Conserving Aquatic Warbler in Lithuania

Building a Second Aquatic Warbler Population in Southern Lithuania through Translocation

Conserving Aquatic Warbler in Lithuania image

The Bird Conservation Fund (BCF) is teaming up with the Baltic Environmental Forum Lithuania to raise $7,800 to strengthen a second population of Aquatic Warbler in southern Lithuania through a translocation. The proposed grant would underwrite food and dietary supplements for the translocated birds as well as for accommodations for volunteers working in the 2025 season.

The Aquatic warbler (Acrocephalus paludicola) is Europe’s rarest songbird and the only globally threatened passerine bird found in mainland Europe. Over the past century, 95% of its population has been lost, and numbers continue to decline. Currently, the species breeds in only four countries—Belarus, Ukraine, Poland and Lithuania—whereas it once nested in Germany, Latvia, and Hungary. With an estimated global population of just 8,000 singing males , the Aquatic Warbler is the rarest and the only globally threatened passerine bird found in mainland Europe.

The overall project will carry out translocation over five seasons, aiming to relocate at least 230 birds. Two source areas are proposed: the Biebrza marshes in Poland, which host a large population (2,411 singing males), and the Nemunas Delta in Lithuania, where the population is much smaller but stable (200 singing males).
In the Nemunas Delta, an innovative approach will be tested. Nest searches will focus on fields at risk of early mowing by farmers, which could lead to breeding failure. The team will negotiate with farmers to delay mowing until late August. Only nests from fields where mowing cannot be postponed will be collected for translocation. This approach will require intensive fieldwork, but if successful, it could expand the pool of viable source areas and help mainstream the translocation method.
Expected Results of the Translocation in Lithuania:
• Nest searches conducted in the Nemunas Delta.
• Farmers informed about Aquatic warbler nests and encouraged to delay mowing.
• Nests that cannot be saved translocated to Žuvintas.
• Five translocation seasons completed.
• At least 230 birds translocated to Žuvintas.

This project will address key threats to the Aquatic warbler by reducing population fragmentation and increasing genetic diversity. Establishing new breeding populations in Lithuania will create critical "stepping stones," facilitating natural dispersal and strengthening the species' meta-population.