Table of Contents
Acknowledgements 6
Scope of the Book 7
How Birds Navigate 9
The four avian compasses 10
The avian clock - deciding when to stop migrating 16
The avian map sense and 'true' navigation 17
Vagrancy Through Compass Errors 21
Reverse migration as a cause of vagrancy 21
Reverse migration in spring 24
Mirror-image misorientation 26
Compass errors and the axis of migration 28
Magnetic anomalies 28
Limitations to the reverse migration and mirror-image hypotheses 30
Vagrancy in social migrants 33
Wind Drift and Vagrancy 36
The sky as a complex habitat 37
How do birds respond to wind drift? 40
Wind drift over water 41
Global transoceanic vagrancy patterns 42
Jet streams and vagrancy 45
Overshooting 46
Overshooting in spring and autumn 46
How overshooting works 47
Extreme Weather and Irruptions 49
Storms and seabirds 49
Irruptions and nomadism as a cause of vagrancy 51
Vagrancy and Natural Dispersal 53
Exploratory vagrancy in resident species 54
Exploratory vagrancy in migratory species 55
Human-Driven Vagrancy 57
Indirect human impacts affecting vagrancy 61
Consequences of Vagrancy for Species and Ecosystems 63
Establishing new breeding locations 63
Colonisation of new winter sites and migratory routes 66
Impacts on other species and ecosystems 68
Family Accounts 71
Avian Vagrancy in an Era of Global Change 330
The future of rare bird discovery and 'twitching' 331
Advances in the scientific understanding of vagrancy and future research directions 333
References 335
General Index 374
Species Index 375
