Despite its tiny size, the Eurasian Wren has one of the most powerful songs of any bird in the Swedish fauna relative to its body weight. The song is an explosive, trilling burst of rapid warbles and clear whistles that lasts around five seconds and carries for several hundred metres. It sings freely from January to June but peaks in March and April, when the male is defending his territory. It is heard at its best in the early morning along woodland edges and forest tracks with brush piles and upturned root plates. The commonest alarm call is a hard, clicking rattle, "tek-tek-tek", that sounds like two sticks being knocked together and is given persistently when the bird is disturbed.