Global study finds human noise disrupts bird behaviour and breeding
Global meta-analysis of 160 studies finds traffic, aircraft and industrial noise disrupt communication, increase stress and reduce reproductive success
A global picture of a growing problem
Anthropogenic noise - from roads, aircraft, industry and urban development - is having widespread and measurable effects on birds, according to a major new global study published in Proceedings of the Royal Society B. Drawing together results from 160 studies and 944 effect sizes across 161 species on six continents, researchers found consistent impacts on behaviour, physiology and breeding success.
While the idea that birds struggle to sing over traffic noise is well established, this meta-analysis shows the problem runs far deeper. Noise pollution affects how birds communicate, forage, assess risk, use habitat and ultimately how successfully they reproduce.
Clear impacts on behaviour and stress
The strongest and most consistent effects were seen in communication, vigilance and foraging behaviour. Birds exposed to human-made noise altered their songs, changed how much time they spent scanning for danger and adjusted feeding behaviour. Aggressive interactions were also affected.
Physiological changes were recorded as well. Many studies measured stress-related hormones, and the meta-analysis found clear shifts in hormone concentrations under noisy conditions. Both increases and decreases in stress hormones can have negative consequences for immune function, metabolism and overall condition.
Breeding success takes a hit
Perhaps most concerning was the overall negative effect of anthropogenic noise on reproduction. Across studies spanning pairing success, egg survival, clutch size and fledging success, the pattern pointed towards reduced breeding performance in noisy environments.
The authors note that communication underpins much of the breeding cycle. If songs used in mate attraction are masked or altered, if alarm calls are harder to detect, or if nestling begging calls are not heard clearly, reproductive success can suffer at multiple stages.
Not all birds respond in the same way
Importantly, the study did not treat birds as a single group. The researchers examined how ecological and life-history traits influenced vulnerability.
Species nesting nearer the ground experienced stronger negative reproductive effects. Birds using open nests showed stronger growth responses than cavity nesters. Habitat also mattered: species living in deciduous forests and grasslands tended to show weaker physiological responses than habitat generalists, suggesting that vegetation structure may help buffer noise.
Some traits appeared to offer partial protection. Species with longer songs and omnivorous diets showed weaker growth-related impacts, possibly because dietary flexibility and signal structure provide resilience in disturbed environments.
Habitat shifts and wider ecological consequences
Noise also influenced habitat use. Birds nesting higher in the canopy tended to show smaller responses, supporting the idea that tree cover can attenuate sound. Conversely, species using open cup nests exhibited stronger habitat shifts under noise exposure.
Changes in habitat use can trigger knock-on ecological effects - altering competition, predator exposure and community structure. Yet the authors note that most research to date has focused on a relatively small number of bird families, meaning much global diversity remains understudied.
An underappreciated conservation pressure
The study highlights anthropogenic noise as a pervasive but still under-recognised conservation issue. Unlike habitat loss or climate change, noise pollution does not always leave visible traces - but its biological effects are measurable and, in some cases, substantial.
The findings underline the need for noise mitigation to be considered in planning, infrastructure development and land management. From road placement and flight paths to industrial siting and urban design, reducing chronic noise exposure may be critical for maintaining healthy bird populations in human-dominated landscapes.
As the authors conclude, the long-term population and community-level consequences of noise remain insufficiently studied. But the evidence is now clear that human sound is not just background - it is an ecological force shaping how birds live and breed.
The study frames this as a case for meaningful collaboration between knowledge systems, especially when global biodiversity monitoring is patchy and many declines - particularly local extinctions - go unrecorded by formal science. In that sense, the research is as much about how we know what is happening to birds as it is about what is happening.
What to take from it - and what not to
This is not a study about individual birds losing weight, and it is not a direct measurement of body size trends within species. It is about which species remain common, which fade, and what that does to the “average” body mass of the birds that people most often encounter in their home landscapes.
That distinction matters, because it points to a quiet form of ecological erosion. You do not need a silent spring for change to be real. Sometimes the warning is that the big birds - the geese, cranes, curassows, guans, large raptors, and other heavier-bodied species - are no longer part of the everyday fabric of life, replaced by smaller birds that can hang on in altered habitats.
The wider message - a thinning of ecological richness
Taken together, the findings add weight to the idea that the avian extinction crisis is not only visible in global datasets and formal monitoring schemes. It is also being registered in the memories and observations of communities who have lived with the same landscapes for generations.
And perhaps that is the most powerful message here - that biodiversity loss is not just a scientific graph or a policy target. It is experienced as a change in what is normal: what flies overhead, what calls from the trees, what is still common enough to be named without thinking - and what is no longer there to be named at all.
February 2026
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