Eurasian wren
It was once lumped with "Troglodytes hiemalis" of eastern North America and "Troglodytes pacificus" of western North America as the winter wren. The Eurasian wren occurs in Europe and across the Palearctic – including a belt of Asia from northern Iran and Afghanistan across to Japan. It is migratory in only the northern parts of its range. It is also highly polygynous, an unusual mating system for passerines.