Migration patterns of Eurasian Curlews (Numenius arquata)

Contact:

Dr. Philipp Schwemmer, Prof. Dr. Stefan Garthe

Partners:

- University of La Rochelle (Pierrick Bocher & Jerome Fort)
- University of Tartu and Ornithological Society of Estonia (Jaanus Elts & Riho Marja)
- Federal Agency for Nature Conservation

Project description:

The Wadden Sea is an important resting site on the East Atlantic Flyway for Eurasian Curlews (Numenius arquata). However, there is currently little information regarding the connectivity between breeding, staging and over-wintering sites. Furthermore, it is not sufficiently known how strong migration routes of Curlews overlap with offshore wind farm sites. Therefore, we have been catching about 20 Curlews at high tide roosts along the German Wadden Sea Coast since 2013. All individuals were equipped with GPS-GSM dataloggers. The devices recorded the migration routes in intervals of up to 5 minutes allowing to assess detailed information on the temporal patterns of migration. Finally, using GPS dataloggers, it is possible to collect valid data on flight heights. This enables to assess the potential collision risk with offshore wind turbines.

Preliminary results:

Curlews left the Wadden Sea mainly during April and migrated to their breeding grounds that were located exclusively in northwest Russia only within two to four days. All individuals remained in the breeding area for 50 to 70 days, and then returned to the same place in the Wadden Sea where they had been caught. 
Curlews showed a characteristic broad front migration without the use of flight corridors e.g. along the coasts. Some individuals migrated in close vicinity to operating offshore wind farms in the Baltic Sea. Flight heights varied profoundly between several hundred and a few meters over ground. A high proportion of migration time was recorded in rotor heights of offshore wind turbines.
Only single individuals migrated further south during winter, whereas the main proportion of curlews overwintered in the Wadden Sea. Foraging on the intertidal mud flats, Curlews showed a high site fidelity and mostly preferred muddy areas with high densities of polychaetes. 
 

Curlew Dunlin Wadden Sea

Fig.1: Curlew and dunlins foraging on characteristic muddy intertidal flats (Photo: F. Güpner).

 

Eurasian Curlews

Fig. 2: Setting up a mistnet in the Wadden Seat to catch Eurasian Curlews (Photo: J. van Gils).

 

Eurasian Curlews Map

Fig. 3: Migration route of an Eurasian Curlew in three consecutive years. The breeding area is located at the White Sea. The Curlew exclusively used the Wadden Sea outside the breeding time. 
Base map: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroGRID, IGN, and the GIS User Community