Publications for Dr Mark Bolton

Upwelling systems in the migration ecology of Roseate Terns (Sterna dougallii) breeding in northwest Europe

For migratory seabirds, staging and wintering areas may be important targets for conservation. Declines of Roseate Tern Sterna dougallii populations have led to conservation initiatives at breeding sites on both sides of the North Atlantic. However, these could be compromised by environmental conditions in non-breeding areas. The migratory ecology of Roseate Terns is poorly known and we used light-level biologgers (geolocators) to identify the migratory routes, staging and wintering areas of Roseate Terns from two European colonies. Most birds wintered off the Ghanaian coast in the Gulf of Guinea, but some wintered further west off Sierra Leone and Liberia, or changed locations during the winter. In these areas, cold-water upwellings of the Guinea Current Large Marine Ecosystem (GCLME) may provide vital foraging resources. Geolocations in combination with temperature measurements and satellite sea-surface temperature data show that cold-water upwellings of the Canary Current Large Marine Ecosystem (CCLME) were important areas for migratory staging, particularly on the return migration which was slower than the outward journey. These results emphasize the importance of productive cold-water upwellings in the migratory ecology of Roseate Terns. The GCLME and CCLME are under threat from over-exploitation, pollution and climate change; effective conservation of these environments will be important to secure the long-term future of these and other seabirds.

Date
01 April 2021
RSPB Authors
Dr Mark Bolton
Authors
Redfern, Chris PF Kinchin‐Smith, David Newton, Stephen Morrison, Paul Bolton, Mark Piec, Daniel
Published in
Ibis 163 (2): 549-565
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Effect of GPS tagging on behaviour and marine distribution of breeding Arctic Terns Sterna paradisaea

Tracking tags have been used to map the distributions of a wide variety of avian species, but few studies have examined whether the use of these devices has impacts on the study animals that may bias the spatial data obtained. As Global Positioning System (GPS) tags small enough for deployment on terns (family: Laridae) have only recently become available, until now tracking of this group has been conducted by following unmanipulated individuals by boat, which offers a means of comparing distributions obtained from GPS-tracking. We compared the utilization distributions (UDs) of breeding Arctic Terns Sterna paradisaea obtained by GPS-tracking 10 individuals over 2 weeks, with UDs derived from contemporaneous visual boat tracks from 81 individuals. The 50% and 95% UDs of both methods had high similarity scores, indicating good agreement in the density distributions derived from the two methods. The footprints of the UDs of tagged birds were ~ 75–80% larger, which may reflect an effect of tagging on foraging range or the occasional inability to follow by boat individuals which roamed further from the colony. We also compared the nest attendance and chick provisioning rates of adults that were (1) fitted with a GPS tag and leg-flag, (2) handled and marked with a leg-flag but not tagged and (3) fitted with a leg-flag in a previous year but unhandled in the year of the study. There was some evidence that birds fitted with both a GPS tag and leg-flag spent slightly less time at the nest compared with unhandled birds and those fitted with a leg-flag only. Both treatments where birds were fitted with a leg-flag in the year of the study had similarly lower provisioning rates to those of unhandled control birds > 48 h after handling, suggesting that negative effects on provisioning are due to capture and handling or leg-flag attachment rather than to GPS tag attachment/loading per se. Overall brood-provisioning rate was compensated for by the increased effort by the unhandled partner. Our study suggests that despite slight effects of GPS-tagging on behaviour, the estimates of marine density distribution obtained were very similar to those of unmanipulated birds.

Date
01 January 2021
RSPB Authors
Stephen Dodd, Dr Ian Johnstone, Dr Mark Bolton
Authors
Seward, Adam Taylor, Rachel C Perrow, Martin R Berridge, Richard J Bowgen, Katharine M
Published in
Ibis 163 (1): 197-212
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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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GPS tracking reveals highly consistent use of restricted foraging areas by European Storm-petrels Hydrobates pelagicus breeding at the largest UK colony: implications for conservation management

Seabirds face a diverse array of threats and are considered to comprise one of the most threatened avian groups globally. Development of appropriate conservation action requires a knowledge of the marine distribution of seabirds, furnished either by tracking the movements of individuals, or from at-sea surveys. Obtaining information on the distribution of the smallest seabird species, the storm-petrels Hydrobatidae, is challenging, but the recent development of <1 g GPS tracking tags now enables high-precision tracking and this study reports the first multi-year high-precision tracking of European Storm-petrels Hydrobates pelagicus from their largest UK breeding colony. A total of 42 successful tag deployments were made over four breeding seasons during incubation, brooding and post-brood phases, and there was no evidence of adverse impacts on adult body mass or nest survival rates. Foraging trips lasted between one and three days and ranged up to 397 km from the colony (median = 159 km). Foraging range and total distance covered were positively correlated with trip duration but did not differ across breeding stages. Storm-petrels did not feed to the west of the colony at the edge of the continental shelf where high concentrations have been reported in previous decades from boat surveys, but rather, foraging was restricted to shallow waters south of the colony, consistent across individuals, breeding stages and years. Two areas were identified that exceed the threshold criteria for marine Important Bird Area status and should be considered for statutory protection. The home range estimated across all three breeding stages overlapped with 206 active hydrocarbon wells and 14 operating platforms which represent potential threats as sources of surface pollution or through attraction of birds to gas flares. Improved understanding of the foraging distribution of storm-petrels from this protected colony greatly assists the identification of potential threats and informs appropriate marine spatial planning.

Date
02 September 2020
RSPB Authors
Dr Mark Bolton
Published in
Bird Conservation International 31 (1) : 35-52
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What can seabirds tell us about the tide?

Small global positioning system (GPS) trackers are now routinely used to study the movement and behaviour of birds at sea. If the birds rest on the water they become "drifters of opportunity" and can be used to give information about surface currents. In this paper, we use a small data set from satellite-tracked razorbills...

Date
01 November 2019
RSPB Authors
Dr Mark Bolton, Dr Ellie Owen, Stephen Dodd
Authors
Cooper, M., Bishop, C., Lewis, M., Bowers, D., Bolton, M., Owen, E. & Dodd, S.
Published in
Ocean Science 14 (6): 1483-1490
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Environmental heterogeneity decreases reproductive success via effects on foraging behaviour

Environmental heterogeneity shapes the uneven distribution of resources available to foragers, and is ubiquitous in nature. Optimal foraging theory predicts that an animal's ability to exploit resource patches is key to foraging success

Date
03 June 2019
RSPB Authors
Dr Ellie Owen, Dr Mark Bolton, Dr Kendrew Colhoun
Authors
Alice M. Trevail Jonathan A. Green Jonathan Sharples Jeff A. Polton Peter I. Miller Francis Daunt Ellie Owen Mark Bolton Kendrew Colhoun Stephen Newton Gail Robertson Samantha C. Patrick
Published in
Proceedings of the Royal Society B: Biological Sciences 286(1904): 20190795.
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A Migratory Divide Among Red-Necked Phalaropes in the Western Palearctic Reveals Contrasting Migration and Wintering Movement Strategies

Non-breeding movement strategies of migratory birds may be expected to be flexibly adjusted to the distribution and quality of habitat, but few studies compare movement strategies among populations using distinct migration routes and wintering areas

Date
01 April 2019
RSPB Authors
Dr Mark Bolton
Authors
van Bemmelen, R. S. A. Kolbeinsson, Y. Ramos, R. Gilg, O. Alves, J. A. Smith, M. Schekkerman, H. Lehikoinen, A. Petersen, I. K. Porisson, B. Sokolov, A. A. Valimaki, K. van der Meer, T. Okill, J. D. Bolton, M. Moe, B. Hanssen, S. A. Bollache, L. Petersen, A. Thorstensen, S. Gonzalez-Solis, J. Klaassen, R. H. G. Tulp, I.
Published in
Frontiers in Ecology and Evolution 7: 86.
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A review of the occurrence of inter-colony segregation of seabird foraging areas and the implications for marine environmental impact assessment

Understanding the determinants of species' distributions is a fundamental aim in ecology and a prerequisite for conservation but is particularly challenging in the marine environment. Advances in bio-logging technology have resulted in a rapid increase in studies of seabird movement and distribution in recent years. Multi-colony studies examining the effects of intra- and inter-colony competition on distribution have found that several species exhibit inter-colony segregation of foraging areas, rather than overlapping distributions. These findings are timely given the increasing rate of human exploitation of marine resources and the need to make robust assessments of likely impacts of proposed marine developments on biodiversity. Here we review the occurrence of foraging area segregation reported by published tracking studies in relation to the density-dependent hinterland (DDH) model, which predicts that segregation occurs in response to inter-colony competition, itself a function of colony size, distance from the colony and prey distribution. We found that inter-colony foraging area segregation occurred in 79% of 39 studies. The frequency of occurrence was similar across the four seabird orders for which data were available, and included species with both smaller (10-100 km) and larger (100-1000 km) foraging ranges. Many predictions of the DDH model were confirmed, with examples of segregation in response to high levels of inter-colony competition related to colony size and proximity, and enclosed landform restricting the extent of available habitat. Moreover, as predicted by the DDH model, inter-colony overlap tended to occur where birds aggregated in highly productive areas, often remote from all colonies. The apparent prevalence of inter-colony foraging segregation has important implications for assessment of impacts of marine development on protected seabird colonies. If a development area is accessible from multiple colonies, it may impact those colonies much more asymmetrically than previously supposed. Current impact assessment approaches that do not consider spatial inter-colony segregation will therefore be subject to error. We recommend the collection of tracking data from multiple colonies and modelling of inter-colony interactions to predict colony-specific distributions.

Date
01 April 2019
RSPB Authors
Dr Mark Bolton
Authors
Bolton, M. Conolly, G. Carroll, M. Wakefield, E. D. Caldow, R.
Published in
Ibis
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Spatial scales of marine conservation management for breeding seabirds

Knowing the spatial scales at which effective management can be implemented is fundamental for conservation planning. This is especially important for mobile species, which can be exposed to threats across large areas, but the space use requirements of different species can vary to an extent that might render some management approaches inefficient.

Here the space use patterns of seabirds were examined to provide guidance on whether conservation management approaches should be tailored for taxonomic groups with different movement characteristics.

Seabird tracking data were synthesised from 5419 adult breeding individuals of 52 species in ten families that were collected in the Atlantic Ocean basin between 1998 and 2017. Two key aspects of spatial distribution were quantified, namely how far seabirds ranged from their colony, and to what extent individuals from the same colony used the same areas at sea.

There was evidence for substantial differences in patterns of space-use among the ten studied seabird families, indicating that several alternative conservation management approaches are needed. Several species exhibited large foraging ranges and little aggregation at sea, indicating that area-based conservation solutions would have to be extremely large to adequately protect such species.

The results highlight that short-ranging and aggregating species such as cormorants, auks, some penguins, and gulls would benefit from conservation approaches at relatively small spatial scales during their breeding season. However, improved regulation of fisheries, bycatch, pollution and other threats over large spatial scales will be needed for wide-ranging and dispersed species such as albatrosses, petrels, storm petrels and frigatebirds.

Date
03 December 2018
RSPB Authors
Dr Steffen Oppel, Dr Mark Bolton, Dr Ellie Owen
Authors
Oppel, S., Bolton, M., Carneiro, A.P.B., Dias, M.P., Green, J.A., Masello, J.F., Phillips, R.A., Owen, E., Quillfeldt, P., Beard, A., Bertrand, S., Blackburn, J., Boersma, P.D., Borges, A., Broderick, A.C., Catry, P., Cleasby, I., Clingham, E., Creuwels, J., Crofts, S., Cuthbert, R.J., Dallmeijer, H., Davies, D., Davies, R., Dilley, B.J., Dinis, H.A., Dossa, J., Dunn, M.J., Efe, M.A., Fayet, A.L., Figueiredo, L., Frederico, A.P., Gjerdrum, C., Godley, B.J., Granadeiro, J.P., Guilford, T., Hamer, K.C., Hazin, C., Hedd, A., Henry, L., Hernandez-Montero, M., Hinke, J., Kokubun, N., Leat, E., Tranquilla, L.M., Metzger, B., Militao, T., Montrond, G., Mullie, W., Padget, O., Pearmain, E.J., Pollet, I.L., Putz, K., Quintana, F., Ratcliffe, N., Ronconi, R.A., Ryan, P.G., Saldanha, S., Shoji, A., Sim, J., Small, C., Soanes, L., Takahashi, A., Trathan, P., Trivelpiece, W., Veen, J., Wakefield, E., Weber, N., Weber, S., Zango, L., Daunt, F., Ito, M., Harris, M.P., Newell, M.A., Wanless, S., Gonzalez-Solis, J. & Croxall, J.
Published in
Marine Policy 98: 37-46
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Combined bottom-up and top-down pressures drive catastrophic population declines of Arctic skuas in Scotland

Understanding drivers of population change is critical for effective species conservation. In the northeast Atlantic Ocean, recent changes amongst seabird communities are linked to human and climate change impacts on food webs. Many species have declined severely, with food shortages, and...

Date
01 November 2018
RSPB Authors
Dr Allan Perkins, Dr Mark Bolton
Authors
Perkins, A., Ratcliffe, N., Suddaby, D., Ribbands, B., Smith, C., Ellis, P., Meek, E. & Bolton, M.
Published in
Journal of Animal Ecology 87 (6): 1573-1586
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