From 2005 to 2011, 34 adult Montagu’s Harriers (Circus pygargus) were fitted with satellite transmitters in three different subpopulations in northern Europe by the Dutch Montagu’s Harrier Foundation.
This is the first study to describe in great details the migration system of a Palaearctic-African long-distance migrant. The results of this unique long-term and large scale satellite tracking project were recently published in the Proceedings of the Royal Society B:
Trierweiler, C., Klaassen, R. H. G., Drent, R. H., Exo, K.-M., Komdeur, J., Bairlein, F., & Koks, B. J. (2014). Migratory connectivity and population-specific migration routes in a long-distance migratory bird. Proc. R. Soc. B 281: 20132897. doi: 10.1098/rspb.2013.2897 (free access)
PDF also available from the University of Groningen
The study discovered a previously unknown major stopover area in northwest Africa (northeastern Morocco and northern Algeria, figure 3). This area is used extensively both in autumn and spring, predominantly by birds travelling via the western route (i.e. birds from The Netherlands, western Germany and Denmark). In autumn, Montagu’s Harriers made a large number of lengthy stopovers in these northwest African sites. In autumn, 25% of all stopovers were located in northern Africa, whereas in spring 45% of all stopovers were located in this region. Furthermore, in autumn 46% of all individuals made a stopover, whereas in spring 88% of the birds stopped in this region.
This study shows once more that for effective conservation of migratory animals, key stopover sites (where these animals spent a good amount of time both in spring and autumn) need the same attention as the final destinations of the journey (breeding and wintering areas).