Does it seem like the birds in your area are singing louder than they did a few years ago? If you live in an urban area than this very well maybe the case, at least according to a new study by Dr. David Luther from George Mason University.
Dr. Luther studied male white-crowned sparrows in Presidio, San Francisco and he found birds that live in areas with lots of traffic noise actually sing louder. In fact, in comparing sparrow songs that were recorded in 1969 with songs recorded in 2005, they found that they are actually changing their tunes. These birds in 1969 had three distinct dialects, 30 years later they had 2 and now it is only their higher-range song, the song that can be heard over low-frequency ambient noise, that is becoming the preferred song to sing. After all, there’s no point in singing if other birds can’t hear you.
This study can be found in the Journal Animal Behaviour