Its song is described as "a monotonous warbling" and it is probably not the prettiest specimen you can spot. But it is hailed as "a birdwatcher's bird" and there are fewer than 20,000 worldwide.
In a move to save the aquatic warbler, the rarest songbird in Europe, the Royal Society for the Protection of Birds yesterday said it will spend £400,000 to help buy up to 1,000 hectares of the Biebrza marshes in eastern Poland, home to about 2,700 singing males.
This is the first time the RSPB, which owns almost 200 nature reserves in the UK, has bought land outside Britain, and the Biebrza project will be managed by the RSPB's Polish partner, OTOP.
"The Biebrza marshes support 80% of the European Union's population of the globally threatened aquatic warbler," said the RSPB's chief executive, Graham Wynne. "Without using RSPB funds to purchase land, we were concerned that this bird might not have had a secure future in its European stronghold, as its last breeding sites could be lost through the intensification or abandonment of farming."