Abstract
The Water Rail Rallus aquaticus is generally regarded as a facultative migrant in which migration patterns vary geographically. However, quantitative analyses of migration directions and how migration distances vary across Europe are hitherto lacking. We analysed recoveries of Water Rails ringed in Europe and tested for a general migration direction in this material. From previous literature descriptions we predicted birds to migrate farther the longer north and east they breed. More than half of the birds included in the data set were ringed in Germany (48%) and Hungary (12%) and most winter recoveries came from SW coastal Europe. We found that the migratory direction in autumn was strongly oriented towards SW with no effect of latitude or longitude of the breeding site. There were no differences in migration direction between old (2Y+) and young (1Y) birds, or between males and females, although sample sizes were admittedly small in the latter comparison. As predicted, migration distances were positively correlated with both latitude and longitude of breeding sites. We encourage more trapping and ringing of Water Rails breeding and wintering across Europe in order to improve the ring recovery data. The use of modern tracking devices like light-level geolocators also has a high potential of improving our understanding of migratory ecology in this secretive species.
Highlights
Bird migration is often divided into two main classes (Terrill & Able 1988, Alerstam 1990, Berthold 2001, Newton 2008): 1) facultative migration where movements are typically irregularly induced by exogenous factors, and 2) obligate migration which is controlled by endogenous factors resulting in a regular annual movement between the breeding and non-breeding sites
Migration is reported to go along axes in both the east-west and north-south directions in western parts of Europe (De Kroon 1984) but as far as we are aware no analyses have yet statistically evaluated the geographical variation in migration directions and migration distances
Our quantitative analyses of ring recoveries in European Water Rails considerably increase our knowledge about movements in this species
Summary
Bird migration is often divided into two main classes (Terrill & Able 1988, Alerstam 1990, Berthold 2001, Newton 2008): 1) facultative migration where movements are typically irregularly induced by exogenous factors (e.g. food availability and climate), and 2) obligate migration which is controlled by endogenous factors resulting in a regular annual movement between the breeding and non-breeding sites. Migration in many species is readily classified according to this broad categorisation, some species show a considerable variation in migratory behaviour among populations. In the Water Rail Rallus aquaticus migration patterns are known to differ among European populations (Flegg & Glue 1973, Cramp & Simmons 1980, De Kroon 1984, Taylor & van Perlo 1998). According to Cramp and Simmons (1980) birds from the Atlantic and Mediterranean coasts are mainly sedentary, populations east and north of these areas are to some degree migratory and birds breeding east of approx. Migration is reported to go along axes in both the east-west and north-south directions in western parts of Europe (De Kroon 1984) but as far as we are aware no analyses have yet statistically evaluated the geographical variation in migration directions and migration distances
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