It's no secret that loud human sounds—the roar of traffic and hum of heavy machinery—is bad for birds, since fewer are found near such noisy areas. But some species, particularly larger birds that sing low-pitched songs, such as western tanagers, especially suffer from man-made cacophony, scientists report in today's PLoS One. Researchers counted birds and nests in the Rattlesnake Canyon Wildlife Area of northern New Mexico, which is close to thousands of natural gas wells, many of which are coupled with constantly roaring compressors—think of listening to a motorcycle that's about 15 meters away. After surveying some 30 species of birds, ranging from black-chinned hummingbirds to mourning doves, the researchers discovered that it was the larger birds, like the mourning doves and western tanagers that kept away from the noise. Such large birds may be forced out of the loud areas because the roaring machinery drowns out their lower-pitched songs, making it difficult for them to hear each other, the scientists say. Smaller birds, such as chipping sparrows, sing in a higher-pitch, and these species weren't as affected, presumably because their melodies can still rise above the din.
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