The Skylarks War by Hilary McKay Never Judge A Book By Its Cover

Often at that time of year, you could hear skylarks over fields. Soldiers remarked how strange it was that the birds should be there, but in fact the birds had been there for centuries. The really strange thing was that the soldiers were there. Another thing that people thought odd was that the skylarks sang in the language of their homes. In English for the English, in French for the French, and in Dutch for the Dutch. More puzzling still, on the other side of the trenches, a few miles away, the skylarks were singing in German. It was a war where absolutely nothing made sense.