Estimates of avian collision with power lines and carcass disappearance across differing environments

Data on collisions of birds with high-voltage electric power lines are scarce and are often gathered without protocols for the correction of carcass disappearance. There is actually growing awareness that it is important to accomplish carcass removal trials in order to develop correction factors for producing adjusted estimates of mortality due to collisions. In this study, we provided for the first time raw counts and estimates of bird collisions across seven Italian areas that largely differ in their habitats. We also carried out carcass removal trials to compute the rate of carcass disappearance and produce better estimates of collision events and of optimal time intervals of carcass searches. Results of 1-year monitoring showed a general low frequency of birds collided with the power lines. Carcass removal trials showed effects of carcass size and season on the carcass disappearance, which varied largely among the study areas. In four areas, both small and large carcasses had more than 50% probability to be removed within 3–5 days from their distribution. Given the high variation among study areas, we suggest that estimates of carcass persistence and optimal time intervals should be conducted concurrently for each new study site

Using the BirdTree.org website to obtain robust phylogenies for avian comparative studies: A primer

Comparative studies of trait evolution require accounting for the shared evolutionary history. This is done by including phylogenetic hypotheses into statistical analyses of species’ traits, for which birds often serve as excellent models. The online publication of the most complete molecular phylogeny of extant bird species (www.birdtree.org, BirdTree hereafter) now allows evolutionary biologists to rapidly obtain sets of equally plausible phylogenetic trees for any set of species to be incorporated as a phylogenetic hypothesis in comparative analyses. We discuss methods to use BirdTree tree sets for comparative studies, either by building a consensus tree that can be incorporated into standard comparative analyses, or by using tree sets to account for the effect of phylogenetic uncertainty. Methods accounting for phylogenetic uncertainty should be preferred whenever possible because they should provide more reliable parameter estimates and realistic confidence intervals around them. Based on a real comparative dataset, we ran simulations to investigate the effect of variation in the size of the random tree sets downloaded from BirdTree on the variability of parameter estimates from a bivariate relationship between mass-specific productivity and body mass. Irrespective of the method of analysis, using at least 1,000 trees allows obtaining parameter estimates with very small (< 0.15%) coefficients of variation. We argue that BirdTree, due to the ease of use and the major advantages over previous ‘traditional’ methods to obtain phylogenetic hypotheses of bird species (e.g. supertrees or manual coding of published phylogenies), will become the standard reference in avian comparative studies for years to comePeer reviewe

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

Quantifying the robustness of first arrival dates as a measure of avian migratory phenology

As the climate changes, many long-term studies have shown that the timing of bird migration is shifting, increasing the need for reliable measures of migratory phenology. Ideally, daily counts of birds at a site are used to calculate the mean arrival date (MAD) but, as this approach is not always possible and is very labour-intensive, simpler metrics such as first arrival date (FAD) have commonly been used. Here, we examine the relationship between FAD and MAD in 28 summer migrant bird species over a 42-year period (1970–2011) at Portland Bird Observatory, UK. Although significant correlations between FAD and MAD were detected, relationships were weak, particularly in long-distance migrants. We suggest that FAD, although a simple and straightforward measure, is not particularly robust as a proxy for overall migratory phenology at a population level

Challenging claims in the study of migratory birds and climate change

Recent shifts in phenology in response to climate change are well established but often poorly understood. Many animals integrate climate change across a spatially and temporally dispersed annual life cycle, and effects are modulated by ecological interactions, evolutionary change and endogenous control mechanisms. Here we assess and discuss key statements emerging from the rapidly developing study of changing spring phenology in migratory birds. These well-studied organisms have been instrumental for understanding climate-change effects, but research is developing rapidly and there is a need to attack the big issues rather than risking affirmative science. Although we agree poorly on the support for most claims, agreement regarding the knowledge basis enables consensus regarding broad patterns and likely causes. Empirical data needed for disentangling mechanisms are still scarce, and consequences at a population level and on community composition remain unclear. With increasing knowledge, the overall support (‘consensus view’) for a claim increased and between-researcher variability in support (‘expert opinions') decreased, indicating the importance of assessing and communicating the knowledge basis. A proper integration across biological disciplines seems essential for the field's transition from affirming patterns to understanding mechanisms and making robust predictions regarding future consequences of shifting phenologies

No short-term effects of geolocators on flight performance of an aerial insectivorous bird, the Barn Swallow (Hirundo rustica)

Miniaturized light-level geolocators are becoming increasingly popular devices for the study of avian migration. However, the effects of these devices on birds' flight behaviour, and hence fitness components, are poorly known. We investigated the effect of miniaturized geolocators on flight performance of the Barn Swallow (Hirundo rustica), which may be especially susceptible to geolocator deployment as it is a small (~20 g), aerially insectivorous, long-distance migratory species. We tested whether miniaturized geolocators (~3.5 % of body mass) affected short-term flight performance traits of breeding males by comparing flight manoeuvrability, velocity and acceleration of geolocator-equipped versus control (handled only) birds in flight tunnels. We used a robust experimental design wherein the within-individual change in flight performance was compared between geolocator-equipped birds (after allowing for a period of acclimation) and control birds (that were also tested twice). We found no statistically significant evidence that short-term flight performance traits were affected by geolocator deployment. Here we discuss the implications of our findings for the deployment of geolocators in studies of migratory behaviour of small birds

Extra food provisioning does not affect behavioral lateralization in nestling lesser kestrels

Costs and benefits of brain lateralization may depend on environmental conditions. Growing evidence indicates that the development of brain functional asymmetries is adaptively shaped by the environmental conditions experienced during early life. Food availability early in life could act as a proxy of the environmental conditions encountered during adulthood, but its potential modulatory effect on lateralization has received little attention. We increased food supply from egg laying to early nestling rearing in a wild population of lesser kestrels Falco naumanni, a sexually dimorphic raptor, and quantified the lateralization of preening behavior (head turning direction). As more lateralized individuals may perform better in highly competitive contexts, we expected that extra food provisioning, by reducing the level of intra-brood competition for food, would reduce the strength of lateralization. We found that extra food provisioning improved nestling growth, but it did not significantly affect the strength or direction of nestling lateralization. In addition, maternal body condition did not explain variation in nestling lateralization. Independently of extra food provisioning, the direction of lateralization differed between the sexes, with female nestlings turning more often toward their right. Our findings indicate that early food availability does not modulate behavioral lateralization in a motor task, suggesting limited phenotypic plasticity in this trait

Plasma markers of oxidative stress are uncorrelated in a wild mammal.

This is the final version of the article. Available from Wiley via the DOI in this record.Oxidative stress, which results from an imbalance between the production of potentially damaging reactive oxygen species versus antioxidant defenses and repair mechanisms, has been proposed as an important mediator of life-history trade-offs. A plethora of biomarkers associated with oxidative stress exist, but few ecological studies have examined the relationships among different markers in organisms experiencing natural conditions or tested whether those relationships are stable across different environments and demographic groups. It is therefore not clear to what extent studies of different markers can be compared, or whether studies that focus on a single marker can draw general conclusions regarding oxidative stress. We measured widely used markers of oxidative damage (protein carbonyls and malondialdehyde) and antioxidant defense (superoxide dismutase and total antioxidant capacity) from 706 plasma samples collected over a 4-year period in a wild population of Soay sheep on St Kilda. We quantified the correlation structure among these four markers across the entire sample set and also within separate years, age groups (lambs and adults), and sexes. We found some moderately strong correlations between some pairs of markers when data from all 4 years were pooled. However, these correlations were caused by considerable among-year variation in mean marker values; correlation coefficients were small and not significantly different from zero after accounting for among-year variation. Furthermore, within each year, age, and sex subgroup, the pairwise correlation coefficients among the four markers were weak, nonsignificant, and distributed around zero. In addition, principal component analysis confirmed that the four markers represented four independent axes of variation. Our results suggest that plasma markers of oxidative stress may vary dramatically among years, presumably due to environmental conditions, and that this variation can induce population-level correlations among markers even in the absence of any correlations within contemporaneous subgroups. The absence of any consistent correlations within years or demographic subgroups implies that care must be taken when generalizing from observed relationships with oxidative stress markers, as each marker may reflect different and potentially uncoupled biochemical processes.We would like to thank Melissa M. Page, Ruth Banks, Christopher Mitchell and Sharon Mitchell for technical assistance and the St Kilda summer field teams of 2010-2013. In addition, we are very grateful to the National Trust for Scotland for permission to carry out fieldwork on St Kilda, and QinetiQ, Angus Campbell and Kilda Cruises for logistic support. LLC was supported by a BBSRC EASTBIO Doctoral Training Partnership Studentship and DHN by a BBSRC David Phillips Fellowship. The Soay sheep project was supported by a NERC responsive mode grant to JMP over the course of our four-year study

Perinatal variation and covariation of oxidative status and telomere length in yellow-legged gull chicks.

The perinatal period is critical to survival and performance of many organisms. In birds, rapid postnatal growth and sudden exposure to aerial oxygen around hatching markedly affect the chick redox status, with potentially negative consequences on physiology mediated by oxidative stress. In addition, telomere length (TL) undergoes reduction during birds' early life, partly depending on oxidative status. However, relatively few studies have focused specifically on the changes in oxidative status and TL that occur immediately after hatching. In this study of the yellow-legged gull Larus michahellis, we found that chicks undergo a marked increase in plasma total antioxidant capacity and a marked decrease in the concentration of pro-oxidant molecules during the first days after hatching. In addition, TL in erythrocytes decreased by 1 standard deviation over the 4 days post-hatching. Body mass and tarsus length covaried with total antioxidant capacity and concentration of pro-oxidants in a complex way, that partly depended on sex and laying order, suggesting that oxidative status can affect growth. Moreover, TL positively covaried with the concentration of pro-oxidant molecules, possibly because retention of high concentrations of pro-oxidant molecules results from mechanisms of prevention of their negative effects, including reduction in TL. Thus, this study shows that chicks undergo marked variation in oxidative status, which predicts growth and subsequent TL, prompting for more studies of the perinatal changes in the critical post-hatching stages