Background The aquatic warbler (Acrocephalus paludicola) is Europe’s rarest migratory songbird and a globally threatened species (listed as ‘vulnerable’ by the IUCN and included in Annex I of the EU Birds Directive). It has very specific habitat requirements, being found only on fen mires or wet meadows on peaty soil covered by sedges. The water level must be above ground, but not by more than 10-15 cm, to avoid flooding the nest. Aquatic warblers do not form pairs; both sexes mate with a large number of partners – one brood may have up to five fathers. While the male spends the entire breeding season attempting to attract females with his evening song, the female raises the young alone. This makes the quality of habitat vital, since survival is dependent upon availability of an exceptional quantity of insects. Once widespread and numerous on fen mires and wet meadows, the aquatic warbler has suffered from habitat loss and degradation. With its habitats now dependent on human land-use and extremely susceptible to land-use changes, it is effectively a conservation-dependent species. More than 10 000 of the estimated global population of some 17 000 pairs are found in Belarus, with other major breeding populations in Poland and Ukraine. There is a small aquatic warbler breeding population in Lithuania (c. 100 pairs), principally located in the Neman river delta. Conservation and maintenance of aquatic warbler populations in a stable state on Lithuanian territory, which is situated on the periphery of the main distribution range, is not possible without maintenance of the stable high number of species populations in the centre of the range. The state of the world population of the aquatic warbler is largely determined by the state of its largest key habitat – Zvanets fen mire in Belarus, which supports a breeding population of 2 100 to 4 400 pairs. Objectives The LIFEMagniDucatusAcrola project aims to restore degraded habitats of the aquatic warbler in Lithuania, as well as in parts of Belarus. Reducing fragmentation of aquatic warbler breeding habitats is a major precondition for achieving a long-term favourable conservation status in its north-east European breeding range. Habitats in Lithuania are often key stepping stones connecting the remainder of the EU population (in Poland, Hungary and Germany) with that found in Belarus. The project will apply traditional restoration methods for the target habitats, such as elimination of reeds and removal of bushes and redundant biomass. It will also implement prescribed burning to increase the productivity of the degraded habitat. A second innovation will be the application of an accelerated method of seeding sedge grass vegetation. The project will establish self-sustaining farming mechanisms to ensure long-term socio-economic preconditions for maintaining aquatic warbler breeding habitat in the Neman river delta. Drawing on European best practice, it will also set up a biomass processing facility in this area to create a marketable product and thereby ensure constant demand for late-cut biomass gathered from the surrounded breeding areas of the aquatic warbler. Most notably, the project also aims to carry out the first translocation of aquatic warblers. Expected results: The project expects to achieve the following results: Habitat restoration and improvement actions over an area of 20 509 hectares in Lithuania (Tyrai marsh, Šyša and Sausgalviai polders and Žuvintas marsh) and Belarus (Zvanets mire, Servech mire and Dokudovskoe). This will include actions to optimise the hydrology of fen mire and other wetland habitats; Translocation of 100 aquatic warblers from Zvanets mire in Belarus to Žuvintas Biosphere Reserve in Lithuania, with an expected 40% return rate; Drafting of four site management plans and two species action plans for the aquatic warbler (one for Lithuania; one for Belarus). These will be approved by the competent authorities; Creation of a biomass processing plant in the Neman river delta area; Assessment of the effectiveness of conservation measures for the aquatic warbler in the project areas; and A comprehensive communication campaign aimed at raising public awareness of the importance of aquatic warbler conservation. The effectiveness of the species translocation will be discussed at expert meetings and the project’s closing conference. If successful it is expected that further aquatic warbler translocations will take place in Poland and Hungary.