Secret wintering grounds of Europe's rarest migrant songbird discovered

After five years of searching, an expedition team has finally located the wintering grounds of the Aquatic Warbler in Senegal. The species is Europe’s most endangered migratory songbird, and its whereabouts in the winter months have long remained a mystery.

Co-ordinated by Birdlife International’s Aquatic Warbler Conservation Team (AWCT), the RSPB and the French organisation Bretagne Vivante, the search party located significant numbers of Aquatic Warblers in a region of some 100 sq kms within the boundaries of the Djoudj National Park, an important bird area in the north-west of the country.

Feathers from Aquatic Warblers trapped in Europe were analysed to help refine the search area. Aware that the feathers would have grown on the wintering grounds in Africa, the research team looked for isotope patterns and then compared the results with isotope maps of West Africa.

The results from this analysis showed that the birds were wintering at sites just south of the Sahara, and a closer look at the sparse African records, alongside computer modelling of possible suitable climatic conditions, led the researchers to likely areas along the Senegal River.

AWCT Chairman Martin Flade commented: “Thankfully, substantial parts of the bird’s wintering range fall within protected areas, with the Djoudj National Park alone possibly holding up to a third of the world population.”

Aquatic Warblers breed as far west in Europe as Poland and Hungary, but the population is declining and knowledge of the species in its winter range, as well as on the breeding grounds, is crucial to its conservation. Interestingly, it occurs regularly in small numbers in south-west England and Brittany on migration in autumn to its wintering areas, but not in spring, suggesting a different route back to Europe.

Photo: Steve Young.