A new exploratory approach to the study of the spatio-temporal distribution of ring recoveries: the example of Teal (Anas crecca) ringed in Camargue, Southern France

We use a new method called product kernel estimator to explore the spatial and temporal distribution of 9,114 recoveries of Teal (Anas crecca) ringed in Camargue, southern France, and recovered over the whole of Europe. This method allows exploration of the changes in time of the probability density to recover a ringed bird over a grid covering the study area. We thus identified two migration corridors for this species to the north and south of the Alps, whereas earlier analyses mostly suggested a southern route from Camargue, especially in spring. The northern route seems to be used to a greater extent in autumn than in spring, indicating a frequent abmigration (animals switching from one corridor to the other). Moreover, migration of the population seems faster in spring than in autumn. The simultaneous presence of Teal recoveries in many distinct geographical areas in spring is consistent with the idea that these ducks are not limited by their migratory speed in spring, nor do they wait until favorable environmental conditions before colonizing their breeding areas.