I’m sure you have noticed just how loud cities and their surrounding suburbs are getting. Well, just as the noise annoys you sometimes, it is also annoying our fellow bird populations.
How? I’m glad you asked.
All organisms have these things we call sensory systems. They use them to navigate through their everyday lives. Humans depend on their sense of vision, hearing, touch, taste and smell on a daily basis to survive and navigate in their environments. Birds, however, depend mostly on their hearing to survive. I know everyone has heard a bird sing before. Birds sing to attract mates and for communication, not to impress judges on America’s Got Talent. They also use their hearing to protect themselves from predation and to protect their habitat. So, what happens when they can’t hear? Well, what do you do when one of your senses is taken away or impaired? First, you would probably panic, but then you would calm down and realize that you’re going to have to change your behavior if you want to survive.
That’s EXACTLY what some bird populations are doing. I would like to use Great tits (Parus major) as an example. Great tits are a beautiful species of bird that are widespread and common throughout North and Central Asia, Europe and the Middle East.
But first, I would like to explain why city noise, or ‘anthropogenic noise’, is so bothersome and how it affects communication. Anthropogenic noise is just a fancy way to say noise that is caused by humans (i.e. cars, trains, airplanes, etc). I’m sure you have experienced the frustration of going on a long drive and not being able to listen to your favorite radio station the entire time. At some point, your station starts to go in and out and then another station takes over. That’s because those stations were being broadcasted on the same frequency. It caused a disturbance. Now, as we all know, communication is a two-way street. There has to be a signal and that signal must travel and be received. In this case, the signal is the bird’s song and the receiver is the bird. Noise is defined as anything that masks or disrupts a signal. If the signal of the bird’s song can be masked and/or disrupted by anthropogenic noise.
This is what happens to birds in urban areas. The songs they sing have similar frequencies to the urban noise around them, so then their fellow birds in the community have trouble hearing them sing. In the case of the Great tit, they were found to have changed the frequency of their songs in response to the urban noise. Urban noise usually has a low frequency. In a study conducted by Mockford and Marshall (2009), the songs of Great tits that lived in urban areas with lower background noise (not a lot of noise pollution) had lower minimum frequencies than those that lived in urban areas with higher background noise (a lot of noise pollution). Great tits have also been found to shorten the first note of their songs in addition to changing the frequency (Slabbekoorn and den Boer-Visser, 2006). As you can see, Great tits put in a lot of work trying to make it so that their songs will not be masked by low-pitched urban noise.
Now, as the caring human being that I know you are, I bet you are wondering what is being done to help these birds and many other bird populations dealing with the same problem. Slabbekoorn and Ripmeester (2007) have suggested that building noise barriers between noise sources and bird habitats can allow for less urban noise to reach the breeding habitats of these birds. Solid concrete walls and walls made of vegetation could suffice as noise barriers for birds. You wouldn’t be able to build a concrete wall yourself, but maybe start taking part in your community garden or park. Help build some suitable habitats for your community bird population. ?
For additional information on Great tits:
https://www.rspb.org.uk/birds-and-wildlife/bird-and-wildlife-guides/bird-a-z/g/greattit/
http://www.garden-birds.co.uk/birds/greattit.htm
Works Cited:
Mockford EJ, Marshall RC (2009) Effects of urban noise on song and response behaviour in great tits. Proc R Soc Lond B Biol Sci 276: 2979–2985.
Slabbekoorn H, den Boer-Visser A (2006) Cities change the songs of birds. Curr Biol 16: 2326–2331.
Slabbekoorn H, Ripmeester EA (2008) Birdsong and anthropogenic noise: implications and applications for conservation. Mol Ecol 17: 72–83.
Pictures:
https://phys.org/news/2015-11-great-tit-bird-due-exposure.html
http://www.wnyc.org/story/225039-whats-nycs-most-annoying-sound/