Vagrancy theories: Are autumn vagrants really reverse migrants?

James J. Gilroy, Alexander C. Lees

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69 Citations (Scopus)


Reverse migration is a popular concept, often used to explain the occurrence of autumn vagrants. The term 'reverse migration shadow' has been used to identify regions in which autumn vagrancy of a given species may occur, and to predict potential future vagrants to Britain. In this paper, we evaluate this theory and, by analysing vagrancy patterns, demonstrate that autumn vagrancy is not limited to the 'shadow' of a 180° route-reversal. Although the vast majority of individuals follow a traditional route to winter quarters, vagrancy during autumn migration occurs in all directions, and we contend that it is the pattern of observer coverage which determines the number of vagrants discovered. The occurrence patterns of some vagrants reaching Britain can be explained using the idea of long-range dispersal. We suggest that some comparatively regular vagrants reaching Britain are, in fact, performing annual migrations to presently undiscovered wintering grounds in western Europe or West Africa.

Original languageEnglish
Pages (from-to)427-438
Number of pages12
JournalBritish Birds
Issue number9
Publication statusPublished - Sep 2003

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