There is growing evidence that migratory species are particularly vulnerable to rapid environmental changes arising from human activity. Species are expected to vary in their capacity to respond to ...these changes: long-distance migrants and those lacking variability in migratory traits are probably at considerable disadvantage. The few studies that have assessed the degree of plasticity in behaviour of marine animals suggest that fidelity to non-breeding destinations is usually high. In the present study, we evaluated individual flexibility in migration strategy of a highly pelagic seabird, the Cory's shearwater Calonectris diomedea. Geolocation data from 72 different migrations, including 14 birds that were tracked for more than one non-breeding season, showed a remarkable capacity to change winter destinations between years. Although some birds exhibited high site fidelity, others shifted from the South to North Atlantic, from the western to eastern South Atlantic, and from the Atlantic to Indian Ocean. Individuals also showed flexibility in stopover behaviour and migratory schedule. Although their K-selected life-history strategy has the disadvantage that the chances of microevolution are slight if circumstances alter rapidly, these results suggest that Cory's shearwaters may be in a better position than many other long-distance migrants to face the consequences of a changing environment.
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.
Around fifteen thousand fieldworkers annually count breeding birds using standardized protocols in 28 European countries. The observations are collected by using country-specific and standardized ...protocols, validated, summarized and finally used for the production of continent-wide annual and long-term indices of population size changes of 170 species. Here, we present the database and provide a detailed summary of the methodology used for fieldwork and calculation of the relative population size change estimates. We also provide a brief overview of how the data are used in research, conservation and policy. We believe this unique database, based on decades of bird monitoring alongside the comprehensive summary of its methodology, will facilitate and encourage further use of the Pan-European Common Bird Monitoring Scheme results.
Few studies have assessed the effectiveness of the Protected Area networks on the conservation status of target species. Here, we assess the effectiveness of the Portuguese Natura 2000 (the European ...Union network of protected areas) in maintaining a species included in the Annex I of the Bird Directive, namely the population of a priority farmland bird, the little bustard
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We measured the effectiveness of the Natura 2000 by comparing population trends across time (2003-2006 and 2016) in 51 areas, 21 of which within 12 Special Protection Areas (SPA) that were mostly designated for farmland bird conservation and another 30 areas without EU protection.
Overall, the national population is estimated to have declined 49% over the last 10-14 years. This loss was found to be proportionally larger outside SPA (64% decline) compared to losses within SPA (25% decline). However, the absolute male density decline was significantly larger within SPA .
In spite of holding higher population densities and having prevented habitat loss, we conclude that Natura 2000 was not effective in buffering against the overall bustard population decline. Results show that the mere designation of SPA in farmland is not enough to secure species populations and has to be combined with agricultural policies and investment to maintain not only habitat availability but also habitat quality.
Bycatch is one of the main threats to seabird conservation. In Portugal, there are alarming estimates of seabirds bycaught per year in bottom gillnet fisheries, which get entangled during fishing ...operations, when the gear is close to the surface. In this study, a visual deterrent (scarybird) was tested in a fishing vessel operating bottom gillnets near and within Berlengas Islands SPA (Special Protection Area). Trials were conducted between 2019 and 2020, with 18 control and experimental fishing trips monitored by a trained observer. The scarybird proved to be an effective bird deterrent measure, affecting both the numbers and distribution of seabirds and keeping a large portion of birds away from the vessel during fishing operations, making them potentially less vulnerable to bycatch. The deterrent device was more effective in the closest area to the vessel (0–20 m) where there was a significant reduction in the number of gulls (Larus michahellis/fuscus, −56 %) and northern gannets (Morus bassanus, −72 %) close to the vessel, by comparison to control fishing trips. The use of this aerial deterrent device had no impact on the fishery's target catches and revenue, which contributed to a good acceptance by fishermen. This simple and “easy to implement” deterrent device has potential to be further tested as a bycatch mitigation measure in bottom gillnets but also in other gears, whenever interactions with birds occur mainly close to the surface.
The replacement of old feathers is essential for birds, but it is also an energy-demanding task. As moult usually does not coincide with other stressful events in its annual cycle, such as ...reproduction and migration, the bird can optimise its use of time and energy allocated to different activities. There are very few studies comparing the moult strategies of populations with similar breeding calendars but occurring in areas of different habitat quality. Cory's Shearwaters Calonectris diomedea have a partial moult-breeding overlap, an unusual phenomenon among pelagic seabirds. We have compared the moult schedules in Cory's Shearwater colonies located in distinct environments (pelagic vs. coastal) and show that moult-breeding overlap is less extensive on Selvagem Grande, situated in deep oceanic waters, than on Berlenga, situated on the continental shelf. Colony attendance of failed breeders, most of which were moulting, was lower at Selvagem Grande than at Berlenga, which suggests that the feeding areas of birds from the former site are more distant from the colony. Failed breeders started to moult earlier than individuals still raising a chick, and breeding status had a stronger influence on determining the onset of wing-feather moult than colony location. Despite published evidence that internal circannual rhythms and external cues, such as variation in daylength, are important factors regulating moult schedules, it is clear that birds retain a considerable flexibility that allows them to respond to external factors in order to strategically manage time and energy in a way that is thought to maximise their fitness.
The COVID-19 pandemic has likely affected natural systems around the world; the curtailment of human activity has also affected the collection of data needed to identify the indirect effects of this ...pandemic on natural systems. We describe how the outbreak of COVID-19 disease, and associated stay-at-home orders in four political regions, have affected the quantity and quality of data collected by participants in one volunteer-based bird monitoring project, eBird. The four regions were selected both for their early and prolonged periods of mandated changes to human activity, and because of the high densities of observations collected. We compared the months of April 2020 with April in previous years. The most notable change was in the landscapes in which observations were made: in all but one region human-dominated landscapes were proportionally more common in the data in April 2020, and observations made near the rarer wetland habitat were less prevalent. We also found subtler changes in quantity of data collected, as well as in observer effort within observation periods. Finally, we found that these effects of COVID-19 disease varied across the political units, and thus we conclude that any analyses of eBird data will require region-specific examination of whether there have been any changes to the data collection process during the COVID-19 pandemic that would need to be taken into account.
•eBird citizen science/community science data have many conservation applications.•Collection of these data has been altered during the COVID-19 pandemic.•A greater proportion of observations have been made in urbanized landscapes.•Other aspects of observation effort have also been altered during the pandemic.•Extracting biological insights from the data must account for these changes.
Several species of seabirds show cyclic patterns of attendance at their nesting colonies. We examined the patterns of variation in the numbers of Cory's shearwater at three colonies (two oceanic and ...one located on the continental shelf), including the world's largest, at Selvagem Grande, Madeira, Portugal and considered several hypotheses concerning their causal mechanisms. At Selvagem Grande, cycles were exceptionally marked and regular, with a periodicity ranging from 7.8 to 11 days, and involved both breeders and nonbreeders. In contrast, variation in numbers was aperiodic at a nearby and much smaller colony (Selvagem Pequena), and also at the colony located off the Portuguese coast (Berlenga Island). We found no relationships between number of birds ashore and environmental variables such as wind direction and speed or lunar cycle. Cycles did not seem to be driven by oscillations in food availability or accessibility, given that they did not correlate with daily chick growth rates (which were acyclic) or diet. Despite their regularity, cycles were slightly out of phase in different sectors of Selvagem Grande, which suggests that social interactions at the colony could act as an entrainment agent for an endogenous rhythm, and so cycles are probably more likely to occur in large and dense colonies. Observations are consistent with the hypothesis that cycles facilitate social interactions by maximizing the probability of encounters at the colony. However, the exact mechanisms through which these remarkable cycles are controlled are still completely unknown, and clearly further research is needed.
Many oceanic areas are still in need of baseline information on their structure and functioning. This is particularly important due to the ever-increasing impacts of global changes, which have led to ...the decline of marine life, and top predators in particular. The study of the structure and functioning of food webs can help understand the consequences of the disappearance of this group in marine ecosystems. Here, we develop a mass-balanced model for the marine Exclusive Economic Zone of the archipelago of Madeira, with emphasis on the role of marine megafauna in this ecosystem. A total of 50 functional groups were defined, representing coastal and open ocean areas, and epipelagic and deep-sea levels. The total biomass of the Madeira system was calculated at 52.68 t km−2, with lower trophic level organisms comprising 89.9 % of its biomass. Marine megafauna, namely pelagic sharks and coastal birds had the highest impacts across other trophic levels and were classified as keystone species, together with monk seals. The food web was characterized by a linear-like food chain, with a large proportion of specialized organisms, including dolphins, shearwaters, and large pelagic fish. The low mean trophic level of the system was 2.03, much lower than that of fisheries (4.3) targeting mainly tunas and Black scabbardfish. Considering the importance of marine megafauna in this food web and the threats they are facing; monitoring studies of key species in the region should be a priority. This study can now be used to build a needed ecosystem-based fisheries management and integrate conservation measures to declining species.
•Lower trophic level organisms comprise 89.9 % of Madeira's marine biomass.•Sharks, coastal birds, and monk seals are the keystone species of this food web.•Marine megafauna have the highest overall average Mixed Trophic Impact on the food web.•The ecosystem has a reduced resilience due to the high number of specialists.•High-trophic level fisheries require management reassessment.
Declines in European bird populations are reported for decades but the direct effect of major anthropogenic pressures on such declines remains unquantified. Causal relationships between pressures and ...bird population responses are difficult to identify as pressures interact at different spatial scales and responses vary among species. Here, we uncover direct relationships between population time-series of 170 common bird species, monitored at more than 20,000 sites in 28 European countries, over 37 y, and four widespread anthropogenic pressures: agricultural intensification, change in forest cover, urbanisation and temperature change over the last decades. We quantify the influence of each pressure on population time-series and its importance relative to other pressures, and we identify traits of most affected species. We find that agricultural intensification, in particular pesticides and fertiliser use, is the main pressure for most bird population declines, especially for invertebrate feeders. Responses to changes in forest cover, urbanisation and temperature are more species-specific. Specifically, forest cover is associated with a positive effect and growing urbanisation with a negative effect on population dynamics, while temperature change has an effect on the dynamics of a large number of bird populations, the magnitude and direction of which depend on species' thermal preferences. Our results not only confirm the pervasive and strong effects of anthropogenic pressures on common breeding birds, but quantify the relative strength of these effects stressing the urgent need for transformative changes in the way of inhabiting the world in European countries, if bird populations shall have a chance of recovering.
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