Linda Wilson

Insights from colour-ringing little terns Sternula albifrons across Britain, Ireland and the Isle of Man

Little terns are one of our rarest seabirds and understanding what drives their population dynamics is key to informing how we prioritise and direct conservation efforts. However, our knowledge of key aspects of little tern demography such as survival rate, recruitment and dispersal, is poor due to low recovery rates of metal-ringed birds and challenges associated with mark-recapture studies for this species. In 2014, a five-year EU LIFE+ Little Tern Recovery Project initiated the first multi-colony little tern colour-ringing scheme in Britain and was complemented by initiatives in Ireland, the Isle of Man and Teesside. Here we summarise the insights gained from these projects so far, including revealing the extensive movements and exchanges between colonies, records of birds returning to their breeding quarters in their first-summer, confirmed breeding by two-year-old birds, along with reports of birds at their wintering grounds in West Africa and on their migration routes

Date

01 February 2021

RSPB Authors

Linda Wilson, Dr Mark Bolton

Authors

Rendell-Read, S. Brown, C. Candelin, G. Cook, H. Hales, S. Lock, L. Newton, S. Norman, D. Samson, L. Slattery, J. Williams, L.J.

Published in

British Birds

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Effectiveness of a five-year project of intensive, regional-scale, coordinated management for little terns Sternula albifrons across the major UK colonies

Little terns in the UK have undergone a population decline of 37 % over the last three decades despite protection efforts at their breeding sites during this time. In 2014, a five-year Little Tern Recovery Project was launched in the UK through the European Union LIFE + funding stream, deploying a more coordinated, comprehensive and strategic programme of conservation measures at 29 breeding sites across England and Wales. We compared little tern productivity (fledging probability per egg) during the project with that experienced in the five years prior to the project and included data from both project sites and reference sites. We found a positive relationship between productivity and colony size as well as differences in productivity between ‘northern’ and ‘southern’ regions of the UK, with colonies in the northern region doing better. There was a positive effect on productivity associated with the project’s enhanced measures, but this interacted negatively with colony size, such that increased productivity was only seen for colonies with ≤91 pairs (which comprised 90 % of our dataset). Although average modelled breeding success across all project sites during the project was low (0.37 chicks/pair), we found it was on average more than double (164 % increase) than it would have otherwise been in the absence of the enhanced management measures. For colonies with ≤91 pairs, the predicted increase was 208 %. However, for colonies >91 pairs, there was a predicted 20 % reduction in breeding success in the presence of enhanced management. This counter-intuitive result may be due to threats at larger sites already being managed as far as practicable prior to the project, and poor breeding success during the project being mainly due to stochastic, less manageable threats such as severe weather. In addition, fewer data were available to inform the model for larger colonies. Overall, we estimate that an additional 1,785 chicks fledged as a result of the project. Those that survive their first few years are expected to recruit back into the UK and Irish population, benefitting from the legacy of protection, habitat restoration and creation measures established as part of the project. However, a simple population model indicates that even if the elevated breeding success levels achieved by the project were maintained, the projected population decline between 2020–2050 would only be slowed by 30 %, so more needs to be done to achieve population stabilisation. However, the project’s beneficial impact has bought valuable time that can be used to further develop and deploy innovative solutions.

Date

01 February 2020

RSPB Authors

Linda Wilson, Dr Mark Bolton

Authors

Rendell-Read, S Lock, L Drewitt, AL

Published in

Journal for Nature Conservation

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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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Assessing bycatch risk from gillnet fisheries for three species of diving seabird in the UK

Incidental mortality (bycatch) in fisheries represents a threat to marine vertebrates. Research has predominantly focussed on bycatch in longline fisheries, but bycatch from gillnet fisheries is of increasing concern. To address this concern, we combined comprehensive biologging data sets and multiple sources of fishing effort data to assess the spatial overlap of 3 diving seabird species during the breeding season (common guillemot Uria aalge, razorbill Alca torda and European shag Phalacrocorax aristotelis) with UK gillnet fisheries. Species distribution models based on birds’ diving behaviour identified areas of elevated bycatch risk where high levels of diving activity and fishing effort coincided. In addition, we identified times of day and water depths where diving activity, and hence bycatch risk, may be concentrated. Bycatch risk hotspots for all 3 species were identified along the north-east coast of England. Risk hotspots were also identified along the Pembrokeshire coast for both auk species and along the Cornish coast for shag. Lack of fishing effort data for smaller vessels made it difficult to assess seabird-fishery overlap in Scottish waters. Across species, diving activity was lower at night. For razorbill and guillemot, dive depth tended to increase at sunrise and decrease after sunset. For shag, dive depth showed no diel pattern but was associated with water depth. Our findings should assist in targeting spatio-temporal measures and designing deterrent devices to reduce bycatch. However, scarcity of data on the behaviour of gillnet fishers at comparable spatio-temporal resolution as seabird movement data remains a constraint to fully understanding seabird-fisheries interactions.

Date

17 February 2022

RSPB Authors

Ian Cleasby, Linda Wilson, Dr Ellie Owen, Dr Mark Bolton

Authors

Cleasby, Ian R Wilson, Linda J Crawford, Rory Owen, Ellie Rouxel, Yann Bolton, Mark

Published in

Marine Ecology Progress Series

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Identifying important at-sea areas for seabirds using species distribution models and hotspot mapping

Marine protected areas (MPAs) underpin the sustainable management of marine ecosystems but require accurate knowledge of species distributions. Recently, advances in tracking technology and habitat modelling have enabled the production of large-scale species distribution models (SDM), which provide the basis for hotspot mapping. In the UK, hotspot mapping to inform seabird MPA identification has involved converting observed or predicted distributions to polygons using either Maximum Curvature or Getis-Ord (Gi*) analysis. Here, we apply both mapping techniques to UK-wide, breeding season SDM predictions for four seabird species (Black-legged Kittiwakes Rissa tridactyla, Common Guillemots Uria aalge, Razorbills Alca torda and European Shags Phalacrocorax aristotelis) in order to compare their performance and inform seabird MPA. When using Maximum Curvature, grid cells within the identified maximum curvature boundaries were defined as hotspots. For Getis-Ord analysis, we defined hotspots as either (1) grid cells containing the top 1% or (2) the top 5% Gi* scores or (3) cells in which Gi* scores were statistically significant. Hotspots based upon Maximum Curvature or statistically significant Gi* scores covered the greatest area and were generally larger than current marine Special Protection Areas. Hotspots based on the top 1% or top 5% of Gi* scores were smaller and were concentrated around the largest breeding colonies. All hotspot methods consistently identified several high-density areas that should be prioritised for seabird conservation. Ultimately, the choice of hotspot identification method should be informed by considering species ecology alongside conservation goals to ensure hotspots are of sufficient size to protect target populations.

Date

01 January 2020

RSPB Authors

Ian Cleasby, Dr Ellie Owen, Linda Wilson, Dr Mark Bolton

Authors

Cleasby, Ian R Owen, Ellie Wilson, Linda Wakefield, Ewan D O'Connell, Peadar Bolton, Mark

Published in

Biological Conservation

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