Herkunft und Zugverhalten von in der Schweiz überwinternden oder durchziehenden Tafelenten Aythya ferina

– We ana-lysed 2473 ringing recoveries of Pochards ringed or recovered in Switzerland. The following questions were addressed: Where are Pochards that winter in Switzerland to be found during the rest of the year? Does mig-ration behaviour differ between sex and age classes? Are there subpopulations within Europe? Has there been a change in migration patterns over the last decades? How fast do Pochards migrate? Pochards ringed (or recovered) in Switzerland have been recovered (or ringed) in southern France, central and eastern Europe and eastward to the lowlands of western Siberia. During the breeding season, recoveries concentrate in the Russian-Kazakh steppe. In winter Pochards are recovered mostly in western and central Europe. Winter movements from Switzerland to the Po valley, to southern France and in a northwestern direc-tion are observed regularly. Spring migration takes place in March. Males in spring depart earlier than females and return later in autumn. From April to June, the mean recovery locations of females lie only about half-way between Switzerland and the mean recovery locations of males. From July to September, the average recove-ry location does not differ between the sexes. The females move to WSW in October, and the males follow in November. The females seem to perform a leap frog migration, i.e. females breeding in the north-east winter further south-west than females breeding in central Europe. This leap frog pattern could also explain why the mean locations of the sexes during summer are different: If Russian females only migrate through Swit-zerland but do not winter here, fewer of these birds will be caught and, consequently, fewer are recovered in Russia. At the same time, central European females are caught more regularly, giving more breeding records from central Europe, which pulls the mean summer recovery location of females to the west. We suggest not dividing Pochards wintering in Europe into subpopulations: (1) Recoveries of Pochards rin-ged in Switzerland stem from the entire area of winter distribution of Pochards in Europe. (2) Strong and Eu-rope-wide movements are taking place within winter. (3) The breeding distribution of Pochards wintering in Switzerland is congruent with the breeding distribution of Pochards wintering in Great Britain. The breeding distribution of Pochards wintering in Europe overlaps with the breeding area of Pochards wintering in India, while very few individuals ever seem to change between the two winter populations. Nothing, however, is known about a genetic exchange between the two winter populations. The timing of spring migration of males advanced by 20 days since the 1970s. This might be due to a combination of increasing recovery probability in Russia and an earlier spring migration. We did not find any change in timing in spring or autumn migration in females and in autumn migration in males. Distances up to 1000 km can be covered in two or three days. For longer flights, Pochards seem to travel with 70 km/d.Key words: Migration, spatio-temporal analysis, ringing recoveries, flyways,