Human-driven habitat change: impacts on Herring Gull populations and shifting conservation conflicts.

Environmental change is altering natural resource availability across marine and terrestrial habitats. These changes at a regional scale may reduce opportunities in one habitat but can create new opportunities in others for mobile species that can travel across several habitats. While food in natural habitats can be reduced, human activity can offer new and more predictable food resources (Fehlmann et al. 2021). Altered availability of different environments within an individual’s home range may have consequences for its survival and reproduction. It is, however, difficult to predict what will be the consequences of these changes for entire populations. Altered relative use of resources in different habitats can also lead to changes in interactions between wildlife and humans that can have both positive and negative effects on humans and wildlife populations. It is therefore important to understand, and predict, the impact of changes in the availability of different environments on (1) changes in population abundance and (2) on shifting conservation conflicts.

To understand (1) how populations respond to changes in the availability of different environments we can use a framework of Matthiopoulos (2022) and Matthiopoulos et al. (2011, 2015), which accounts for individuals responding to the habitat characteristics of their immediate location as well as to the overall habitat composition in their home range (e.g., the availability of all habitats within their entire home range). If the species is examined across a range of environmental scenarios, it is possible to evaluate how changes in the availability of different environments affects the population and predict how species will respond to environmental changes (Matthiopoulos et al. 2015, 2019). To understand (2) how changes in habitat use by one species impacts on the use of that environment by human stakeholders we can explore association between that environment and local stakeholder communities using participatory mapping to identify potential trade-offs between stakeholders that promote wildlife conservation and those that are negatively affected and impacted by wildlife (Stosch et al. 2019, 2022). Based on a curve of conflict model we can model the dynamics of conservation conflicts under different environmental change scenarios (Cusack et al. 2020). These insights into hotspots of conflict under what circumstances conflicts are likely to intensify can be used to work towards shared solutions that all stakeholders can accept and that will ultimately benefit wildlife conservation and the socioeconomic interests of local community stakeholders.

Large gulls are opportunistic generalists that use both marine and terrestrial environments to different extents. Herring Gulls (Larus argentatus) have undergone large scale declines over the last four decades in the UK and are currently on the red list of the Birds of Conservation Concern. Gulls are also protected features in several Special protection Areas (SPAs) around the UK. However, the drivers of declines are not well understood. Furthermore, despite the decline in absolute numbers, Herring Gulls have expanded the habitats they use including those where they can come into conflict with human activities and interests, especially in more built-up areas. A recent study on Herring Gull populations in the Netherlands, found spatial variation in survival rates but no link between colony trajectories and age- and colony-specific survival (Kentie et al. 2022). In the UK, Herring Gulls also show spatial variation in population trajectories among colonies and regions (Nager & O’Hanlon 2016, O’Hanlon & Nager 2018). It is likely that there is no universal cause of changes in numbers and distribution, but rather, factors that act at a local and regional scale are driving change. For conservation and policy managers, a better understanding of how impacts at the local scale may drive changes in gull numbers has been identified as a key knowledge gap. This project aims to quantify the impact of altered terrestrial and marine environments on Herring Gull population abundance, changes in use of habitats and conflicts arising with other users of the same environments.

Given that the habitats and resources Herring Gulls use within the home range of the breeding colony likely influence its demography, we plan to implement recent developments in quantifying species-habitat associations (Matthiopoulos et al. 2020) to evaluate the impact of landscape changes on population trajectories. A better understanding of how habitat use links to population growth could lead to informing management plans that regain favourable population trajectories of Herring Gulls. Increasing gull populations in built-up areas also mean increasing impacts on people (harassment, fouling, noise) which are identified by mapping potential trade-offs between stakeholders that promote the conservation of gulls and those that are negatively affected and impacted by them (e.g., tourism, shops, recreation). This will allow the identification of conflict hotspots as well as developing coexistence scenarios. This will not only contribute to a better understanding between different stakeholder groups but work towards shared solutions that all stakeholders can accept and that will ultimately benefit conservation of gulls and socioeconomic interests of stakeholders (e.g., eco-tourism, zoning).

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Image Captions

Herring Gulls (photo: Ruedi Nager)


The first step of this PhD will involve working with existing tracking datasets to provide a better understanding of habitat use of Herring Gulls across areas that vary in the availability of different environments. Tracking data from breeding Herring Gulls are available for up to seven different areas across Scotland, Northern Ireland and England from the University of Glasgow and the BTO. Additional field surveys will be carried out to sample gull area/habitat use within the gulls’ home range (Woodward et al. 2019). The tracking and survey data will be used to identify key habitats used by gulls. Additional observations at these key habitats will record what the gulls are actually eating there. While the project will initially focus on the breeding season, for some sites we also have data from the full annual cycle (O’Hanlon et al. 2022) and the project can be expanded to also include the non-breeding season. Environmental data on habitat availability will be extracted from the national Landcover dataset, as well as from additional sources for fisheries and landfill sites. Data on potential drivers of decline not related to habitat use (i.e. culling/legal lethal control/predation/disease) will also be located for the specific study sites.

To test the hypothesis that the availability of habitats and resources Herring Gulls use within their foraging range influence its demography, the student will implement generalised functional responses and habitats-to-population framework (Matthiopoulos et al. 2011, 2019) that incorporates interactions between different environments. This would be followed by linking habitat use to population performance via the habitat-to-population model, which will require colony counts obtained from the publicly accessible Seabird Monitoring Programme (SMP). In this database there are currently at least 50 colonies with sufficient numbers of counts that can be used for this analysis. This will allow the student to evaluate whether habitat composition explains population performance better than other potential drivers of population change.

The student will use stakeholder consultation and focus group discussions to map areas of perceived trade-offs and conflicts between gull conservation and human activities and interests. Data on stakeholder perceptions of conflicts will be collected using participatory mapping approaches using maps of current and predicted gull habitat use gained from this study. This information will then also be used to predict changes in human-gull conflicts under different environmental change scenarios to identify environments where these conflicts will intensify and where they may diminish. The results of this project will be used to provide information to relevant stakeholders to inform management plans for Special Protection Areas (SPAs) with gulls as qualifying features, as well as in helping understand mitigation strategies of stakeholder conflicts and identifying areas of emerging conflict.

Project Timeline

Year 1

Literature review

Getting familiar with the available data

Identifying environmental dataset relevant for the habitat use modelling

Organising and carrying out observational fieldwork

Preliminary analysis of data collected during first field season

Training in spatial ecology and generalised functional response framework

Year 2

Additional observational fieldwork to build on that carried out in Year 1

Implement generalised functional responses and habitats-to-population framework for the selected sites

Write-up of the outcomes of generalised functional responses and habitats-to-population analyses for individual publications

Attendance of appropriate ecological and ornithological conferences to report on the outcomes of the project

Year 3

Carry out stakeholder consultations and focus group discussions in combination with participatory mapping and curve of conflict models predicting dynamics of conservation conflicts under different environmental change scenarios.

Attendance of appropriate ecological and ornithological conferences to report on the outcomes of the project

Write up of thesis and papers for peer-review publication

Year 3.5

Finalising thesis write up

& Skills

In this project the student will have an opportunity to explore holistically a conservation conflict using both state of the art species-habitat association methods and participatory approaches to consider interests of shared stakeholders. This will be achieved by working with a team that brings together field work expertise, spatial modelling and work at the interface between biodiversity and society combining natural and social sciences to improve our understanding of decision making in conservation. This will provide a range of training opportunities including: (i) fieldwork skills in surveying for habitat use and resource use; (ii) access to and use of GPS tracking datasets of Herring Gulls from multiple colonies; (iii) quantitative skills in analysing spatially explicit data and population modelling; and (iv) tools in quantifying intensity and dynamics of conservation conflicts.

The student will also have opportunities for working with the BTO and NatureScot to gain experience and insight in conservation management and policy making.

References & further reading

Cusack, J.J, Bradfer-Lawrence, T., Zachary Baynham-Herd, Z., Castelló y Tickell, S., Duporge, I., Hegre, H., Moreno Zárate, L., Naude, V., Nijhawan, S., Wilson, J., ZambranoCortes, D.G. & Bunnefeld, N. 2020. Measuring the intensity of conflicts in conservation Conservation Letters 14: e12783.
Fehlmann, G., O’Riain, M. J., Fürtbauer, I. & King, A. J. 2021. Behavioral causes, ecological consequences, and management challenges associated with wildlife foraging in human-modified landscapes. BioScience 71: 40–54.
Kentie, R., Shamoun-Baranes, J., Spaans, A.L. & Camphuysen, K.C.J. 2022. Spatial patterns in age- and colony-specific survival in a long-lived seabird across 14 contrasting colonies. Ibis (Lond. 1859). 0–1.
Langley, L.P., Bearhop, S., Burton, N.H.K., Banks, A.N., Frayling, T., Thaxter, C.B., Clewley, G.D., Scragg, E. & Votier, S.C. 2021. GPS tracking reveals landfill closures induce higher foraging effort and habitat switching in gulls. Mov. Ecol. 9: 1–13.
Matthiopoulos, J. 2022 Defining, estimating, and understanding the fundamental niches of complex animals in heterogeneous environments. Ecological Monographs https://doi.org/10.1002/ecm.1545
Matthiopoulos, J., Hebblewhite, M. & Aarts, G. 2011. Generalized functional responses for species distributions. Ecol. Evol. 92: 583–589.
Matthiopoulos, J. , Fieberg, J., Aarts, G., Beyer, H.L., Morales, J.M. & Haydon, D.T. 2015. Establishing the link between habitat selection and animal population dynamics. Ecological Monographs, 85: 413-436.
Matthiopoulos, J., Field, C. & MacLeod, R. 2019. Predicting population change in nature from models based on habitat availability and utilisation. Proc. R. Soc. B 286: 20182911.
Matthiopoulos, J., Fieberg, J.R & Aarts, G. 2020. Species-Habitat Associations: Spatial data, predictive models, and ecological insights. University of Minnesota Libraries Publishing.
Nager, R.G. & O’Hanlon, N.J. 2016. Changing numbers of three gull species in the British Isles. Waterbirds 39: 15–28.
O’Hanlon, N.J. & Nager, R.G. 2018. Identifying habitat-driven spatial variation in colony size of Herring Gulls Larus argentatus. Brit. Birds 65: 306-316.
O’Hanlon, N.J., Thaxter, C.B., Burton, N.H.K., Grant, D., Clark, N.A., Clewley, G.D., Conway, G.J., Barber, L.J., McGill, R.A.R. & Nager, R.G. 2022. Habitat Selection and Specialisation of Herring Gulls During the Non-breeding Season. Front. Mar. Sci. 9: 816881.
Stosch, K.C., Quilliam, R.S., Bunnefeld, N. & Oliver, D.M. 2019. Quantifying stakeholder understanding of an ecosystem service trade-off. Science of The Total Environment 651: 2524-2534.
Stosch, K.C., Quilliam, R.S., Bunnefeld, N. & Oliver, D.M. 2022 Catchment-Scale Participatory Mapping Identifies Stakeholder Perceptions of Land and Water Management Conflicts Land 11: 300.
Woodward, I., Thaxter, C.B., Owen, E., Cook, A.S.C.P. 2019. Desk- based revision of seabird foraging ranges used for HRA screening. BTO Research Report No. 724. British Trust for Ornithology, Thetford

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