59 research outputs found
Effects of environmental variability and offspring growth on the movement ecology of breeding Scopoli's shearwater Calonectris diomedea
Abstract
Most seabird species display colonial behavior during the breeding period which implies that food resources around breeding sites can easily go depleted. Seabirds need to both reach profitable areas, which can be located far from the colony, and return to the colony regularly. In this context, flexibility in movement behavior may be crucial for breeding success. During chick-rearing, Procellariformes species can alternate short trips lasting 1–4 days for chick provisioning with longer trips for self-provisioning in what has been called a dual-foraging strategy. We analyzed foraging trips from 136 Scopoli's shearwaters from three Mediterranean colonies tracked with GPS during 6 chick-rearing seasons to assess whether the adoption of a dual foraging strategy depends on the quality of habitat surrounding the colony. We found a marked dual-foraging strategy only in birds from the Linosa colony which was the largest colony in terms of breeding pairs and was characterized by having a lower marine habitat quality. Birds from this colony performed foraging trips that extended up to 369 km from the nest and lasted more than 10 days. In general, the decision to perform long lasting trips was triggered by lower values of primary production and higher offspring weight. Contrary to expectation, the decision to feed far from the colony was not related to the parents' weight. At the same time, despite the higher productivity offered by distant areas, the higher proportion of long trips performed by birds breeding in poor areas was not sufficient to maintain the same body mass as the ones breeding in richer areas
Home, dirty home: effect of old nest material on nest-site selection and breeding performance in a cavity-nesting raptor
The quality of a breeding site may have major fitness consequences. A fundamental step to understanding the process of nest-site selection is the identification of the information individuals use to choose high-quality nest sites. For secondary cavity-nesting bird species that do not add nest lining material, organic remains (faeces, pellets) accumulated inside nest cavities during previous breeding events may be a cue for high-quality nest-sites, as they contain information about past successful breeding and may improve thermal insulation of eggs during incubation. However, cavities in which breeding was successful might also contain more nest-dwelling ectoparasites than unoccupied cavities, offering an incentive for prospective parents to avoid them. We exposed breeding cavity-nesting lesser kestrels (Falco naumanni) to nestbox dyads consisting of a dirty (with a thick layer of organic substrate) and a clean nestbox (without organic material). Dirty nestboxes were strongly preferred, being occupied earlier and more frequently than clean ones. Hatching success in dirty nestboxes was significantly higher than in clean ones, suggesting a positive effect of organic nest material on incubation efficiency, while nestbox dirtiness did not significantly affect clutch and brood size. Nestlings from dirty nestboxes had significantly higher ectoparasite load than those from clean nestboxes soon after egg hatching, but this difference was not evident a few days later. Nest substrate did not significantly affect nestling growth. We concluded that nest substrate is a key driver of nest-site choice in lesser kestrels, although the adaptive value of such a strong preference appears elusive and may be context-dependent
Analysis of Movement Recursions to Detect Reproductive Events and Estimate Their Fate in Central Place Foragers
Background
Recursive movement patterns have been used to detect behavioral structure within individual movement trajectories in the context of foraging ecology, home-ranging behavior, and predator avoidance. Some animals exhibit movement recursions to locations that are tied to reproductive functions, including nests and dens; while existing literature recognizes that, no method is currently available to explicitly target different types of revisited locations. Moreover, the temporal persistence of recursive movements to a breeding location can carry information regarding the fate of breeding attempts, but it has never been used as a metric to quantify recursive movement patterns. Here, we introduce a method to locate breeding attempts and estimate their fate from GPS-tracking data of central place foragers. We tested the performance of our method in three bird species differing in breeding ecology (wood stork (Mycteria americana), lesser kestrel (Falco naumanni), Mediterranean gull (Ichthyaetus melanocephalus)) and implemented it in the R package ‘nestR’. Methods
We identified breeding sites based on the analysis of recursive movements within individual tracks. Using trajectories with known breeding attempts, we estimated a set of species-specific criteria for the identification of nest sites, which we further validated using non-reproductive individuals as controls. We then estimated individual nest survival as a binary measure of reproductive fate (success, corresponding to fledging of at least one chick, or failure) from nest-site revisitation histories during breeding attempts, using a Bayesian hierarchical modeling approach that accounted for temporally variable revisitation patterns, probability of visit detection, and missing data. Results
Across the three species, positive predictive value of the nest-site detection algorithm varied between 87 and 100% and sensitivity between 88 and 92%, and we correctly estimated the fate of 86–100% breeding attempts. Conclusions
By providing a method to formally distinguish among revisited locations that serve different ecological functions and introducing a probabilistic framework to quantify temporal persistence of movement recursions, we demonstrated how the analysis of recursive movement patterns can be applied to estimate reproduction in central place foragers. Beyond avian species, the principles of our method can be applied to other central place foraging breeders such as denning mammals. Our method estimates a component of individual fitness from movement data and will help bridge the gap between movement behavior, environmental factors, and their fitness consequences
Scalable software framework for real-time data processing in the railway environment
Background: Ticks are obligate haematophagous ectoparasites of vertebrates and frequently parasitize avian species that can carry them across continents during their long-distance migrations. Ticks may have detrimental effects on the health state of their avian hosts, which can be either directly caused by blood-draining or mediated by microbial pathogens transmitted during the blood meal. Indeed, ticks host complex microbial communities, including bacterial pathogens and symbionts. Midichloria bacteria (Rickettsiales) are widespread tick endosymbionts that can be transmitted to vertebrate hosts during the tick bite, inducing an antibody response. Their actual role as infectious/pathogenic agents is, however, unclear. Methods: We screened for Midichloria DNA African ticks and blood samples collected from trans-Saharan migratory songbirds at their arrival in Europe during spring migration. Results: Tick infestation rate was 5.7%, with most ticks belonging to the Hyalomma marginatum species complex. Over 90% of Hyalomma ticks harboured DNA of Midichloria bacteria belonging to the monophylum associated with ticks. Midichloria DNA was detected in 43% of blood samples of avian hosts. Tick-infested adult birds were significantly more likely to test positive to the presence of Midichloria DNA than non-infested adults and second-year individuals, suggesting a long-term persistence of these bacteria within avian hosts. Tick parasitism was associated with a significantly delayed timing of spring migration of avian hosts but had no significant effects on body condition, whereas blood Midichloria DNA presence negatively affected fat deposits of tick-infested avian hosts. Conclusions: Our results show that ticks effectively transfer Midichloria bacteria to avian hosts, supporting the hypothesis that they are infectious to vertebrates. Bird infection likely enhances the horizontal spread of these bacteria across haematophagous ectoparasite populations. Moreover, we showed that Midichloria and tick parasitism have detrimental non-independent effects on avian host health during migration, highlighting the complexity of interactions involving ticks, their vertebrate hosts, and tick-borne bacteria
Year-round variation in the isotopic niche of Scopoli's shearwater (Calonectris diomedea) breeding in contrasting sea regions of the Mediterranean Sea
Top marine predators are key components of marine food webs. Among them, long-distance migratory seabirds,
which travel across different marine ecosystems over the year, may experience important year-round changes in
terms of oceanographic conditions and availability of trophic resources. We tested whether this was the case in
the Scopoli’s shearwater (Calonectris diomedea), a trans-equatorial migrant and top predator, by sampling birds
breeding in three environmentally different regions of the Mediterranean Sea. The analysis of positional data and
stable isotopes (δ13
C and δ15N) of target feathers revealed that birds from the three regions were spatially
segregated during the breeding period while they shared non-breeding areas in the Atlantic Ocean. Isotopic
baseline levels of N and C (meso-zooplankton) were significantly different among marine regions during
breeding. Such variation was reflected at the higher trophic levels of pelagic and demersal fish muscles as well as
in shearwater feathers grown in the Mediterranean. δ15N- and δ13C-adjusted values of shearwaters were significantly different among populations suggesting that birds from different breeding areas relied on prey species
from different trophic levels. Conversely, the non-breeding spatial and isotopic niches overlapped greatly among
the three populations. Shearwater trophic niches during breeding were narrower and segregated compared to the
non-breeding period, revealing a high plasticity in trophic resource use. Overall, this study highlights seasonal
and region-specific use of trophic resources by Scopoli’s shearwater, suggesting a broad trophic plasticity and
possibly a high adaptability to environmental changes.Fundação para a Ciência e Tecnologia - FCTinfo:eu-repo/semantics/publishedVersio
Context-dependent foraging habitat selection in a farmland raptor along an agricultural intensification gradient
Gradients of agricultural intensification in agroecosystems may determine uneven resource availability for
predators relying on these man-made habitats. In turn, these variations in resource availability may affect
predators’ habitat selection patterns, resulting in context-dependent habitat selection. We assessed the effects of
gradients of landscape composition and configuration on habitat selection of a colonial farmland bird of prey, the
lesser kestrel (Falco naumanni), relying on 76 GPS-tracked nestling-rearing individuals from 10 populations
scattered along an agricultural intensification gradient. Analyses were conducted considering two ecological
levels of aggregation (the population and the individual) and two spatial scales of habitat availability (the colony
surroundings and the individual home-range). Overall, non-irrigated croplands and semi-natural grasslands were
the most preferred habitats at both spatial scales. At the colony scale, lesser kestrels showed a preference for
grassland compared to non-irrigated crops, whereas the opposite was the case within individual home-ranges.
Conversely, croplands were positively selected with comparable intensity at both spatial scales. Strong selection
for grassland at the colony scale highlights the importance of this semi-natural habitat for the species. The
weaker preference for grassland at the home-range scale is likely due to the phenology and structure of the
vegetation in the late breeding season. Spatial scale differences in selection patterns may thus derive from spatiotemporal
changes in resource availability through the breeding season. The strength of selection for the two most
used habitats varied markedly among individuals. At the spatial scale of the colony, individual selection strength
for grasslands increased with decreasing compositional diversity of the surrounding landscape, suggesting that
agroecosystem heterogeneity may at least partly buffer the loss of semi-natural habitats. At the within homerange
scale, higher cropland availability reduced the strength of individual preference for this habitat, suggesting
a negative functional response possibly related to density-dependent processes acting on foraging
movements. Our study provides evidence that farmland species show context-dependent habitat selection patterns
in response to landscape gradients shaped by agricultural intensification as well as by intrinsic characteristics
and habitat availability. Our findings highlight the importance of addressing both individual and
population-level variability and considering multiple spatial scales in studies of habitat selection to inform
species’ management and conservation
Birds of a feather flock together:a dataset for Clock and Adcyap1 genes from migration genetics studies
Birds in seasonal habitats rely on intricate strategies for optimal timing of migrations. This is governed by environmental cues, including photoperiod. Genetic factors affecting intrinsic timekeeping mechanisms, such as circadian clock genes, have been explored, yielding inconsistent findings with potential lineage-dependency. To clarify this evidence, a systematic review and phylogenetic reanalysis was done. This descriptor outlines the methodology for sourcing, screening, and processing relevant literature and data. PRISMA guidelines were followed, ultimately including 66 studies, with 34 focusing on candidate genes at the genotype-phenotype interface. Studies were clustered using bibliographic coupling and citation network analysis, alongside scientometric analyses by publication year and location. Data was retrieved for allele data from databases, article supplements, and direct author communications. The dataset, version 1.0.2, encompasses data from 52 species, with 46 species for the Clock gene and 43 for the Adcyap1 gene. This dataset, featuring data from over 8000 birds, constitutes the most extensive cross-species collection for these candidate genes, used in studies investigating gene polymorphisms and seasonal bird migration.</p
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
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