Bird Communities Affected by Noise Pollution

Researchers in Colorado have found that noise pollution adversely affects communities of woodland birds. The three-year study was led by Clinton Francis, a doctoral student in the Department of Ecology and Evolutionary Biology at the University of Colorado-Boulder. Two other scientists that contributed to the study were Dr. Alex Cruz, also of CU-Boulder and Dr. Catherine Ortega, a a former doctoral student of Cruz, of Fort Lewis College.

In their study, the scientists compared the nest number and nesting success of birds on noisy and quiet sites within a pinyon-juniper woodland surrounding natural gas extraction sites containing loud compressors in an area just over the New Mexico border south of Durango, Colorado. The scientists found that 32 species of birds resided in the quiet areas while only 21 species of birds inhabited the noisy areas. The researchers also found that two species of birds preferentially built their nests in the noisy areas—92 percent of all black-chinned hummingbird nests and 94 percent of all house finch nests were found in noisy spots. Two species that overwhelmingly preferred to nest in the quiet areas were mourning doves (97 percent of nests) and black-headed grosbeaks (100 percent of nests). The scientists think that this preference is due in part to the pitch of vocalizations each bird species makes; both black-chinned hummingbirds and house finches vocalize at a pitch higher than the compressor’s noise, meaning the birds can hear each other over the din of the machinery. In comparison, both mourning doves and black-headed grosbeaks vocalize at a lower pitch, which cannot be heard over the sound of the compressor.

The scientists’ research also indicated that those birds that built their nests in the noisier areas tended to have greater reproductive success and were less likely to suffer from nest predation than birds that nested in quieter areas. The researchers concluded that though noise pollution is preferable to some woodland bird species, most others are negatively impacted.

The results of the scientists’ study were published online in the July 23rd edition of the journal Current Biology. The study was funded through a variety of different sources including the Bureau of Land Management and the University of Colorado-Boulder.

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