Is the dawn chorus getting louder and if so, why?

Is the dawn chorus getting louder and if so, why?

Starlings at the West Pier, Brighton (before the fire) Photo: Mark Ware

On the 23rd April 2015, The New Statesman published an online article about investigations that appear to suggest that the dawn chorus is getting louder. If that is the case, why could it be? The article asked, ‘is this sort of thing simply our current dry weather conditions rendering all sound intense, or a more profound species change?’

Our Wavelength Project recordings of natural sounds, including birdsong, began at Kent Wildlife Trust earlier this year. We then went on to include recordings of man-made sounds, such as traffic noise, building construction sites, etc. We have been measuring the decibel levels of all recorded natural and man-made sounds for comparison purposes. Through this process, we have discovered that in urban environments the majority of the artificial sounds we’ve recorded have a higher decibel level than that of the majority of bird calls.

Is this significant in relation to the question, ‘Is the dawn chorus getting louder?’ To help answer that question, it is important to understand why birds sing. They sing for a variety of reasons including claiming and defending territory, attracting a mate and general communication. If birds are calling in environments where artificial noise has a higher decibel level than their bird calls, logic would suggest that the only way for them to overcome this problem is to sing louder or adapt their singing in other ways in order to communicate. If this is so, there may be unfortunate  consequences. It is understood that when birds sing, they use up a lot of energy. For birds that need to sing louder and are able to do so, their efforts may create health risks for them because of the valuable extra energy required to make louder calls.

As part of the Wavelength Project we will be consulting with Dr Alex Woodcock, former stonemason at Exeter Cathedral, archaeologist and author who has a specialist interest in the medieval period. Our aim is to create a soundscape that will be a faithful representation of the types of soundscapes heard in medieval England. When discussing which sounds heard today would have been heard in medieval times, we initially assumed that birdsong would have been one of those sounds. But following our recent sound and decibel recordings, we are beginning to question that assumption. Man-made sound pollution has steadily and dramatically increased since the Industrial Revolution. As a result, natural sounds including birdsong are often not clearly audible, especially in urban environments where the addition of man-made buildings also affects the travel of sound.

Can birds adapt to noise pollution and buildings that obscure their birdsong? We don’t have enough information to say. Research would have to take into account other factors in addition to decibel levels, including the measurement and comparison of the sound frequency components of man-made sounds and bird calls. But our early findings suggest that this is a topic worth investigating if we want to preserve and protect wildlife and birdsong.