I'm sure we all know the frustration, trying to talk to someone in a loud area and constantly screaming, "What did you say?! Can you repeat that??" Most times people either have to shout louder, or just have the conversation later in a quieter area. Believe it or not, our fellow wildlife deals with the same problems. Only, they figured out a permanent solution for dealing with the issue.
It has been shown that there is a strong link between the change in song and the change in noise, in the sparrows of San Fransisco's Presidio district. The current study being done tracks bird songs from as far back as 1969 up until current day. Researchers also know how San Fransisco's streets have become much noisier based on studies done in 1974 and 2008. The quiet areas that these birds once lived in are now filled with noise pollution. The sparrows in return, have made themselves louder. The birds used to have a low hum which would work, until a car came along and covered up the sound. Now they have one primary high-range dialect. The birds have adapted because these songs are their form of communication. It is how the attract mates, as well as warn each other of predators. When these calls can't be heard, the sparrows start running into trouble. Compared to the calls recorded in 1969, the calls of today are not only louder but they sound more threatening. These birds are much more defensive, which is understandable due to their current surrounds. A lot of animals have a hard time surviving when rural areas become cities, but this is just another example of natural selection at its finest.