A University of Colorado at Boulder study shows strong evidence that noise pollution negatively influences bird populations by reducing species diversity and increasing reproductive success of the birds in noisy areas.
The study published June 23rd in Current Biology, is the first to indicate that at least some bird species opt for noisy areas over quiet ones, perhaps because of their vocalization pitches, a reduction in predators and reduced competition from other songbirds that prefer quiet environments.
The three-year study compared bird nesting habits surrounding a Colorado natural gas supplier’s well with birds nesting in nearby, quieter woodland sites. The variety of bird species declined at noisy sites, and the bird nesting success rate was higher than in the nearby quiet sites.
Study shows that natural gas wells affect bird populations
The study reports that 32 different species nested in the quiet areas, while only 21 species were nesting in the noisy areas. Also, only three bird species nested exclusively at the noisy sites, while 14 different bird species nested only in the quiet sites.
One factor in preferring noisier environments is that some birds vocalize at a higher frequency than the “rumble” of the industrial compressors, which may allow them to communicate above the noise. Another factor is that noise deters the number of predators in the area, as the study showed that birds that nested in quiet areas were subject to higher rates of predation.
Ninety-two percent of the black-chinned hummingbird nests and 94 percent of house finch nests in the two study areas were found at sites near noisy compressors. The two species accounted for 31 percent of the nests at the noisy sites, but less than 3 percent on the quiet sites.
House finches and black-chinned hummingbirds produce vocalizations at higher acoustic frequencies than those generated by compressors, which may allow them to communicate above the “industrial rumble” and subsequently nest there.
Higher nesting success at noisy sites by house finches, black-chinned hummingbirds and of other species was due to lower levels of predation by the western scrub jay – which was shown to prefer the quiet woodland sites.
Western scrub jays, which are known to prey on eggs and young of songbirds, play a key role in Southwest woodland ecology. They were shown to be 32 percent more common in the quiet areas.
The team determined that 97 percent of mourning dove nests and 100 percent of black-headed grosbeak nests in the study area were found in the quiet areas away from the sound of compressors. The low vocal frequencies of mourning doves and black-headed grosbeaks appear to overlap with most human-caused noises, which may inhibit communication required for repelling rivals, pairing and nesting.
The study indicated birds that were intolerant of noise and nested in quiet areas were subject to greater rate of nest predation than those in noisy areas, he said. Woodland birds that prefer noisy areas may even use the clamor of civilization as cues for nesting, since such noise might signal a reduction in potential predators.
The researchers also found that a number of bird species found in the noisy sites – including gray flycatchers, gray vireos, black-throated gray warblers and spotted towhees – tended to avoid areas of noise disturbance when selecting nesting sites.
1 comment
Rob says:
July 28, 2009 at 12:00 am (UTC -5 )
Wow! I would never have thought any of this. I figure a noisy area is not fit for the birds other than typical city birds such as Pigeons, Sea gulls and European Starlings! I’m quite curious to know what 3 species exclusively nest at the noisy site.