This is a video of a singing aquatic warbler at Nagyivan, Hortobagyi National Park, Hungary.
From Wildlife Extra:
Aquatic warbler visits east London
The aquatic warbler is a rare UK visitor, occasionally dropping in on its unusual migration route between Eastern Europe and West Africa. These small brown and black birds are difficult to spot, but a one has been positively identified in a reedbed near the RSPB Visitor Centre. It’s only the third time since records began that an aquatic warbler has been spotted at Rainham Marshes. The last time was in August 2004.
Aquatic warblers don’t spend much time in the UK so there’s not much that can be done to help them here. Instead, the RSPB has invested time, energy and money in supporting our International colleagues in conserving and enhancing the species’ strongholds, particularly in Poland.
Winter in Senegal
Scientists recently made a major breakthrough in efforts to save aquatic warblers. No one knew where the birds spent their winters and they’re too small to tag electronically. Samples of feathers were analysed and scientists were able to measure isotopes from winter feather growth to narrow the global search for their winter breeding grounds. This allowed researchers to focus their efforts on western Africa and the secret breeding grounds in Senegal were discovered.
Aquatic warbler facts
1. The aquatic warbler breeds in Belarus, Germany, Hungary, Lithuania, Poland, Russia and Ukraine (its main populations are found in Belarus, Hungary, Poland and Ukraine).
2. Its global population is estimated at between 12,500 and 19,900 singing males, which include 50 to 500 singing males outside Europe in western Siberia. Around 5,000 to 15,000 aquatic warblers winter in Djoudj National Park in north-western Senegal, that is approximately 60 % of the global population. Work is underway to ensure their needs are met while the search continues for other secret breeding grounds.
3. The aquatic warbler’s favoured habitat is large open sedge and Cladium fen mires. It has suffered a severe decline because much of this habitat has been lost in western and central Europe.