The influence of environmental conditions on individual behaviour and population trends of European birds

Zalewska, Karolina (2026) The influence of environmental conditions on individual behaviour and population trends of European birds. Doctoral thesis, University of East Anglia.

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Abstract

Global biodiversity is facing multiple interconnected threats due to anthropogenic activity. Changes in land use can cause habitat loss and significant disturbance, which may lead to population declines. Climate change may bring about warming temperatures, as well as an increase in the frequency of extreme weather events. The extent to which different taxa may be affected by these changes will vary, and therefore, successful implementation of conservation action requires an understanding of the factors determining species vulnerability. Individual behavioural responses to current environmental conditions, such as spatiotemporal changes in activity and use of micro-refugia, may provide insights into strategies of coping with extreme weather. In this thesis, I assess the range of climatic conditions species experience within their breeding distributions as well as individual-level behaviour across the temperature gradient, to explore the effects of environmental change on species and individuals, using the little bustard (Tetrax tetrax) and the Eurasian kestrel (Falco tinnunculus) as model species representing the grassland bird community of Southern Europe, an area already experiencing severe climatic changes. I produce a metric of the climatic niche breadth of 159 European breeding bird species, accounting for range size, and relate this to the species’ population trends, to show that for species with similar range sizes, those experiencing a broader range of climatic conditions were less likely to be declining. I provide further evidence of a nuanced relationship between climatic niche breadth and range size and produce a metric that allows for the incorporation of this relationship into species vulnerability assessments. I then compare site usage by little bustards during the warmest part of the year and find that sites were more likely to be used if they were characterised by lower temperatures and greater microclimate refugia availability, but low shrubby cover. This suggests that while shrubs may provide microclimate refugia, too high shrub density may reduce site suitability. Finally, I investigate activity levels and micro-habitat use of Eurasian kestrels, and show that individuals were less active at higher temperatures and used trees as potential micro-refugia. The findings of this thesis highlight the crucial role of understanding individual behavioural responses in the face of extreme weather conditions, as well as the importance of micro-refugia availability for individual persistence under global warming.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Environmental Sciences
Depositing User:	Chris White
Date Deposited:	18 May 2026 10:48
Last Modified:	18 May 2026 10:48
URI:	https://ueaeprints.uea.ac.uk/id/eprint/103066
DOI:

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