Bird migration in space and time: chain migration by Eurasian curlew (Numenius arquata arquata) along the East Atlantic Flyway

Migration patterns in birds vary in space and time. Spatial patterns include chain, leap frog, and telescopic migration. Temporal patterns such as migration duration, number and duration of stopovers may vary according to breeding latitude, sex and season. This study aimed to verify these patterns in a long-distance migrant, the Eurasian curlew (Numenius arquata arquata), and to provide a synopsis of spatio-temporal migration patterns in this species of concern throughout the East Atlantic Flyway. We tagged 85 adults with GPS-data loggers in Germany, Poland, France, and Estonia between 2013 and 2019. We computed the distance flown, linear loxodromic distance, duration, stopover number, total stopover duration, mean stopover duration, departure time, and arrival time for 177 out of 187 tracks. On average (± standard deviation), spring migration occurred from April 4–14 (10.2 ± 8.4 days), curlews flew 3,623 ± 1,366 km, and had 5.8 ± 3.6 stopovers, with a duration of 29.4 ± 38.2 h per stopover, while autumn migration occurred from June 18–29 (10.9 ± 9.9 days), curlews flew 3,362 ± 1,351 km, and had 5.4 ± 4.0 stopovers, with 31.8 ± 32.3 h per stopover. Curlews displayed chain migration, because wintering curlews maintained the latitudinal sequence to their breeding sites. Southern curlews had a longer nesting period due to their earlier arrivals. While spring arrival at breeding sites did not differ between the sexes, in autumn females departed earlier than males. Migration duration and distance, as well as stopover number and duration showed a significant increase with breeding site latitude but did not differ between the sexes or between spring and autumn migrations, suggesting that curlews took a comparable amount of time migrating during both seasons. The high site faithfulness in curlews suggests that rapid autumn migration allows them to return to defend their winter foraging areas.Funding provided by: Bundesamt für NaturschutzCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100010415Award Number: project "Birdmove" (FKZ 3515822100)Funding provided by: Bayerisches Landesamt für UmweltCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100015607Award Number: Funding provided by: Estonian Environmental Investment Centre*Crossref Funder Registry ID: Award Number: Funding provided by: ECONAT project funded by the Contrat de Plan Etat-Région*Crossref Funder Registry ID: Award Number: Funding provided by: CNRSCrossref Funder Registry ID: http://dx.doi.org/10.13039/100012681Award Number: Funding provided by: European Regional Development FundCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100008530Award Number: Funding provided by: Ligue pour la Protection des Oiseaux*Crossref Funder Registry ID: Award Number: Funding provided by: EU Cohesion Fund under the Operational Program Infrastructure and Environment 2014-2020, under the project POIS.02.04.00-00-0019/16 entitled "Implementation of the National Action Plan for Eurasian Curlew - stage I" (http://ochronakulika.pl/), coordinated by the Wildlife Society "Stork"*Crossref Funder Registry ID: Award Number: Funding provided by: Bundesamt für NaturschutzCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100010415Award Number: project "Trackbird" (FKZ 3519861400)Funding provided by: Bayerischer Naturschutzfond*Crossref Funder Registry ID: Award Number