Vitor H. Paiva

Bio: Vitor H. Paiva is an academic researcher from University of Coimbra. The author has contributed to research in topics: Foraging & Seabird. The author has an hindex of 24, co-authored 100 publications receiving 1662 citations. Previous affiliations of Vitor H. Paiva include Life Sciences Institute & University of Kiel.

Foraging plasticity in a pelagic seabird species along a marine productivity gradient

Abstract: The foraging plasticity in a pelagic seabird species, Cory's shearwater Calonectris diomedea, was compared during incubation and chick-rearing among 7 different breeding sites in the North Atlantic. These sites, with contrasting ecological conditions, were situated in the Azores (Corvo, Faial, Graciosa and Sta. Maria), Berlengas (Berlenga), Madeira (Desertas) and Selvagens (Selvagem Grande) archipelagos. Behavioural data were obtained by intensively deploying compass- temperature and temperature-depth data loggers, monitoring 302 and 22 foraging excursions, respectively. A principal component analysis revealed 2 main groups, one foraging along a neritic shelf (Berlengas population) and the other foraging in pelagic oceanic areas (populations from Azores, Madeira and Selvagens). There was a significant positive correlation (rS = 0.55) between the percentage of short foraging trips in the different breeding sites and the concentration of chlorophyll-a in the waters surrounding those sites. Birds exploiting neritic areas used shallower depths (4.9 ± 2.3 m) and shorter dives (17.0 ± 2.2 s) than birds feeding in oceanic waters (9.8 ± 2.4 m and 32.0 ± 5.8 s respectively). This indicates that birds adapted their modes of predation to cope with the diverse dis- tribution of their prey items. Overall, the behavioural response of the different populations was mainly dictated by the heterogeneity of their habitat, which was driven by 2 productivity gradients present in the north Atlantic. (1) Productivity is expected to increase from the subtropical warmer waters close to Selvagens to northern colder waters north of the Azores archipelago. (2) Oceanic environments are expected to be less profitable than coastal areas (upwelling areas), such as the Portuguese and African coasts.

Oceanographic characteristics of areas used by Cory's shearwaters during short and long foraging trips in the North Atlantic

Abstract: Many breeding seabird species are central-place foragers and constrained to find productive prey patches within their foraging ranges. We assessed how different populations of a pelagic seabird species, the Cory’s shearwater Calonectris diomedea, breeding in oceanic and neritic conditions, cope with these constraints in the North Atlantic, during both incubation and chick-rearing periods. We analysed 237 foraging trips to study the movements and oceanographic characteristics of foraging habitats of seven different populations of Cory’s shearwaters. Generally, oceanic populations exhibited higher foraging effort, by travelling more time and to more distant areas, and larger home ranges and feeding areas, than the neritic population (i.e. breeding on an island within the Portuguese continental platform). On their short trips (i.e. ≤4 days), birds from the different populations fed mostly in shallower waters around the colony. During long trips (i.e. ≥5 days), feeding areas of both oceanic and neritic populations were characterized by high concentration values of chlorophyll-a, low sea-surface temperature and shallower habitats, with oceanic populations of the Azores exploiting areas north of the islands over known seamounts and frontal regions. Birds from other oceanic population (Selvagens) also exploited the African continental shelf system on their long trips. The home ranges of the different populations overlapped widely, but there was a general spatial segregation in terms of the core feeding areas at the population level. Core feeding areas and areas of foraging overlap between different populations should be important to inform conservation management measures, such as the definition of Marine Important Bird Areas for seabirds over the North Atlantic.

How area restricted search of a pelagic seabird changes while performing a dual foraging strategy

Abstract: Movements and foraging strategies of marine predators should cope with the hierarchical spatial distribution of resources. Therefore, in order to predict the at-sea distribution of aerial predators, it is crucial to understand the factors governing trajectory decisions at different scales. Using first passage time (FPT) analysis on precision tracking information (GPS-loggers data) we were able to examine the foraging strategy of Cory's shearwaters Calonectris diomedea and to detect the adoption of area-restricted search (ARS), measuring the scale and duration of this behaviour. Data were collected from three different populations foraging in different oceanographic conditions. During long excursions birds only commuted between their colony and prey patches, while on their short movements birds increased the amount of looping movements. On short trips, birds addopted ARS behaviour at an average scale of 18 km and at a second nested scale of around 2 km. When engaging in long trips, first scale of ARS occurred on average at about 67 km of radii and than a second nested scale at a radii of 24 km. Overall, the different populations showed foraging patterns matching the habitats exploited: a) at smaller scales of ARS, sea-surface temperature, chlorophyll-a concentration and depth influenced the time of residence (i.e. FPT) of birds (with variations at a population level); b) at larger scales of ARS, FPT increased within regions of higher gradients of sea-surface temperature, chlorophyl-a concentration and depth. This study demonstrates that Cory's shearwaters adopt scale-dependent adjustments of movement in relation to the hierarchical distribution of the environment they exploit, matching the scale and duration of ARS with the hierarchical distribution of the environmental features.

Annual and seasonal consistency in the feeding ecology of an opportunistic species, the yellow-legged gull Larus michahellis

Abstract: This study investigated the extent to which the plasticity of a generalist, opportunistic species allows individuals to shift their feeding ecology and foraging niche, throughout the annual cycle, and between 2 years of contrasting diet and oceanographic conditions during the breeding season. The spatio-temporal variations in the foraging niche of an overpopulated gull species-the yellow-legged gull Larus michahellis population at Berlenga Island (Portugal)-were assessed using blood (plasma and cells) and different feathers for stable isotope analyses (delta C-13 and delta N-15) from 52 breeding adults in 2 consecutive years (2011 and 2012). In addition, GPS loggers were deployed on 11 individuals (and removed after several foraging trips) to infer the foraging behaviour of this species during the incubation period. Results suggest inter-annual differences in the feeding ecology and foraging behaviour of birds during the breeding season that were associated with the availability of food resources around the colony. Despite the high feeding plasticity and opportunistic behaviour of yellow-legged gulls, individual birds exhibited short-and long-term consistency in their feeding ecology, with exception of the period between winter and pre-laying. Our results support the hypothesis that individual feeding preferences throughout most of the annual cycle are an intrinsic characteristic of this population, and potentially of related opportunistic and generalist species.

Effects of environmental variability on different trophic levels of the North Atlantic food web

Abstract: The effects of environmental change on the biodiversity, structure and functioning of marine ecosystems is still poorly understood. In fact, very few studies have focused on changes in the at-sea foraging tactics of pelagic seabirds in relation to environmental stochasticity. Aiming at filling this knowledge gap, from 2005 to 2010 we directly measured the influence of climate (as driven by the North Atlantic Oscillation phenomenon) on (1) marine productivity (i.e. chlorophyll a concentration), (2) fish prey abundances and (3) the foraging behaviour of a top marine predator, the Cory's shearwater Calonectris diomedea borealis. There was a dramatic change in the forag- ing strategy of the birds during 2010, which seems to be mostly related to a climatic event that occurred during the winter of 2009 to 2010. This event had a negative impact on the productivity of the surroundings of the breeding colony and decreased the abundance of pelagic prey fish, which in turn altered the spatial, feeding and trophic ecology of Cory's shearwater and decreased their reproductive success. However, the negative trend in the abundance of pelagic prey (esti- mated from acoustic surveys and commercial fisheries landings) may be of concern because it does not seem to be only related to the climatic event of 2010. Long-term monitoring of the inter- actions between top predators, their prey and lower strata of the food web is crucial for a compre- hensive assessment of the impacts that environmental variation may have on coastal ecosystems worldwide.

Influence of Diet On the Distribtion of Nitrogen Isotopes in Animals

Abstract: The influence of diet on the distribution of nitrogen isotopes in animals was investigated by analyzing animals grown in the laboratory on diets of constant nitrogen isotopic composition. The isotopic composition of the nitrogen in an animal reflects the nitrogen isotopic composition of its diet. The δ^(15)N values of the whole bodies of animals are usually more positive than those of their diets. Different individuals of a species raised on the same diet can have significantly different δ^(15)N values. The variability of the relationship between the δ^(15)N values of animals and their diets is greater for different species raised on the same diet than for the same species raised on different diets. Different tissues of mice are also enriched in ^(15)N relative to the diet, with the difference between the δ^(15)N values of a tissue and the diet depending on both the kind of tissue and the diet involved. The δ^(15)N values of collagen and chitin, biochemical components that are often preserved in fossil animal remains, are also related to the δ^(15)N value of the diet. The dependence of the δ^(15)N values of whole animals and their tissues and biochemical components on the δ^(15)N value of diet indicates that the isotopic composition of animal nitrogen can be used to obtain information about an animal's diet if its potential food sources had different δ^(15)N values. The nitrogen isotopic method of dietary analysis probably can be used to estimate the relative use of legumes vs non-legumes or of aquatic vs terrestrial organisms as food sources for extant and fossil animals. However, the method probably will not be applicable in those modern ecosystems in which the use of chemical fertilizers has influenced the distribution of nitrogen isotopes in food sources. The isotopic method of dietary analysis was used to reconstruct changes in the diet of the human population that occupied the Tehuacan Valley of Mexico over a 7000 yr span. Variations in the δ^(15)C and δ^(15)N values of bone collagen suggest that C_4 and/or CAM plants (presumably mostly corn) and legumes (presumably mostly beans) were introduced into the diet much earlier than suggested by conventional archaeological analysis.

Marine defaunation: Animal loss in the global ocean

Abstract: BACKGROUND: Comparing patterns of ter- restrial and marine defaunation helps to place human impacts on marine fauna in context and to navigate toward recovery. De- faunation began in ear- nest tens of thousands of years later in the oceans than it did on land. Al- though defaunation has been less severe in the oceans than on land, our effects on marine animals are increasing in pace and impact. Humans have caused few complete extinctions in the sea, but we are responsible for many ecological, commercial, and local extinctions. Despite our late start, humans have already powerfully changed virtually all major marine ecosystems. ADVANCES: Humans have profoundly de- creased the abundance of both large (e.g., whales) and small (e.g., anchovies) marine fauna. Such declines can generate waves of ecological change that travel both up and down marine food webs and can alter ocean ecosystem functioning. Human harvesters have also been a major force of evolutionary change in the oceans and have reshaped the genetic structure of marine animal popula- tions. Climate change threatens toaccelerate marine defaunation over the next century. The high mobility of many marine animals offers some increased, though limited, ca- pacity for marine species to respond to cli- mate stress, but it also exposes many species to increased risk from other stressors. Be- cause humans are intensely reliant on ocean ecosystems for food and other ecosystem ser- vices, we are deeply affected by all of these forecasted changes. Three lessons emerge when comparing the marine and terrestrial defaunation ex-