Last year a Leipzig based birder pointed me at two warblers with atypical songs.
So we went out to make some sound recordings for documentation purposes.
We identified them phenotypically as Blackcap Sylvia atricapilla and Garden
Warbler Sylvia borin.
070624, Eurasian Blackcap Sylvia atricapilla, atypical song, Torgau, Germany
070624, Garden Warbler Sylvia borin, atypical song, Torgau, Germany
For more documented cases like this, please look at the following website: Raetselsaenger