This is a video of a corncrake, including its call.
From the Dutch ornithologists of SOVON:
Good year for the corncrake
Halfway in June, already almost 150 calling corncrakes had been spotted in our country. For a time it looked as if this species after the big numbers in 2003 was on its way down. However, this season already at the end of April the first calling males had been heard (usually, in early May). The biggest numbers now are in the fields of the Oldambt in Groningen province, and in meadows along the IJssel and Zwarte Water rivers around Zwolle.
A video on radio transmitters on corncrakes for research is here.
More about corncrakes in the Netherlands is here.
UK: Corncrakes suffer severe decline after grant reforms for farmers: here.
2009: UK corncrake numbers looking good – Please help the survey: here.
Scottish corncrakes under threat from EU agricultural policy: here.