International study involving Czech scientists shows bird songs have become quieter and less varied

Natural sounds, and bird song in particular, play a key role in building and maintaining our connection with nature. A new international study, involving Czech scientists, reveals that bird choruses across Europe and North America are becoming quieter and less varied, due to widespread decline in bird populations.

The study, published in the Nature Communications magazine, has combined citizen science bird monitoring data with recordings of individual species in the wild to reconstruct how the soundscapes have changed over the last 25 years across Europe and North America.

The international team of researchers was headed by Dr Simon Butler from the University of East Anglia in Norwich:

Photo: LSC,  Pixabay,  CC0 1.0 DEED

“We have these amazing long-term monitoring data collected by citizen scientists from sites right across North America and Europe, so we had access to data from every 200,000 sites that are visited annually. People go there and count which species they see and hear and record the number of individual birds.

“We took those data and combined it with sound recordings for each species and layered up recordings of individual species according to how many individuals were detected during the survey.

“That way, we created a composite soundscape to reflect what it would have sounded like had you been standing next to the person who was doing the count at the time. And then we could analyse the acoustic patterns within those soundscapes.”

The result of the analysis revealed that as the number of individuals and species decline, the sounds generally becomes less diverse and less intense because there are fewer individuals providing acoustic energy into the soundscape.

Petr Voříšek, head of the Czech Ornithological Society, who was responsible for analysing the European data, says that fortunately, the situation in the Czech Republic is not as bad as elsewhere in Europe:

Petr Voříšek | Photo: Czech Television

“In the case of the Czech Republic, there are quite a few localities where the overall observed decline in acoustic diversity and loudness of spring birdsong is not so pronounced, there are even localities where it went in the opposite direction.

“I've seen a decline in reconstructed birdsong at a site where I've been counting regularly since the mid-90s, and there, those characteristics are actually improving.”

One of the reasons Czech soundscape is richer than the EU average are the rising numbers of starlings. Overall, however, bird populations are dwindling with alarming speed both in the Czech Republic and elsewhere in Europe. That can have a negative impact not only on the ecosystem but also on people’s mental health, says Simon Butler:

“Bird song and our relationship with the environment are really closely entwined. It is embedded in our culture. In more recent times, over the past 18 months, lots of us have drawn comfort from spending time in nature and enjoying benefits to our mental health and well-being.

“We know that birdsongs are a key component of assessing the quality of our nature experience. How we perceive the quality of that is impacted by the quality of the soundscape. So as we lose the acoustic diversity and intensity, the likelihood is that the benefits that we can get will be declining.”

Authors: Ruth Fraňková , Ondřej Ševčík