Asked by: Roger Collison, Holmfirth
Male birds use their songs to advertise for mates and to warn rival males away from the territory they control. Natural selection favours birds that can broadcast over a wider area and so they have evolved powerful diaphragm muscles.
But they use other strategies to make themselves heard as well. Research at the University of St Andrews has found that as the background noise from traffic gets louder, birds sing at higher frequencies, which aren’t affected so much by the low rumble of passing lorries. And robins in cities sing more at night time too, to avoid the rush hour noise.