Potential Effects of Climate Change on the Distribution and Migration of European Breeding Migratory Birds

Abstract

Aim: This thesis aims to investigate the potential impacts of climatic change on Afro-Palaearctic migratory birds by investigating simulated changes in breeding and non-breeding distribution.
Methods: Generalised Additive Models were used to determine those climatic variables that produced the most robust species distribution models. Tests on the performance of three regression-based techniques were undertaken and consensus modelling framework was subsequently chosen. This framework was used in conjunction with three general circulation models and two emission scenarios to model the future distributions of Afro-Palaearctic migratory birds. Changes in both breeding and non-breeding range and migratory distance were examined for groups of species. A vulnerability index was created to indicate those species that were most vulnerable to climate change. Finally, changes in recent population trends observed on the European breeding grounds were related to simulated climatic suitability to investigate the role of climate in recent population changes and determine the vulnerability of populations to climate change. This analysis also enabled a partial validation of species distribution models.
Results: The results indicate differential change on the breeding and non-breeding grounds for many species. For many migratory birds a progressive separation of the two ranges is projected, potentially increasing migratory distances in future. However, for some species newly suitable climatic areas may provide non-breeding areas closer to the breeding range, enabling species to adapt to climatic change. Trans-Saharan migrants, species residing in dry environments as well as montane and coastal species are projected to be most vulnerable to climatic change. Although a link between population trends and climatic suitability could be found, the results indicated, as might be expected, that climate is only one of a number of factors potentially contributing to population changes
Conclusion: This thesis gives the first broad analysis of the likely direction and magnitude of change of the distribution of migratory birds to climate change, when only climate is considered. The challenge ahead is to refine these coarse scale models to include habitat and demographic data so as to provide more realistic estimates of change and improve conservation strategies that aim to support species under climate change.