Dr Mark Bolton

Principal Conservation Scientist, Conservation Science

Background

Since 2008 I have overseen the RSPB's UK marine research programme and work with a fantastic team of scientists, policy colleagues and regional staff to provide the scientific evidence to address seabird conservation problems, identifying causes of population decline, and their potential solutions.

Our work enables our policy and regional colleagues to advocate for, and implement, action to address seabird conservation concerns. We manage a large programme of seabird tracking to identify marine areas that are important for seabirds and assess potential marine threats.

We also work closely with the Seabird Island Restoration team to identify locations and management actions that will improve conditions for nesting seabirds. We make full use of the latest gadgets, such as miniature tracking tags and thermal cameras.

External Activities

  • 2010 to present: Director, Fair Isle Bird Observatory, and Chair of the Science Committee
  • 2020 to present: Advisory Panel of "Birds on the Brink" conservation charity (https://www.birdsonthebrink.co.uk/)
  • Peer reviewer for a large number of international scientific journals

Partners and Collaboration

  • Professor Pat Monaghan, Glasgow University
  • Dr Jonathan Green, Liverpool University
  • Dr Francis Daunt, CEH UK
  • Dr Rob Thomas, Cardiff University
  • Professor Vicki Friesen, Queens University, Canada
  • Dr Norman Ratcliffe, British Antarctic Survey
  • Dr Ollie Paget, Oxford University
  • Dr Matt Wood, Gloucestershire University
  • Dr Ewan Wakefield, Glasgow University
  • Dr Veronica Neves, University of Azores
  • Dr Chris Redfern, Newcastle University

Contact

Mark Bolton

Dr Mark Bolton

Principal Conservation Scientist, Conservation Science

RSPB UK Headquarters, The Lodge, Sandy, Bedfordshire, SG19 2DL

mark.bolton@rspb.org.uk

Google Scholar

Specialisms

Identifying problems Marine New methods and technologies Protected areas UK species

Selected Publications

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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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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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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Metapopulation dynamics of roseate terns: Sources, sinks and implications for conservation management decisions

Habitat management to restore or create breeding sites may allow metapopulations to increase in size and reduce the risk of demographic stochasticity or disasters causing metapopulation extinction. However, if newly restored or created sites are of low quality, they may act as sinks that draw individuals away from better quality sites to the detriment of metapopulation size. Following intensive conservation effort, the metapopulation of roseate tern (Sterna dougallii) in NW Europe is recovering from a large crash in numbers, but most former colonies remain unoccupied and hence are potential targets for restoration. To inform conservation efforts, we studied the dynamics of this metapopulation with a multistate integrated population model to assess each of the three main colonies for important demographic contributors to population growth rate, source/sink status and possible density dependence. All three study colonies are managed for roseate terns (and other tern species) in similar ways, but the demographic processes vary considerably between colonies. The largest colony is a source involved in almost all dispersal, and its growth is determined by survival rates and productivity. Productivity and juvenile apparent survival at the largest colony appear to be density-dependent. Although the mechanisms are unclear, this may provide an increasing impetus for emigration of recruits to other colonies in future. The smallest of the three colonies is a sink, relying on immigration for its growth. Simulation models suggest the metapopulation would be c. 10% larger in the absence of dispersal to the sink colony. This work indicates that, due to variable site quality, aims to enhance both distribution and size of metapopulations may be mutually exclusive. In this case, before future attempts to encourage recolonisation of former sites, assessments of site suitability should be undertaken, focusing on food availability and isolation from predators to maximise the likelihood of attaining levels of productivity and survival that avoid creation of a sink population to the detriment of the overall metapopulation size.

Date
23 October 2018
RSPB Authors
Dr Mark Bolton
Authors
Seward, A. Ratcliffe, N. Newton, S. Caldow, R. Piec, D. Morrison, P. Cadwallender, T. Davies, W. Bolton, M.
Published in
Journal of Animal Ecology
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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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