Stage 1: The First-Ever Aquatic Warbler Translocation – A Success Story

Between 2018 and 2019, the world’s first Aquatic Warbler translocation took place. Over two years, one hundred chicks were translocated from the largest known population in Zvaniec Fenmire, Belarus, to a small and rapidly declining population in Žuvintas, Lithuania. This marked a groundbreaking step in conservation, as translocation had never been attempted with this species before.

The results were promising from the start. Out of the hundred chicks moved, ninety-nine were successfully raised and released into Žuvintas. Already in the first year, the success of the method became evident. Bird counts revealed that 22% of the translocated birds returned from wintering in Africa, which is in line with natural return rates reported for other long-distance migrating passerines. Moreover, translocated females were observed successfully raising their own young in Žuvintas, showing that they had fully adapted to their new environment.

In the second year, six (3 males and 3 females) of the translocated birds from the previous year were spotted in Žuvintas, along with three males that had been translocated two years earlier. Following the translocation, the local Aquatic Warbler population reached a historic high. In 2020, Žuvintas recorded the largest population of these rare birds ever observed in the area.

By 2021, three of the translocated males were still present, including one that had been transferred in 2018. Given that Aquatic Warblers live approximately three to four years, this meant that some of the translocated birds had spent nearly their entire lives in Žuvintas, fully integrating into the population. However, by 2022, no translocated birds were found, suggesting that the initial population boost may have gradually declined over time if not fed additionally for a few more years until a stable population was reached.

The experience gained from this first translocation was later published in a scientific article in Animal Conservation, providing valuable insight for future efforts.

🎥 Watch the story of the first stage here:

Stage 2: First Steps to Restore the Almost Extinct Pomeranian Population

Building on the experience of the first stage, conservationists launched a second translocation in 2023–2024, this time in Poland. The objective now is different—not just to test the method, but to begin the full recovery of the nearly extinct Aquatic Warbler population in Western Pomerania, on the border between Poland and Germany.

Over the course of two years, 103 chicks were taken from the vast wetlands of Biebrza National Park and relocated to the restored Rozwarowo Marshes. 83 birds were successfully released into the wild. So far, one season of field monitoring has been conducted revealing 5 returned birds (3 males and 2 females). With another year of monitoring ahead, the team is looking forward to gain a clearer picture of the project’s impact.

While two years will not be enough to achieve full recovery, this translocation marks the beginning of a long-term effort. It is not yet known over how many years a release site needs to be supported to recover a self-sustaining population. Our own modelling results suggest that, translocation must provide birds for several seasons to support the viability of the new population. Based on previous experience with translocation of other passerine birds, each local population to be restored will require translocation over at least 4–5 seasons.

🎥 Watch the story of the second stage here:

Stage 3: Continuing the Effort and Expanding Research

The translocation efforts in the Pomeranian region will continue in the coming years, with birds being introduced on both sides of the Poland-Germany border to ensure long-term population recovery. In Poland, translocations will continue for another three seasons starting in 2025, while in Germany, five translocation seasons are foreseen. Overall, we aim to translocate at least 500 chicks to the Pomeranian population in both countries.

Meanwhile, translocation will also resume in Lithuania at the first-ever translocation site in Žuvintas. This time, the goal will be different: not just to test the method, but to actively restore the population. A new translocation concept will be introduced, where birds will be sourced from the stable but relatively small Aquatic Warbler population in Nemunas Delta, Lithuania. Only nests at risk from early mowing will be used for translocation, making this a unique and carefully targeted conservation effort. Five translocation seasons will be implemented with the target to translocate at least 230 birds in total.

Another translocation will take place in Hungary, where the species has already gone extinct. This will be a one-year translocation with a different focus: to study the migration routes and wintering sites of the Hungarian population. Scientists are still unable to explain the sudden disappearance of several hundred singing males from this region. One leading hypothesis is that something drastic happened along their migration route or at their wintering grounds. By translocating birds and tracking their movements, researchers hope to uncover what caused the population collapse. Therefore, the aim of the pilot translocation of at least 30 Aquatic Warbler chicks to Hungary will be to identify the migration routes and wintering sites. This will be done by attaching geolocators to the translocated chicks and retrieving data once they are recaptured upon return.

In total, at least six Aquatic Warbler populations will be restored by translocating 760 chicks across four countries.

With new projects on the horizon, the next few years will be critical for the survival of the Aquatic Warbler. Conservationists, scientists, and local communities will continue working together to ensure that this rare species has a future.

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The first two stages of Aquatic Warbler translocation was implemented within project LIFE MagniDucatusAcrola, while the third stage will implemented within a new project LIFE4AquaticWarbler. Both projects are financed by EU LIFE Programme and other donors.