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.FEDER; FCT-Fundação para a Ciência e Tecnologiainfo:eu-repo/semantics/publishedVersio

Global changes in coastal wetlands of importance for non-breeding shorebirds

Shorebird declines are occurring worldwide but the causes are not fully understood. Recent literature suggests that the deterioration of habitat quality at their non-breeding areas, mostly located in temperate and tropical coastal wetlands, might be a major contributing factor. However, most studies carried out so far tend to be restricted to a few regions. Remote sensing can help correct such geographical bias on knowledge by providing a standardized approach on how shorebird habitats have been changing over the last few decades at a global scale. Here we analyzed time series of remote sensing classifications of tidal flats and land cover to quantify worldwide habitat changes in coastal Important Bird and Biodiversity Areas (IBAs) relevant for non-breeding shorebirds over the last two decades. Globally, supratidal areas (used as roosting habitat) have changed more significantly than tidal flats (used as feeding habitat). Yet, we found striking losses of tidal flats in IBAs distributed in several regions of the East Asian - Australasian Flyway. At supratidal areas, there was a general expansion of marshland, grassland and urban areas, contrasting with a decline of barren land, woodland and cropland. The expansion of marshland occurred in IBAs of most regions of the world. Urban areas also expanded consistently in supratidal areas within the most populated regions of the world. The loss of barren land is particularly concerning as it may translate into a loss of high-quality roosts and it was highly frequent in IBAs of all migratory flyways. Overall, our results confirm the large losses of shorebird habitat in the East Asian - Australasian Flyway reported in the literature, and highlight unreported generalized changes in supratidal habitats, such as the expansion of marshland and the loss of barren land, that may have negative implications for shorebirds, deserving further research and consideration in conservation programs.info:eu-repo/semantics/publishedVersio

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.Fundação para a Ciência e Tecnologia - FCTinfo:eu-repo/semantics/publishedVersio

Colony attendance and moult pattern of Cory's Shearwaters (Calonectris borealis) differing in breeding status and age

Migratory birds must fit three costly life-history events within the annual cycle, reproduction, moult and migration, to minimize their overlap and maximize survival and breeding success. However, some seabirds, such as Cory’s Shearwater Calonectris borealis, overlap body moult and breeding, with flight feather renewal occurring in late chick-rearing. In contrast, the moult patterns of non-breeding adult (sabbatical) and immature Cory’s Shearwaters, which also attend the colony during the breeding season, remain poorly understood. Furthermore, the potential implications of life-stage and breeding status trade-offs on moult status and colony attendance in non-breeders has rarely been investigated. Surveying different areas within one colony between June and September 2013 and 2014, we studied the age and breeding status composition of birds attending the breeding colony and scored moult of their body (breast and upper-neck), wing and tail feathers. We found that in addition to breeders (n = 165), 57.6% of the birds (n = 389) attending the colony were 4- to 10-year-old immatures (n = 132) and adult sabbatical shearwaters (n = 92). Sabbaticals and 8- to 10-year-old immatures (n = 28) were present at the colony during incubation, whereas only three sabbatical birds and no 8- to 10-year-old immatures were captured in late chick-rearing. Conversely, 4- to 7-year-old immatures arrived later in the season but were still present in late chick-rearing. Sabbatical and 8- to 10-year-old immatures were moulting body feathers at the same time as adult breeders, whereas, among 4- to 7-year-old immatures, older birds moulted earlier than younger birds. A larger proportion of sabbatical birds were replacing tail feathers compared with adult breeders. However, there was no evidence that sabbaticals or 8- to 10-year-old immatures differed in wing moult from adult breeders until August. Overall, our study shows that colony attendance by non-breeding adults and immatures is widespread in this population. The synchronous moult schedule of flight and body feathers across age groups at different life-history stages may suggest that this aspect of moult is controlled by environmental conditions.Fundação para a Ciência e Tecnologia - FCTinfo:eu-repo/semantics/publishedVersio

Characterization of an extinct seabird colony on the island of Santa Luzia (Cabo Verde) and its potential for future recolonizations

Islands worldwide have sufered seabird extinctions after the arrival of humans and the alien species they introduced. On Santa Luzia (Cabo Verde), an uninhabited island of 35 km2 ,the presence of an impressive quantity of petrel bones in coastal dunes suggested the previous existence of an important seabird colony. Yet, these remains had not been identifed and no seabird extinctions have been reported for the island. This paper characterizes the extinct seabird colony of Santa Luzia and discusses the chronology and possible causes of its demise. A total of 130 grid points in a 5 km2 area and 38 supplementary points within and outside the main study area were excavated to collect bone remains. A total of 1318 anatomical elements, identifed as White-faced Storm Petrel Pelagodroma marina eadesorum (85.3% of the minimum number of individuals, MNI), Boyd’s Shearwater Pufnus lherminieri boydi (11.8% MNI) and Cape Verde Storm Petrel Hydrobates jabejabe (2.9% MNI), were found in 18% of the sampling points, within 1.25 km2 . Neither of the two former species currently breeds on Santa Luzia. In addition, two bones of the Cape Verde Shearwater Calonectris edwardsii and Pterodroma sp. were detected in the supplementary points. Radiocarbon dating of White-faced Storm Petrel (n=10) and Boyd’s Shearwater bones (n=13) suggests that the colony probably went extinct during the frst half of the twentieth century. The recent extinction of these species on Santa Luzia might be consequent on the arrival of humans and their domestic animals on the island. We estimate that the extinct seabird populations must have been at least hundreds of thousand strong, far larger than current populations of the same species in Cabo Verde. We suggest that, following feral cat eradication, Santa Luzia has a signifcant potential for seabird restorationFundação para a Ciência e Tecnologia - FCTinfo:eu-repo/semantics/publishedVersio

Evidence for trophic differences between live and bycatch oceanic juvenile loggerhead sea turtles

The loggerhead sea turtle Caretta caretta is a vulnerable migratory species that spends its frst years of life in the open sea. During this developmental phase, loggerheads can be found foraging in the epipelagic zone of the waters surrounding the Madeira Archipelago, providing a rare opportunity to gather information on the ecology of its oceanic developmental stage. In this study, we characterized the isotopic niche of these juveniles, using stable isotope analysis. We assessed two groups of turtles, turtles captured alive (n=24) and turtles captured as bycatch on local longlines (n=12), and explored whether animals caught in the local fshing gear represented a random sample of the population, or whether there is some evidence for a specialized foraging behaviour. We found that turtle bycatch had a signifcantly higher mean stable nitrogen isotope value in whole blood (δ15N=8.5±0.6‰ SD) compared to the group of turtles captured alive in the same period (δ15N=7.6±0.5‰ SD), indicating that they had a diferent diet. While there was a tendency for turtle bycatch to be slightly larger, we found no efect of body size on δ15N values. We propose a distinct foraging behaviour strategy hypothesis, with a group of turtles being more susceptible to interactions with fsheries and thus having a higher mortality risk, which should motivate the implementation of existing guidelines to reduce sea turtle bycatch.info:eu-repo/semantics/publishedVersio

Revealing the foraging movements and diet of the White-faced Storm Petrel Pelagodroma marina in the NE Atlantic

The White-faced Storm Petrel (WFSP) Pelagodroma marina has a widespread distribution, although virtually nothing is known about their feeding ecology and distributions at-sea. To describe their foraging areas, a total of 77 birds were equipped with 1 g-GPS loggers on Selvagem Grande, Madeira, Portugal (30° 09′ N, 15° 52′ W), during the 2018 and 2019 breeding seasons. We also assessed the diet of WFSP by analysing 17 faecal samples from chicks and 1 regurgitation from an adult using DNA metabarcoding techniques. Additionally, we collected body feathers from ten WFSP chicks to determine mercury concentration. WFSP fed mainly in deep oceanic waters, travelling up to 400 km from the colony, and did not concentrate in any well-defned, population-level foraging hotspots. Some individuals foraged along the edge of the shelf, near the African coast and the Canary Islands, especially during chick rearing. The duration of foraging trips and the total distance travelled, were, on average, 5.1 days and 723 km during the incubation period and 3.0 days and 578 km during chick rearing. The diet of WFSP was dominated by fsh and cephalopods (crustacean prey were not detected), with Myctophidae (FO=71%) representing the main fsh family. WFSP often consume mesopelagic fsh, in line with their preference for deep oceanic waters and with a small diference in at sea behavior (i.e., travel speed) between the diurnal and nocturnal period. The relatively high concentrations of mercury accumulated in body feathers of WFSP chicks (3.45±1.44 mg kg−1 dry weight; range 1.68–6.01 mg kg−1) support the idea that WFSP raise their chicks mostly on mesopelagic prey from deep pelagic areas.CESAM; Fundação para a Ciência e Tecnologia - FCTinfo:eu-repo/semantics/publishedVersio

Higher mercury contamination is associated with shorter telomeres in a long-lived seabird – A direct effect or a consequence of among-individual variation in phenotypic quality?

Mercury is a heavy metal, which is pervasive and persistent in the marine environment. It bioaccumulates within organisms and biomagnifies in the marine food chain. Due to its high toxicity, mercury contamination is a major concern for wildlife and human health. Telomere length is a biomarker of aging and health, because it predicts survival, making it a potential tool to investigate sublethal effects of mercury contamination. However, the relationship between telomeres and mercury contamination is unclear. We measured feather mercury concentration in Cory's Shearwaters Calonectris borealis, long-lived seabirds and top predators, between 9 and 35 years of age and related it to telomere length in erythrocytes. Cory's Shearwaters with higher mercury concentrations had shorter telomeres and the effect was sex-dependent, reaching significance in males only. This may be explained by the fact that males have longer telomeres and higher and more variable mercury concentrations than females in this population. The mercury effect on telomere length was stronger on longer telomeres in the genome within individuals. We discuss the hypotheses that the negative correlation could either be a direct effect of mercury on telomere shortening and/or a consequence of variation in phenotypic quality among individuals that results in a covariation between mercury contamination and telomere length.Fundação para a Ciência e Tecnologia - FCTinfo:eu-repo/semantics/publishedVersio

Invisible trophic links?:Quantifying the importance of non-standard food sources for key intertidal avian predators in the Eastern Atlantic

Coastal wetlands are heterogeneous systems with multiple inputs and complex interactionswithin local food webs. Interpreting such complexity is limited by incomplete knowledgeof trophic interactions among organisms. Although widely recognized as secondary consumersand predators of intertidal macroinvertebrates, shorebirds can also consume lower-trophic-levelfood sources, and frequently forage in adjacent supratidal habitats. To ascertain potential trophiclinks between overwintering shorebirds and alternative non-standard food sources, we collectedcarbon and nitrogen stable isotope data of shorebirds and benthic organisms from 4 coastal wetlandsalong the Eastern Atlantic: Tejo Estuary, Portugal; Sidi-Moussa, Morocco; Banc d’Arguin,Mauritania; and Bijagós Archipelago, Guinea-Bissau. Using dual-isotope Bayesian mixing models,we evaluated the relative importance of intertidal benthic macroinvertebrates and 3 otherpotential food sources (biofilm and seagrass rhizomes from intertidal areas, and saltpan macroinvertebrates)in the diet of wintering shorebirds. Although intertidal macroinvertebrates form themain part of most shorebird species’ diet, our data revealed that supratidal saltpans can contributeto >30% of the biomass ingested by several shorebird species. Seagrass rhizomes represented>10% of the diet of several species in Banc d’Arguin and in Sidi Moussa. Little stint Calidris minutaappears to consume biofilm on all 3 wetlands where they were sampled, which is the first timebiofilm consumption by shorebirds has been detected along the East Atlantic Flyway. Empiricalevidence for generalized consumption of alternative food sources by intertidal avian predatorsshow the greater complexity and food web connectivity in and of intertidal habitats, and also withthe surrounding habitats

Individual variability in the migratory path and stopovers of a long-distance pelagic migrant

The analysis of repeated journeys of the same individuals is becoming an important tool in the study of animal migration. This approach has been used to analyse the migratory consistency (in schedules, routes and stopovers) of various species, with implications for the understanding of navigation mechanisms, travel strategies and conservation. However, few studies have addressed the individual consistency in pelagic long-distance migrations, in particular in the routes followed in different years. By analysing 100 journeys from 35 individual Cory’s shearwaters, Calonectris diomedea, that repeatedly migrated to the South African region we examined the fidelity to migratory paths and stopovers of a transequatorial seabird migrant. Cory’s shearwaters showed an overall trend to be faithful to their routes in different years, which was particularly obvious in the first (southbound) part of the outward migration. Nevertheless, we did not detect any individual consistency in the final part of the outward migration, in the return migration or in the location of the stopovers. The fact that Cory’s shearwaters can be either consistent or inconsistent in different parts of their routes is possibly related to the variability of the external factors (such as wind conditions and location of good foraging areas) found along the way. 2013 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved