

By Ed Yong | July 27, 2009 8:30 am






The team found that fewer species of birds lived near the louder gas wells. Some species like the mourning dove and the black-headed grosbeak were almost exclusively found near the silent sites. It’s no coincidence that these birds have very low-pitched calls, with frequencies that overlap with most man-made noise. Theirs are the tunes most likely to be masked by the compressors. And other species nested further away from the wells at the loud locations than at the quieter ones, including flycatchers, vireos and warblers.

As expected, noise was off-putting to several species of birds and it has a negative impact on the richness of local species. But it didn’t seem to impact the total number of feathered residents. Francis found the same number of nests near the two types of wells, so clearly, some species were thriving in the noisy neighbourhoods and compensating for those that were driven away.

Noisy woodlands weren’t bereft of birds, but they were represented by different species. In particular, black-chinned hummingbirds and house finches positively preferred real estate near noisier places and the vast majority of both species were found near sites with compressors. The hummingbirds’ calls have some low-pitched components but they mostly stay within high registers that rise above man-made dins. Likewise, we know that house finches are capable to raising the pitch of their songs in response to urban noise. That certainly explains why they can survive in noisy areas, but not why they seem to actively prefer such spots.

The draw of the noisier venues was a lack of predators. For smaller birds, egg-eating predators, like the western scrub jay, are the major cause of nest failure. But noise affects the jays too, for they are another species with easily masked, low-frequency calls. Their intolerance means that they are less common at noisy sites than at quieter ones.

This means that at loud sites have both drawbacks and benefits – it’s harder to be heard, but the broods of small birds are less likely to suffer at the beaks of egg thieves. For birds that managed to tolerate the din, their chicks were more likely to hatch. Even species like the gray flycatcher that prefer to nest away from the noise, nests were more likely to escape the attentions of predators at louder locations.

Francis’s study illustrates the complex effects that a single factor – in this case, man-made noise – can have on an ecosystem. The scrub jay may take the eggs of small birds but it is also important for the pinyon pine trees that make up the bulk of the woodlands. By dispersing seeds, it contributes to the overall health of the forest so if it’s being driven away by noise, small birds might benefit in the short-term but the entire community might be harmed in the long-term. Understanding these effects will become ever more crucial as the spread of human activity makes the natural world a noisier one.

Images Finch by Matthew Field, hummingbird by MDF; gas wells by Clinton Francis

More on conservation:

Reference: Francis, C., Ortega, C., & Cruz, A. (2009). Noise Pollution Changes Avian Communities and Species Interactions Current Biology DOI: 10.1016/j.cub.2009.06.052

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CATEGORIZED UNDER: Animals, Birds, Conservation, Ecology
MORE ABOUT: bird, noise pollution, urban

Comments (2)

  1. Unfortunately, noise pollution doesn’t scare black squirrels, which are a major predator of eggs and nestlings.

  2. I have noticed birds using truncated, simpler calls in my urban neighbourhood. They seem to fit better into the pauses between traffic noise.
    I recently put up a bird feeder and am getting birds that I never saw before. The other big draw is a cherry tree, which gets rare but welcome visitors such as orioles, tanagers, and warblers.


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