The natural soundscape of birdsong has probably become quieter in Europe and North America over the past 25 years because of a decline in bird numbers
2 November 2021
Springtime birdsong may be becoming quieter and less diverse in North America and Europe due to declining bird populations, which is bad for ecological diversity and may also have a negative impact on human health and well-being.
Natural soundscapes are an important way to connect people with nature, and doing so has been shown to benefit both our physical and mental well-being. The familiar trills, whistles and caws of birds are a major component of these soundscapes.
Simon Butler at the University of East Anglia in Norwich, UK, and his colleagues compiled bird count data from 202,737 sites in North America and 16,524 sites in Europe, collected between 1996 and 2018. The team then used the data and recordings of 1067 bird species taken from an online database to reconstruct the likely bird soundscape that existed at each site for every year.
For each individual bird spotted at a site on a particular year, 25-second clips of their songs were randomly inserted by the team into an empty 5-minute sound file. The volume of individual birds was also randomly sampled to represent birds singing from different distances.
“Ideally, it should sound like had you taken a recorder out into the field as the person was doing the bird survey,” says Butler.
The researchers then analysed the clips with acoustic modelling, which quantified the songs’ acoustic characteristics, including the volume and pitch, and the amount of variation in these properties.
They found a significant decline in the diversity and intensity of birdsongs across both continents over the past 25 years, which means soundscapes in these regions have become quieter and less varied. The results reflect widespread declines in bird populations and biodiversity in North America and Europe over the same period.
Massive increases in human activity, such as agricultural intensification, poor forestry practices, pollution and urbanisation, are partly driving these declines. Climate change has also affected the distribution of birds in the UK, says Butler.
Birds are used as a proxy of wider biodiversity health, so decreasing bird populations indicate that other groups, such as amphibians and insects, may also be dropping, he says.
“Time in nature has a lot of physical and mental benefits to well-being and health,” says Butler. “If the quality of those experiences is declining because our soundscapes are changing, then that suggests the value and the benefits we get from spending time out there might also be deteriorating.”
Journal reference: Nature Communications, DOI: 10.1038/s41467-021-26488-1
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