Because of the decline in bird populations, the natural soundscape of birdsong in North America and Europe has become less audible over 25 years.
An Eurasian wren (Troglodytes trigonotes) singing in Norfolk. UK David Tipling Photo Library/Alamy
Due to decreasing bird populations in North America, Europe and elsewhere, springtime birdsong could be becoming less varied and quieter than it used to be. This is not only bad for biodiversity but also may have an adverse effect on human health.
The benefits of natural soundscapes have been proven to be beneficial for both mental and physical well-being. These soundscapes include the familiar whistles, trills, and caws that birds make.
Simon Butler, University of East Anglia, Norwich, UK and his colleagues compile bird count data from 202.737 sites in North America, and 16.524 sites in Europe. The data was collected between 1996-2018. The data and recordings of 1067 bird species were then used by the team to reconstruct the probable bird soundscape at each site for every calendar year.
The team randomly recorded 25-second clips from the songs of each bird that was spotted at a specific site in a given year and then inserted them into a 5-minute sound file. Random sampling was used to determine the volume of individual birds. This allowed for birds singing at different distances.
It should sound exactly like if you had taken a recorder into the field with the person doing the bird survey.
The researchers analysed the clips using acoustic modeling, which quantified the song's acoustic characteristics including volume and pitch and variation.
The researchers found that there was a marked decline in the intensity and diversity of birdsongs on both continents over 25 years. This means that soundscapes in these areas have become more quiet and less diverse. These results are indicative of widespread declines in bird biodiversity and bird population in North America and Europe during the same time period.
These declines are partly due to massive increases in human activity such as urbanization, poor forestry practices and pollution. Butler says that climate change has also had an impact on the UK's bird distribution.
He says that birds are used to measure biodiversity health. Therefore, declining bird populations could indicate that other groups such as insects and amphibians may be also being affected.
Butler says that spending time in nature can have a number of benefits for your physical and mental well-being, as well as mental health. If our soundscapes change, it could indicate that the quality and benefits of spending time in nature are decreasing.
Journal reference: Nature Communications, DOI: 10.1038/s41467-021-26488-1