Publications for Saskia Wischnewski

What is our power to detect device effects in animal tracking studies?

The use of bio-logging devices to track animal movement continues to grow as technological advances and device miniaturisation allow researchers to study animal behaviour in unprecedented detail. Balanced against the remarkable data that bio-loggers can provide is a need to understand the impact of devices on animal behaviour and welfare.

Recent meta-analyses have demonstrated the impacts of device attachment on animal behaviour, but there is a concern about the frequency and clarity with which device effects are reported. One aspect lacking in many studies is assessment of the statistical power of tests of device effects, yet such information would assist the interpretation of results. We address this issue by providing an overview of the statistical power, as well as the Type M (magnitude) and Type S (sign) error rate, of tests of device effects within the avian tracking literature across a range of assumed effect sizes.

The median power of statistical tests ranged from 9% to 65% across a range of assumed effect sizes corresponding to benchmark values for small, moderate and large effects (d = 0.2, 0.5, 0.8, respectively). Moreover, when using effect sizes derived from previous a meta-analysis (d = 0.1), median power was only 6%. When assuming smaller effect sizes, statistical tests were characterised by high Type M and Type S error rates, suggesting that statistically significant results of device effects will tend to exaggerate the size of such effects and may estimate the sign of an effect in the wrong direction.

Well-designed tracking studies will reduce device effects to low levels and consequently issues associated with low power will be commonplace. Nevertheless, assessment of device effects remains important, particularly when embarking on novel tracking studies. We recommend that statistical tests of device effects are reported clearly and are routinely accompanied by assessment of statistical power, including Type M and Type S errors, based upon realistic external estimates of effect size. Reporting the statistical power can help avoid the pitfalls of overstating results from individual studies, shift the emphasis to accurate reporting of effect sizes and guide decisions about the ethical impacts of device attachment.

Date
25 March 2021
RSPB Authors
Ian Cleasby, Dr Mark Bolton, Dr Ellie Owen, Linda Wilson, Saskia Wischnewski
Authors
Cleasby, Ian R Morrissey, Barbara J Bolton, Mark Owen, Ellie Wilson, Linda Wischnewski, Saskia Nakagawa, Shinichi
Published in
Methods in Ecology and Evolution
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Feasibility study of large-scale deployment of colour-ringing on Black-legged Kittiwake populations to improve the realism of demographic models assessing the population impacts of offshore wind farms

Renewable energy developments, including offshore wind-farms, have been identified as a key component in international efforts to mitigate climate change and its impact on biodiversity. This has led to an increasing number of offshore wind-farms around the UK, however these can have negative impacts on seabird populations. Population Viability Analysis (PVA) is frequently used to quantify these potential negative effects on seabird populations and is a vital part of the consenting process.

However, a lack of empirical data on many aspects of seabird demography means that there can be considerable uncertainty in these assessments. Black-legged Kittiwake Rissa tridactyla populations are thought to be particularly sensitive to additional mortality caused by collision with offshore wind turbines and are often highlighted as a feature of Special Protection Areas (SPAs). Offshore wind-farms, therefore, have been identified as potentially causing an adverse effect on site integrity at some SPAs. Despite being a relatively well-studied species, there is still much uncertainty in our knowledge of Kittiwake demographic rates and meta-population dynamics, which impedes our ability to accurately assess the way populations might respond to additional wind farm-induced mortality.

The Offshore Wind Strategic Monitoring and Research Forum (OWSMRF) identified a large-scale colour-ringing programme of Kittiwake colonies across the UK as one potential approach for improving empirical estimates of Kittiwake demographic rates. Therefore, the main aim of this project was to determine the extent to which colour-ringing can be used to obtain reliable baseline estimates of key demographic rates in Kittiwake populations to improve the realism of demographic models assessing the population impacts of offshore wind farms, and thereby reduce uncertainty around these predicted impacts.

Date
01 February 2021
RSPB Authors
Saskia Wischnewski
Authors
O’Hanlon, NJ Wischnewski, S Ewing, D Newman, K Gunn, C Jones, EL Newell, M Butler, A Quintin, M Searle, K
Published in
JNCC Report
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An investigation of the effects of GPS tagging on the behaviour of black-legged kittiwakes Rissa tridactyla

The deployment of animal-borne tracking devices has revolutionised the study of animal behaviour, providing the opportunity to understand aspects of animal movement, physiology and ecology that were previously difficult to study. Such advances have been particularly important in the study of seabirds where the introduction of GPS tagging has allowed researchers to track the movement and behaviour of individuals while they are at sea. However, it is widely recognized that the negative effects associated with tag instrumentation on animal behaviour cannot be completely avoided and needed to be considered when using tracking data. For example, tagging an individual may lead to changes in its behaviour causing it to act atypically, which casts doubt upon any biological interpretation that arises from such data. In order to design studies in which the effect of tagging on behaviour is minimized researchers have typically sought to use the lightest tags available. Researchers have often used one of two commonly encountered rules-of-thumb that 1) a tag should not exceed 5% of the body mass of the tagged animal; or 2) a tag should not exceed 3% of the body mass of the tagged animal. However, there is little evidence supporting these general rules and it has been recommended that tagging studies provide some empirical examination of the potential effects of tagging when possible.

Here, we investigate the effect of GPS-tagging on the behaviour of black-legged kittiwakes, Rissa tridactyla, that were tagged during the breeding season across multiple UK colonies in the North Sea as part of the RSPB FAME / STAR tracking project.

Date
12 October 2020
RSPB Authors
Dr Aly McCluskie, Dr Ellie Owen, Saskia Wischnewski, Linda Wilson, Dr Lucy Wright, Dr Mark Bolton
Published in
RSPB Technical Report
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Spatio-temporal patterns of foraging behaviour in a wide-ranging seabird reveal the role of primary productivity in locating prey

Predicting the distribution and behaviour of animals is a fundamental objective in ecology and a cornerstone of conservation biology. Modelling the distribution of ocean-faring species like seabirds remains a significant challenge due to ocean dynamics, colony-specific effects and the vast ranges seabirds can cover. We used a spatial and behavioural approach to model the distribution of the Manx shearwater Puffinus puffinus, a pelagic, central-place forager that can cover great distances while foraging. GPS data from birds tagged in 2 colonies over 3 yr were modelled with a range of environmental predictors of marine productivity. For both colonies, transitions to foraging behaviour correlated with chlorophyll a, and the distribution of foraging behaviour was also associated with areas of high chlorophyll a concentration in coastal but not offshore areas for one colony. Furthermore, there was evidence for colony differences in habitat use, prevalence of nocturnal foraging, and for some competitive exclusion on foraging grounds, even though the colonies were 170 km apart. Despite the extensive dataset, our models had modest predictive power, which we suggest can probably only be improved by including biotic interactions, including more direct measures of food resource distribution. Our results highlight the importance of including spatial complexity and data from multiple sites when predicting the distribution of wide-ranging predators, because patterns of distribution and habitat use likely differ across the range of a population.

Date
30 July 2020
RSPB Authors
Saskia Wischnewski
Authors
Kane, Adam Pirotta, Enrico Wischnewski, Saskia Critchley, Emma Jane Bennison, Ashley Jessopp, Mark Quinn, John L
Published in
Marine Ecology Progress Series
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Acoustic activity across a seabird colony reflects patterns of within‐colony flight rather than nest density

Passive acoustic monitoring is increasingly being used as a cost-effective way to study wildlife populations, especially those that are difficult to census using conventional methods. Burrow-nesting seabirds are among the most threatened birds globally, but they are also one of the most challenging taxa to census, making them prime candidates for research into such automated monitoring platforms. Passive acoustic monitoring has the potential to determine presence/absence or quantify burrow-nesting populations, but its effectiveness remains unclear. We compared passive acoustic monitoring, tape-playbacks and GPS tracking data to investigate the ability of passive acoustic monitoring to capture unbiased estimates of within-colony variation in nest density for the Manx Shearwater Puffinus puffinus. Variation in acoustic activity across 12 study plots on an island colony was examined in relation to burrow density and environmental factors across 2 years. As predicted fewer calls were recorded when wind speed was high, and on moon-lit nights, but there was no correlation between acoustic activity and the density of breeding birds within the plots as determined by tape-playback surveys. Instead, acoustic indices correlated positively with spatial variation in the in-colony flight activity of breeding individuals detected by GPS. Although passive acoustic monitoring has enormous potential in avian conservation, our results highlight the importance of understanding behaviour when using passive acoustic monitoring to estimate density and distribution.

Date
01 April 2020
RSPB Authors
Saskia Wischnewski
Authors
Arneill, Gavin E Critchley, Emma Jane Wischnewski, Saskia Jessopp, Mark J Quinn, John L
Published in
Ibis
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Variation in foraging strategies over a large spatial scale reduces parent–offspring conflict in Manx shearwaters

Parental care can lead to a conflict of interest between parents and offspring. For central place foragers, conflict is expected to be particularly intensive in species that feed on relatively inaccessible, distant food resources.

Date
01 April 2019
RSPB Authors
Saskia Wischnewski
Authors
Wischnewski, Saskia Arneill, Gavin E. Bennison, Ashley W. Dillane, Eileen Poupart, Timothée A. Hinde, Camilla A. Jessopp, Mark J. Quinn, John L.
Published in
Animal Behaviour 151: 165-176.
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