The iconic call is a sharp, shrill screaming "srriiiih" or "sviiir" that carries loud and far. It is delivered above all during the evening rushes, when groups of non-breeding birds chase one another at high speed around rooftops and church towers — one of summer's most characteristic sounds in Swedish towns. Breeding birds are quiet inside the crevices; it is above all the sociable flocks out in the open that scream.