It always happens. When a person walks down the street and approaches the place where a bird perches, it ends up taking flight and fleeing. However, in some places the birds are more confident and take longer to escape than in others. A study led by researchers from the CSIC has analyzed the distances at which animals take flight , and concludes that in cities and in the northernmost regions of Europe, birds are more trusting.
The work, which is published in the journal PLOS ONE , is based on some 12,000 observations of 159 species of birds in nine areas of Europe. According to the data, the birds flee when the threat is at an average distance of 11.46 meters , although the measure varies depending on the species and the locality, since cases have been detected in which the potential predator can approach up to one meter and others in the limit is 180 meters away. The results showed that, once the effect of factors such as species, habitat or body size is separated, there is a relationship between latitude and distance. Also, birds are more trusting in cities than in rural areas.
“This work shows for the first time that there is a wide latitudinal gradient, at least in Europe, in the risk of predation suffered by birds,” explains Mario Díaz, from the National Museum of Natural Sciences (Madrid) and one of the authors of the study . The researchers believe that these differences are due to the number of predators, which is higher in southern Europe and in rural areas. “This phenomenon manifests itself in their behavior and is related to the abundance or scarcity of predators, such as raptors,” Díaz clarified.
