American kestrels are showing signs of stress and are abandoning their urban homes due to constant noise in these areas. For these small colorful falcons, living alongside humans has become increasingly difficult, reports a new study.
Urban areas with short grasses inhabited with insects along with telephone poles are a good place to live for these birds. However, researchers have found an increase in stress hormone levels in birds, especially females, living in these areas.
The study was conducted by Erin Strasser, graduate student from Boise State University, and Julie Heath from Boise State Department of Biological Sciences and Raptor Research Center. They monitored nest boxes located along the area's roadways and collected blood samples from some of the birds.
Researchers were specifically looking for a hormone called corticosterone in the blood sample. This hormone is known to cause behavioral and physiological changes in the birds. A similar kind of hormone called cortisol is present in the human blood.
The study showed that female kestrels living near noisy roadways have a higher corticosterone level. However, no such increase was seen in male kestrels. Researchers hypothesize that females might have more exposure to these noises because they spend more time in the nest boxes. When there is a lot of ambient noise, the birds can't detect any danger in the environment, which increases their stress levels and makes them anxious.
Researchers found that kestrels living near busy roads were 10 times more likely to abandon their nests than those living in remote areas.
"Birds evolved in an environment that was not dominated by humans. In recent history, human roads and structures have left few areas untouched. We're just starting to understand the real consequences," Heath said in a news release.
The study paper, "Reproductive failure of a human-tolerant species, the American kestrel, is associated with stress and human disturbance", can be found in the British Ecological Society's Journal of Applied Ecology.