Reproductive performance of resident and migrant males, females and pairs in a partially migratory bird

We thank everyone from the Centre for Ecology & Hydrology (CEH) who contributed to data collection, and Scottish Natural Heritage for access to the Isle of May National Nature Reserve. We thank the Scottish Ornithologists’ Club (SOC) for their support, and all volunteer observers, particularly Raymond Duncan, Moray Souter and Bob Swann. HG was funded by a Natural Environment Research Council (NERC) CASE studentship supported by CEH and SOC, FD, SW, MPH, MN and SB were funded by NERC and the Joint Nature Conservation Committee, and JMR was part-funded by the Royal Society. Finally, we thank the Associate Editor and two reviewers for constructive comments on the manuscript. The data are available from the Dryad Digital Repository https://doi.org/10.5061/dryad.532j0 (Grist et al., 2017)Peer reviewedPublisher PD

Validating accelerometry estimates of energy expenditure across behaviours using heart rate data in a free-living seabird

Two main techniques have dominated the field of ecological energetics, the heart-rate and doubly labelled water methods. Although well established, they are not without their weaknesses, namely expense, intrusiveness and lack of temporal resolution. A new technique has been developed using accelerometers; it uses the Overall Dynamic Body Acceleration (ODBA) of an animal as a calibrated proxy for energy expenditure. This method provides high resolution data without the need for surgery. Significant relationships exist between rate of oxygen consumption (V̇o2) and ODBA in controlled conditions across a number of taxa; however, it is not known whether ODBA represents a robust proxy for energy expenditure consistently in all natural behaviours and there have been specific questions over its validity during diving, in diving endotherms. Here we simultaneously deployed accelerometers and heart rate loggers in a wild population of European shags (Phalacrocorax aristotelis). Existing calibration relationships were then used to make behaviour-specific estimates of energy expenditure for each of these two techniques. Compared against heart rate derived estimates the ODBA method predicts energy expenditure well during flight and diving behaviour, but overestimates the cost of resting behaviour. We then combine these two datasets to generate a new calibration relationship between ODBA and V̇o2 that accounts for this by being informed by heart rate derived estimates. Across behaviours we find a good relationship between ODBA and V̇o2. Within individual behaviours we find useable relationships between ODBA and V̇o2 for flight and resting, and a poor relationship during diving. The error associated with these new calibration relationships mostly originates from the previous heart rate calibration rather than the error associated with the ODBA method. The equations provide tools for understanding how energy constrains ecology across the complex behaviour of free-living diving birds

Nest-dwelling ectoparasites reduce begging effort in Pied Flycatcher Ficedula hypoleuca nestlings

Parasitized nestlings might be expected to increase begging effort to obtain additional resources to compensate for those sequestered by their parasites. However, begging is costly and chicks harbouring parasites may find it more difficult to attain high begging levels. Consequently, we predicted that, for the same level of nutritional need, nestlings that are parasitized will invest less in begging than those that are not parasitized. We tested this prediction by measuring begging in Pied Flycatcher Ficedula hypoleuca nestlings parasitized with haematophagous mites Dermanyssus gallinoides and Dermanyssus gallinae and blowfly larvae Protocalliphora azurea, and subjected to different levels of food deprivation in order to control for short-term nutritional need. Nestlings from nests with ectoparasites spent less time begging than those from nests without parasites, especially when very hungry, although there was no association with latency to beg or begging intensity. Our results suggest that time invested in begging may indicate not only the level of need, but also nestling parasitism status.Peer Reviewe

Assessing the vulnerability of the marine bird community in the western North Sea to climate change and other anthropogenic impacts

Ocean warming and anthropogenic activities such as fishing, shipping and marine renewable developments are affecting marine top predators. Research has focussed on the impacts of single stressors on single species, yet understanding cumulative effects of multiple stressors on communities is vital for effective conservation management. We studied a marine bird community (45 species; 11 families) that used the Forth and Tay region of the North Sea for breeding, overwintering or migration between 1980 and 2011. Local sea surface temperature (SST) increased significantly over this period, with concomitant changes in lower trophic levels. Simultaneously, the region has been subject to fishing pressure and shipping disturbance and is a priority area for renewable energy developments. We used colony-based and at-sea data to quantitatively assess relationships between SST and counts, productivity and survival of 25 species for which sufficient data were available for analysis. For the remaining species, we applied a qualitative approach using published population trends, published climate relationships and foraging sensitivity. In total, 53% of species showed negative relationships with SST. Trends in counts and demography were combined with climate vulnerability to give an index of population concern to future climate warming, and 44% of species were classified as high or very high concern, notably cormorants, grebes, skuas, shearwaters, terns and auks, as well as species breeding in the region. Qualitative assessments of vulnerability to fisheries, pollutants, disturbance (including introduced predators), marine renewables and climate found that 93% of species were vulnerable to ≥2 threats, and 58% to ≥4. Our results indicate that the majority of birds in this region of the North Sea face an uncertain future, potentially threatening the resilience of this important marine bird community

Carry-over effects of seasonal migration on reproductive success through breeding site retention in a partially migratory bird.

Acknowledgments We thank everyone who contributed to data collection, most particularly Raymond Duncan, Moray Souter, Adrian Breeman and Doug Grant. Work was supported the University of Aberdeen, UK Centre for Ecology & Hydrology, Royal Society, Norwegian Research Council (project 223257), and a Marie Curie Postdoctoral Fellowship awarded to JM (895904)Peer reviewe

Host-parasite biology in the real world: the field voles of Kielder

Peer reviewedPublisher PD

Sublethal effects of natural parasitism act through maternal, but not paternal; reproductive success in a wild population

Parasites are a major component of all animal populations. Males and females often differ in their levels of parasite prevalence, potentially leading to sex differences in the impact of parasitism on fitness, with important implications for the evolution of parasite and host traits including resistance, tolerance, and virulence. However, quantitative measures of the impact of parasitism under free‐living conditions are extremely rare, as they require detailed host demographic data with measures of parasite burden over time. Here, we use endoscopy for direct quantification of natural‐parasite burdens and relate these to reproductive success over 7 yr in a wild population of seabirds. Contrary to predictions, only female burdens were associated with negative impacts of parasitism on breeding success, despite males having significantly higher burdens. Female reproductive success declined by 30% across the range of natural parasite burdens. These effects persisted when accounting for interannual population differences in breeding success. Our results provide quantitative estimates of profound sub‐lethal effects of parasitism on the population. Importantly, they highlight how parasites act unpredictably to shape ecological and evolutionary processes in different components of the same population, with implications for demography and selection on host and parasite traits

The energetic cost of parasitism in a wild population

Parasites have profound fitness effects on their hosts, yet these are often sub-lethal, making them difficult to understand and quantify. A principal sub-lethal mechanism that reduces fitness is parasite-induced increase in energetic costs of specific behaviours, potentially resulting in changes to time and energy budgets. However, quantifying the influence of parasites on these costs has not been undertaken in free-living animals. We used accelerometers to estimate energy expenditure on flying, diving and resting, in relation to a natural gradient of endo-parasite loads in a wild population of European shags Phalacrocorax aristotelis. We found that flight costs were 10% higher in adult females with higher parasite loads and these individuals spent 44% less time flying than females with lower parasite loads. There was no evidence for an effect of parasite load on daily energy expenditure, suggesting the existence of an energy ceiling, with the increase in cost of flight compensated for by a reduction in flight duration. These behaviour specific costs of parasitism will have knock-on effects on reproductive success, if constraints on foraging behaviour detrimentally affect provisioning of young. The findings emphasize the importance of natural parasite loads in shaping the ecology and life-history of their hosts, which can have significant population level consequences

Parental age influences offspring telomere loss

1. The age of the parents at the time of offspring production can influence offspring longevity, but the underlying mechanisms remain poorly understood. The effect of parental age on offspring telomere dynamics (length and loss rate) is one mechanism that could be important in this context. 2. Parental age might influence the telomere length that offspring inherit or age-related differences in the quality of parental care could influence the rate of offspring telomere loss. However, these routes have generally not been disentangled. 3. Here, we investigated whether parental age was related to offspring telomere dynamics using parents ranging in age from 2 to 22 years old in a free-living population of a long-lived seabird, the European shag (Phalacrocorax aristotelis). By measuring the telomere length of offspring at hatching and towards the end of the post-natal growth period, we could assess whether any potential parental age effect was confined to the post-natal rearing period. 4. There was no effect of maternal or paternal age on the initial telomere length of their chicks. However, chicks produced by older mothers and fathers experienced significantly greater telomere loss during the post-natal nestling growth period. We had relatively few nests in which the ages of both parents were known, and individuals in this population mate assortatively with respect to age. Thus, we could not conclusively determine whether the parental age effect was due to maternal age, paternal age, or both; however, it appears that the effect is stronger in mothers. 5. These results demonstrate that in this species, there was no evidence that parental age was related to offspring hatching telomere length. However, telomere loss during nestling growth was reduced in the offspring of older parents. This could be due to an age-related deterioration in the quality of the environment that parents provide, or because parents that invest less in offspring rearing live to an older age

Interpreting ELISA analyses from wild animal samples: some recurrent issues and solutions

Many studies in disease and ecological immunology rely on the use of assays that quantify the amount of specific antibodies (immunoglobulin) in samples. Enzyme‐linked immunosorbent assays (ELISAs) are increasingly used in ecology due to their availability for a broad array of antigens and the limited amount of sampling material they require. Two recurrent methodological issues are nevertheless faced by researchers: (1) the limited availability of immunological assays and reagents developed for non‐model species, and (2) the statistical determination of the cut‐off threshold used to distinguish individual samples that are likely to have or not to have antibodies against a specific antigen. Here, we outline two solutions to deal with these issues. First, we show that implementing two assays with differing detection methods can help validate the use of reagents, such as antibodies, in species different from their intended target. We illustrate this by comparing the quantification of specific vaccinal antibodies against Newcastle disease virus (NDV) using two ELISA approaches in four seabird species (Cory's shearwater, European shag, European storm petrel and Southern rockhopper penguin). Second, we provide a simple way to determine from the distribution of ELISA values whether the assayed samples are likely to be made of a single group of individuals (likely negative) or of two groups of individuals (negative and positive). We illustrate the use of this approach with two independent datasets: NDV antibody levels following vaccination and anti‐Borrelia antibody levels following natural exposure. The practical implementation of these methodological approaches could provide a way to efficiently apply ELISAs and other immune‐based assays to address questions in the growing fields of ecological immunology and disease ecology