This 2017 video is about a great reed warbler singing in Germany.
Great reed warblers used to be not that rare in the Netherlands.
However, they need big reed beds for nesting. And these have often disappeared.
At one spot, grey lag geese fed on the reed making it disappear. In March 2017, a fence was put there preventing geese from eating the reed. Then, the reed started to grow again.
That attracted a great reed warbler couple which built a nest there this spring.