Did you realize it is not only enviromental contaminants that effects birds? A study at the University of Colorado at Boulder shows strong evidence that noise pollution affects birds, too. Although there is no clear definition of noise pollution, noise pollution are waves that interfere with naturally occuring waves in the environment. The biggest source of noise pollution comes from transportation.
The study compared birds nesting near a natural gas extraction site with noisy compressors to birds nesting in the quieter, adjacent woodland sites. They found that the diversity of bird species declined near the natural gas extraction sites while the bird nesting success was higher at the woodland site. The researchers found that only 21 species of birds were nesting near the gas extraction site while 32 different species nested in the nearby woodland area. However, two birds species seemed to prefer the gas extraction sites. The majority of the nests of black-chinned hummingbirds and house finches were found at the natural gas extraction sites. One theory for this is that their ability to produce vocalizations at a higher frequency than those generated by the compressors may enable them to live there. Additionally, their higher nesting success may be due to less egg predation by the western scrub jay. Western scrub jays apparently prefer the quiet, woodland areas.
In an European study, researchers studied urban-dwelling great tits compared to forest-dwelling great tits. They found that urban dwelling great tit's songs were shorter, faster, and a higher frequency than the great tits living in the forested areas. Bird songs are not only important for mate attraction, but they are used to defend their territories, too.
In addition to these studies, other studies have found that city noise drives away birds with low-pitched songs. Seemingly, as forested areas dwindle and noisy, sprawling urban areas take over the country-side, a bird's ability to survive is becoming increasingly dependent upon their ability to adapt their vocal calls. Unfortunately, those that can't adapt may one day become extinct.
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