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Half of Headstarted Eurasian Curlews Explored Beyond Their Main Area Before Migration

Eurasian curlew at Lista, Norway
Conservation · Management

Half of the headstarted Eurasian curlews (Numenius arquata) with suitable GPS data moved outside their main post-release area on exploratory trips before autumn migration. Of 34 birds, 17 made 38 such movements. Twelve birds made exploratory trips away from their main post-release area and later returned, while nine relocated more than 20 kilometres to a new area and stayed there; four of those later relocated again. Relocation distances averaged 71.6 kilometres and reached 220.8 kilometres. The study was published on 24 July 2026 in Journal of Ornithology.

Headstarting involves taking eggs from wild nests, hatching and rearing the chicks under protected conditions, and releasing the juveniles once they are able to fly. The researchers GPS-tagged 62 headstarted curlews released in Poland between 2017 and 2021. Thirty-four provided enough data for the post-release movement analyses, and 20 were tracked continuously from release until autumn migration.

The birds started autumn migration an average of 28.9 days after release. Both their distance from the release site and the distance travelled each day increased during the first weeks and peaked around day 18. For the 20 birds followed throughout the full pre-migration period, the size of the areas they used varied widely. Birds that remained longer before migration, and those released later in the season, tended to use larger areas. The measured habitat and landscape factors did not explain the differences in area size.

The study shows that headstarted curlews do not necessarily stay close to their release site while waiting to migrate. The authors therefore highlight individual variation, timing and the choice of suitable release sites when planning headstarting programmes and monitoring released birds.

Sources and image credit

  1. Obłoza, P., Mirski, P., Krupiński, D., Korniluk, M., Siekiera, J., & Kasprzykowski, Z. (2026). From release to migration: early ranging behaviour of headstarted Eurasian Curlews (Numenius arquata).Primary open-access research article published 24 July 2026. Sixty-two headstarted juvenile Eurasian curlews were GPS-tagged in Poland from 2017 to 2021; 34 were included in post-release movement analyses and 20 provided complete pre-migration tracks. Seventeen of 34 birds made exploratory movements, nine relocated to subsequent post-release areas, and some movements exceeded 200 km. Distance from the release site and daily movement increased during the first weeks after release and peaked around day 18.

Image: Marton Berntsen / Wikimedia Commons — Eurasian curlew (Numenius arquata) in flight at Lista, Norway, photographed 1 September 2026. Representative image of the study species; not a bird from the Polish headstarting project. · CC BY 4.0 — https://creativecommons.org/licenses/by/4.0/ · Source

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