Individual variation in migration tracks of Arctic Terns (continuation)

This project wants to determine the effect of climate warming, wind, weather and El Nino on the migration route and timing of Arctic terns from Svalbard. Using geolocators,we have successfully established 36 tracks of arctic terns migrating from Svalbard to Antarctica and back. 66 terns with geolocators have not been caught yet. When re-caught, we want to replace the geolocator, to study individual consistency in route and timing. As last winter had an exceptional intense El Nino effect, it is important to collect also tracks in the next year to compare variation within the same individual. We want to use colour rings to be able to identify individuals in the field. There is general concern (Arctic Council-CAFF-CBIRD group) about a population decline in Arctic terns. It is unknown if bottle necks exist within the Arctic breeding ground or during migration. Arctic tern tracks can alo be used to indicate hot spots of non commercial small fish in the Atlantic Ocean. We want to re-equip 20 birds with earlier tracks with new geolocators. All other birds with geolocators or their partners will receive an individual coded plastic ring to support identification in the field. We are reducing the number of geolocators but also refine the experiment by marking experimental birds after the experiment and their partners with individual colour rings.