This study tested the hypothesis that the song of male birds can funct
ion to attract mates. At 11 different locations on our Wyoming study a
rea, we broadcast the song of male house wrens (Troglodytes aedon) fro
m a loudspeaker mounted next to an empty nest box in an unoccupied wre
n territory. The number of female wrens attracted to the 'speaker box'
was compared to the number visiting a silent, control box on another,
unoccupied territory nearby. Females visited speaker boxes at a signi
ficantly higher rate than they visited control boxes. Ten females visi
ted speaker boxes in six different trials during periods when no male
was associated with either the speaker or control box (total time = 45
.5 h; visit rate = 0.22/h). In contrast, only one female visited a con
trol box during these same periods (= 0.02 visits/h), and she did so a
fter first visiting the speaker box. Two females visited the speaker b
ox simultaneously in some trials and chasing or fighting always ensued
. Many females showed signs of settling permanently at speaker boxes,
remaining at speaker boxes from their arrival to the end of the trial
(> 5 h in two cases), and most began constructing nests in boxes, desp
ite the absence of a male. In summary, this study provides strong expe
rimental evidence that the song of male house wrens can function to at
tract mates for breeding.