Reintroduction ecology of the Eurasian crane Grus grus

Successful conservation strategies to increase the survival prospects of a population must be accompanied by an accurate knowledge of the population dynamics. In this thesis, I examine the population dynamics of Eurasian cranes (Grus grus) in the UK and assess the impact of a reintroduction on the future population size and distribution. Additionally, I cover other aspects of crane conservation, such as public engagement in crane conservation and crane resilience to extreme weather events. To do so, I use a wide range of tools: Internet-based monitoring methods, stochastic matrix population models, point process models and GPS-accelerometer tracking devices. I show that there is a geographic gradient in interest in reintroduction projects; people living near the project area have a greater interest than people from areas further away. I also show that the UK crane population is acting as a pseudo-sink; current levels of survival and productivity allow the population’s persistence but immigration is driving population recovery. Nevertheless, the productivity of the UK population is low and measures to improve it should be implemented. The reintroduction of 90 birds in the Somerset Levels has decreased the relative importance of immigration and is likely to increase the projected population size by 50% over the next 50 years. However, the increase in population numbers will not be accompanied by a large expansion in the population range. Cranes will likely colonize large wetlands with low perimeter-to-area ratios near already occupied areas, but the reintroduction will increase the dispersal potential of the species. Finally, I find that during an extreme flooding event, crane foraging areas became limited to a small unflooded patch, but cranes coped with this event through behavioural flexibility, by increasing their foraging time. Together, these results highlight the importance of reaching a broad understanding of population dynamics in order to implement effective conservation strategies