird, the Cory's Shearwater, Calonectris borealis, where males display partial migration. By manipulating reproductive effort and taking advantage of the natural variation in migratory strategy, we investigate whether early reproductive failure and migratory strategy had implications on the physical condition of males on return to the colony the following year. We experimentally induced breeding failure from mid-incubation, tracked the over-winter movements of these males and of males that invested in parental effort, and assessed innate immunity, stress, and residual body mass the following year. Early breeding failure resulted in earlier return to the colony among all males, associated with greater probability of reproductive success. Residents had a lower tail feather fault bar intensity, an indicator of stress during the non-breeding period, compared to migrants. Reproductive effort and migratory strategy had no impact on physiological condition otherwise. Our results provide evidence that in species with a slow-pace of life, such as the Cory's Shearwater, somatic maintenance is prioritised, with the costs of reproduction and migration paid in delayed arrival date.

Diet and trophic position of two mackerel species in the archipelago of Madeira, Portugal.

The Atlantic chub mackerel Scomber colias and the blue jack mackerel Trachurus picturatus are two abundant species in the Macaronesia region which includes the archipelago of Madeira, Portugal. Both are key species in the trophic web, being important prey for several local top predators, such as seabirds and marine mammals. Nonetheless, little is known about their feeding ecology in oceanic environments. In this study, the authors describe the seasonal variation in the diet of S. colias and T. picturatus in the oceanic region of Madeira throughout a year. Visual inspection of stomach contents revealed that S. colias fed on a broader range of prey groups than T. picturatus, but for both species, zooplankton (particularly calanoid copepods) and fish were the most important food items. The diet of S. colias included a higher proportion of fish, namely Atlantic saury Scomberesox saurus and S. colias, than that of T. picturatus, that included mostly the longspine snipefish Macroramphosus scolopax. T. picturatus consumed a higher proportion of decapods and other copepods. Seasonal variation was found in the diet of both species, with zooplanktonic species being more important in colder months (February to April) for S. colias and during warm months (May to October) for T. picturatus. Their diet in other seasons was dominated by fish. Although they consume similar prey, carbon and nitrogen stable isotope analysis of muscle of S. colias and T. picturatus showed little overlap in their diets, and T. picturatus showed higher δ15 N and a narrower isotopic niche.

Gadfly petrels use knowledge of the windscape, not memorized foraging patches, to optimize foraging trips on ocean-wide scales.

Seabirds must often travel vast distances to exploit heterogeneously distributed oceanic resources, but how routes and destinations of foraging trips are optimized remains poorly understood. Among the seabirds, gadfly petrels (Pterodroma spp.) are supremely adapted for making efficient use of wind energy in dynamic soaring flight. We used GPS tracking data to investigate the role of wind in the flight behaviour and foraging strategy of the Desertas petrel, Pterodroma deserta. We found that rather than visiting foraging hotspots, Desertas petrels maximize prey encounter by covering some of the longest distances known in any animal in a single foraging trip (up to 12 000 km) over deep, pelagic waters. Petrels flew with consistent crosswind (relative wind angle 60°), close to that which maximizes their groundspeed. By combining state-space modelling with a series of comparisons to simulated foraging trips (reshuffled-random, rotated, time-shifted, reversed), we show that this resulted in trajectories that were close to the fastest possible, given the location and time. This wind use is thus consistent both with birds using current winds to fine-tune their routes and, impressively, with an a priori knowledge of predictable regional-scale wind regimes, facilitating efficient flight over great distances before returning to the home colony.

Sex-specific telomere length and dynamics in relation to age and reproductive success in Cory's shearwaters.

Individuals in free-living animal populations generally differ substantially in reproductive success, lifespan and other fitness-related traits, but the molecular mechanisms underlying this variation are poorly understood. Telomere length and dynamics are candidate traits explaining this variation, as long telomeres predict a higher survival probability and telomere loss has been shown to reflect experienced "life stress." However, telomere dynamics among very long-lived species are unresolved. Additionally, it is generally not well understood how telomeres relate to reproductive success or sex. We measured telomere length and dynamics in erythrocytes to assess their relationship to age, sex and reproduction in Cory's shearwaters (Calonectris borealis), a long-lived seabird, in the context of a long-term study. Adult males had on average 231 bp longer telomeres than females, independent of age. In females, telomere length changed relatively little with age, whereas male telomere length declined significantly. Telomere shortening within males from one year to the next was three times higher than the interannual shortening rate based on cross-sectional data of males. Past long-term reproductive success was sex-specifically reflected in age-corrected telomere length: males with on average high fledgling production were characterized by shorter telomeres, whereas successful females had longer telomeres, and we discuss hypotheses that may explain this contrast. In conclusion, telomere length and dynamics in relation to age and reproduction are sex-dependent in Cory's shearwaters and these findings contribute to our understanding of what characterises individual variation in fitness.

An ontogenetic perspective on migratory strategy of a long-lived pelagic seabird: Timings and destinations change progressively during maturation.

The processes that drive the ontogeny of migratory strategies in long-lived animals with slow maturation remain enigmatic. While some short-lived migrants are known or believed to repeat the same migratory patterns throughout their lives, little is known on the time required for immature long-lived migrants to progressively acquire adult-like migratory behaviours, or which aspects take longer to refine during the maturation process. Here, we studied the ontogeny of long-distance migratory strategies and related patterns of spatial distribution in a long-lived seabird species during the annual cycle. To do so, we deployed light-level geolocators on 4- to 9-year-old immature Cory's shearwaters (Calonectris borealis) and on breeding adults. We revealed that migratory timings and destinations of young shearwaters progressively changed with age. The effect of ageing was remarkably evident on spring migratory performance and phenology. Birds gradually shortened the duration of the non-breeding period by advancing departure date and reducing travelling time, which resulted in a sequential arrival at the colony of the various age contingents. Ageing immatures gradually changed from a more exploratory strategy to a more conservative way of exploiting resources, reducing both their year-round spatial spread across oceanic domains and the total distance travelled. Immatures always performed a trans-equatorial migration to the Southern Hemisphere, contrasting with 17% of the adults which remained in the North Atlantic year-round. Finally, during the breeding season immatures were widely dispersed through the North Atlantic reducing their overlap with breeding adults. Our long-term study provides empirical support to the hypothesis that in long-lived species, the refinement of migratory behaviour and year-round spatial distribution is a progressive process mediated by age and experience, where life stage constraints and competition for resources may also play a role. The emerging pattern suggests that for some avian taxa, the ontogeny of migratory strategy is a prolonged, complex and dynamic process.

The importance of migratory connectivity for global ocean policy.

The distributions of migratory species in the ocean span local, national and international jurisdictions. Across these ecologically interconnected regions, migratory marine species interact with anthropogenic stressors throughout their lives. Migratory connectivity, the geographical linking of individuals and populations throughout their migratory cycles, influences how spatial and temporal dynamics of stressors affect migratory animals and scale up to influence population abundance, distribution and species persistence. Population declines of many migratory marine species have led to calls for connectivity knowledge, especially insights from animal tracking studies, to be more systematically and synthetically incorporated into decision-making. Inclusion of migratory connectivity in the design of conservation and management measures is critical to ensure they are appropriate for the level of risk associated with various degrees of connectivity. Three mechanisms exist to incorporate migratory connectivity into international marine policy which guides conservation implementation: site-selection criteria, network design criteria and policy recommendations. Here, we review the concept of migratory connectivity and its use in international policy, and describe the Migratory Connectivity in the Ocean system, a migratory connectivity evidence-base for the ocean. We propose that without such collaboration focused on migratory connectivity, efforts to effectively conserve these critical species across jurisdictions will have limited effect.

Genomics detects population structure within and between ocean basins in a circumpolar seabird: The white-chinned petrel.

The Southern Ocean represents a continuous stretch of circumpolar marine habitat, but the potential physical and ecological drivers of evolutionary genetic differentiation across this vast ecosystem remain unclear. We tested for genetic structure across the full circumpolar range of the white-chinned petrel (Procellaria aequinoctialis) to unravel the potential drivers of population differentiation and test alternative population differentiation hypotheses. Following range-wide comprehensive sampling, we applied genomic (genotyping-by-sequencing or GBS; 60,709 loci) and standard mitochondrial-marker approaches (cytochrome b and first domain of control region) to quantify genetic diversity within and among island populations, test for isolation by distance, and quantify the number of genetic clusters using neutral and outlier (non-neutral) loci. Our results supported the multi-region hypothesis, with a range of analyses showing clear three-region genetic population structure, split by ocean basin, within two evolutionary units. The most significant differentiation between these regions confirmed previous work distinguishing New Zealand and nominate subspecies. Although there was little evidence of structure within the island groups of the Indian or Atlantic oceans, a small set of highly-discriminatory outlier loci could assign petrels to ocean basin and potentially to island group, though the latter needs further verification. Genomic data hold the key to revealing substantial regional genetic structure within wide-ranging circumpolar species previously assumed to be panmictic.

Climate change resilience of a globally important sea turtle nesting population.

Few studies have looked into climate change resilience of populations of wild animals. We use a model higher vertebrate, the green sea turtle, as its life history is fundamentally affected by climatic conditions, including temperature-dependent sex determination and obligate use of beaches subject to sea level rise (SLR). We use empirical data from a globally important population in West Africa to assess resistance to climate change within a quantitative framework. We project 200 years of primary sex ratios (1900-2100) and create a digital elevation model of the nesting beach to estimate impacts of projected SLR. Primary sex ratio is currently almost balanced, with 52% of hatchlings produced being female. Under IPCC models, we predict: (a) an increase in the proportion of females by 2100 to 76%-93%, but cooler temperatures, both at the end of the nesting season and in shaded areas, will guarantee male hatchling production; (b) IPCC SLR scenarios will lead to 33.4%-43.0% loss of the current nesting area; (c) climate change will contribute to population growth through population feminization, with 32%-64% more nesting females expected by 2120; (d) as incubation temperatures approach lethal levels, however, the population will cease growing and start to decline. Taken together with other factors (degree of foraging plasticity, rookery size and trajectory, and prevailing threats), this nesting population should resist climate change until 2100, and the availability of spatial and temporal microrefugia indicates potential for resilience to predicted impacts, through the evolution of nest site selection or changes in nesting phenology. This represents the most comprehensive assessment to date of climate change resilience of a marine reptile using the most up-to-date IPCC models, appraising the impacts of temperature and SLR, integrated with additional ecological and demographic parameters. We suggest this as a framework for other populations, species and taxa.

Absence of haemosporidian parasite infections in the long-lived Cory's shearwater: evidence from molecular analyses and review of the literature.

The apparent scarcity or absence of blood parasites in some avian groups, such as seabirds, has been related to intrinsic and extrinsic factors including host immunological capacity, host-parasite assemblage, and ecological parameters, but also to reduced sensitivity of some methods to detect low parasite prevalence/intensities of infection. Here, we examined the haemosporidian parasite prevalence in a breeding population of Cory's shearwater Calonectris diomedea borealis, a long-distance migrant seabird, nesting in the Macaronesian region, in the Eastern Atlantic. Previous studies on Calonectris diomedea complex were based on small sample sizes providing weak evidence for a lack of infections by haemoparasites. Here, we investigated the presence of both parasite infections in C. d. borealis and larvae of potential mosquito vectors on the area. By employing a PCR-based assay, we extensively examined the prevalence of blood parasites belonging to the genera Plasmodium, Haemoproteus, and Leucocytozoon in 286 individuals from different life stages (i.e., chicks, immatures, sabbatical, and breeding adults), facing their specific energetic trade-offs (immunological functions vs. life history activities). We sampled immatures and adult shearwaters, of different sexes, ages, and migratory origins, from two sub-colonies. None of the sampled individuals were infected by these parasites, supporting the hypothesis that there was no in situ or ex situ transmission of vector-borne parasites in marine habitats irrespective of host's life stage and in spite of the presence of the potential Plasmodium vector Culiseta longiareolata breeding in the area. These results suggest that the lack of transmission of haemosporidian parasites on Selvagem Grande may be related to the lack of suitable dipteran vectors at the study sites, which may result from the geographic isolation of this area.

High occurrence of jellyfish predation by black-browed and Campbell albatross identified by DNA metabarcoding.

Gelatinous zooplankton are a large component of the animal biomass in all marine environments, but are considered to be uncommon in the diet of most marine top predators. However, the diets of key predator groups like seabirds have conventionally been assessed from stomach content analyses, which cannot detect most gelatinous prey. As marine top predators are used to identify changes in the overall species composition of marine ecosystems, such biases in dietary assessment may impact our detection of important ecosystem regime shifts. We investigated albatross diet using DNA metabarcoding of scats to assess the prevalence of gelatinous zooplankton consumption by two albatross species, one of which is used as an indicator species for ecosystem monitoring. Black-browed and Campbell albatross scats were collected from eight breeding colonies covering the circumpolar range of these birds over two consecutive breeding seasons. Fish was the main dietary item at most sites; however, cnidarian DNA, primarily from scyphozoan jellyfish, was present in 42% of samples overall and up to 80% of samples at some sites. Jellyfish was detected during all breeding stages and consumed by adults and chicks. Trawl fishery catches of jellyfish near the Falkland Islands indicate a similar frequency of jellyfish occurrence in albatross diets in years of high and low jellyfish availability, suggesting jellyfish consumption may be selective rather than opportunistic. Warmer oceans and overfishing of finfish are predicted to favour jellyfish population increases, and we demonstrate here that dietary DNA metabarcoding enables measurements of the contribution of gelatinous zooplankton to the diet of marine predators.

Sex and migratory strategy influence corticosterone levels in winter-grown feathers, with positive breeding effects in a migratory pelagic seabird.

To overcome unpredictable stressful transitory events, animals trigger an allostatic response involving the hypothalamic-pituitary-adrenal cortex. This hormonal response, which involves the release of glucocorticoids which in turn mediate between the main physiological mechanisms that regulate the energetic demands and resource allocation trade-off with behavioural responses to environmental perturbations and may ultimately lead to variation in fitness. We have used the Cory's shearwater Calonectris borealis, a sexually dimorphic pelagic seabird with a partial migratory strategy, as a model bird species to analyse a number of traits related to the stress response. We investigated whether the activation of a stressful response, mediated by corticosterone, during the wintering period (1) correlated with the previous breeding success, (2) was affected by the migratory behaviour of male birds and (3) had consequences in the fitness of the birds. Corticosterone levels in feathers grown overwinter were analysed in 61 adult birds during three consecutive migratory periods (2009-2012) and in 14 immature birds in the wintering period 2010-2011. Moreover, the levels of corticosterone were analysed in experimental birds which were freed from their reproductive duties and compared with control birds which raised fledglings to the end of the breeding period. The results show that the levels of corticosterone were sex dependent, differed between years and were affected by the migratory strategy performed by the birds. The activation of the stressful response over the wintering period generated residual carry-over effects that positively affected the reproductive output in the subsequent breeding stage, a phenomenon previously undescribed in a long-lived pelagic seabird. Our study provides evidence that the analysis of corticosterone from feathers is a useful tool to evaluate carry-over effects in birds far away from breeding sites, opening new possibilities for future studies in this field.

Provenance does matter: links between winter trophic segregation and the migratory origins of European robins.

Amongst migratory species, it is common to find individuals from different populations or geographical origins sharing staging or wintering areas. Given their differing life histories, ecological theory would predict that the different groups of individuals should exhibit some level of niche segregation. This has rarely been investigated because of the difficulty in assigning migrating individuals to breeding areas. Here, we start by documenting a broad geographical gradient of hydrogen isotopes (δ 2H) in robin Erithacus rubecula feathers across Europe. We then use δ 2H, as well as wing-tip shape, as surrogates for broad migratory origin of birds wintering in Iberia, to investigate the ecological segregation of populations. Wintering robins of different sexes, ages and body sizes are known to segregate between habitats in Iberia. This has been attributed to the despotic exclusion of inferior competitors from the best patches by dominant individuals. We find no segregation between habitats in relation to δ 2H in feathers, or to wing-tip shape, which suggests that no major asymmetries in competitive ability exist between migrant robins of different origins. Trophic level (inferred from nitrogen isotopes in blood) correlated both with δ 2H in feathers and with wing-tip shape, showing that individuals from different geographic origins display a degree of ecological segregation in shared winter quarters. Isotopic mixing models indicate that wintering birds originating from more northerly populations consume more invertebrates. Our multi-scale study suggests that trophic-niche segregation may result from specializations (arising in the population-specific breeding areas) that are transported by the migrants into the shared wintering grounds.

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.

Allochrony is shaped by foraging niche segregation rather than adaptation to the windscape in long-ranging seabirds.

BACKGROUND: Ecological segregation allows populations to reduce competition and coexist in sympatry. Using as model organisms two closely related gadfly petrels endemic to the Madeira archipelago and breeding with a two month allochrony, we investigated how movement and foraging preferences shape ecological segregation in sympatric species. We tested the hypothesis that the breeding allochrony is underpinned by foraging niche segregation. Additionally, we investigated whether our data supported the hypothesis that allochrony is driven by species-specific adaptations to different windscapes. METHODS: We present contemporaneous tracking and stable isotopes datasets for Zino's (Pterodroma madeira) and Desertas (Pterodroma deserta) petrels. We quantified the year-round distribution of the petrels, characterised their isotopic niches and quantified their habitat preferences using machine learning (boosted regression trees). Hidden-Markov-models were used to investigate the effect of wind on the central-place movement speed, and a simulation framework was developed to investigate whether each species breeds at times when the windscape is most favourable to sustain their trips. RESULTS: Despite substantial spatial overlap throughout the year, the petrels exhibited diverging isotopic niches and habitat preferences during breeding. Both species used a vast pelagic region in the North Atlantic, but targeted two different mesopelagic ecoregions and showed a preference for habitats mostly differing in sea surface temperature values. Based on our simulation framework, we found that both species would perform trips of similar speed during the other species' breeding season. CONCLUSIONS: The different breeding schedules between the species are underpinned by differences in foraging habitat preferences and adaptation to the local environment, rather than to the windscape. Nevertheless, the larger Desertas petrels exploited significantly windier conditions, potentially unsustainable for the smaller Zino's petrels. Furthermore, due to larger mass and likely higher fasting endurance, Desertas petrels engaged in central-place-foraging movements that covered more ground and lasted longer than those of Zino's petrels. Ultimately, patterns of ecological segregation in sympatric seabirds are shaped by a complex interplay between foraging and movement ecology, where morphology, foraging trip regulation and fasting endurance have an important- yet poorly understood- role.

Carry-over effects from breeding modulate the annual cycle of a long-distance migrant: an experimental demonstration.

Carry-over effects relate to events or processes that influence individual performance in a subsequent season, but their occurrence in the annual cycle of migratory avian taxa is seldom studied. We investigated if different levels of resource allocation to reproduction may result in carry-over effects that change the timing and destination of long-distance migration. We reduced the parental investment of Cory's Shearwaters Calonectris diomedea by removing their chick at an early stage. When compared to individuals with greater parental investment (controls that raised chicks to close to fledging), manipulated birds started most stages of migration sooner and returned to the colony earlier at the start of the following breeding season. Late arrival in the subsequent nesting season increased the probability of skipping a breeding year. Manipulated males were less likely to engage in long-distance migration, which supports the idea that partial migration is condition dependent. Our study demonstrates experimentally that energetic or time-dependent costs of reproduction may have an enduring impact on migration schedule and on nonbreeding geographical distribution of long-distance migrants, which may also influence the ability to breed in the following season.