Human presence changes how birds use the landscape
A major GPS-tracking study has found that the physical presence of people can alter how birds and mammals move through the landscape, with effects that cannot be explained by roads, farms and buildings alone.
Birds and mammals are not only responding to the landscapes people have changed - they are also responding to the presence of people themselves.
A new study published in Science has used GPS-tracking data from 37 bird and mammal species across the United States to examine how animals respond to two different forms of human pressure: long-term landscape modification, such as urbanisation, agriculture, transport and energy infrastructure, and the more immediate presence of people.
The researchers combined around 11.8 million animal-tracking locations from 4,581 individuals with mobile-phone data showing daily human presence. This allowed them to separate the effects of people being physically present from the effects of the modified landscapes people have created.
The results show that human presence matters. It was linked to changes in the area or environmental niche used by 67% of mammal species and 68% of bird species studied. More than half of all species were affected by both human presence and landscape modification.
Importantly, these pressures did not always act in simple ways. For many species, the effect of human presence depended on how modified the surrounding landscape already was. In around 60% of species that responded to human activity, the two pressures interacted, meaning that animals often reacted differently to people in relatively natural areas than they did in already heavily altered landscapes.
Among birds, the presence of people reduced the amount of area used by 41% of the species studied. In some cases, birds appeared to restrict their movements when people were present. In others, the response depended strongly on whether the habitat was already modified.
Wild Turkeys, for example, used less space in response to human activity, but reacted less strongly in more modified environments. Great Egrets showed a more complex response, with the direction of their reaction to human presence depending on the degree of landscape modification.
The study also found that human activity could alter the environmental conditions animals used, not just the size of the area they moved through. Sandhill Cranes, for example, showed a different pattern from White-tailed Deer, suggesting that species vary in whether they avoid, tolerate or incorporate human-modified environments into their normal lives.
Common Ravens offered another example of the complexity. The researchers estimated that human activities caused Common Ravens to use around 26 sq km more area per week per animal, while also narrowing their environmental niche by 46%. The authors suggest that such responses may reflect access to human-linked food sources, though they stress that more detailed information would be needed to say exactly what each form of human activity was doing.
Across species that showed significant responses, mammals reduced the area they used by a median of 11% under higher human activity, while birds showed a smaller median reduction of 1.8%. Environmental niche size also tended to contract, though the size and direction of responses varied substantially between species.
The findings suggest that using buildings, roads and farmland as a simple proxy for human pressure can miss an important part of the picture. A quiet road and a busy road may look the same on a habitat map, but they may not mean the same thing to wildlife. Likewise, a protected area may not function as expected if heavy visitor use changes how animals behave within it.
The authors argue that conservation planning needs to take direct human presence more seriously. Rather than relying only on fixed boundaries or strict exclusion zones, some impacts might be reduced by managing when and where people use sensitive areas.
That could mean adjusting the timing of traffic, recreation or other human activity during important breeding, migration or feeding periods. For birds that rely on patchy habitats, or species that are sensitive to disturbance, such timing could make a real difference.
The study does not claim that every response is necessarily harmful. Some species may exploit human activity, while others may be pushed into poorer habitat or forced to move less. But it does show that animals are responding to people in ways that are more complicated than habitat maps alone can reveal.
For conservationists, the message is clear: the physical presence of people is not just background noise. It can be a direct ecological pressure, shaping where birds and mammals go, how much space they use and which habitats they are able to occupy.
May 2026
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