[Editor's note: Dr. Rich Kostecke is associate director of research and planning for The Nature Conservancy of Texas. Well-versed in birds and arthropods, his areas of expertise include migratory and wide-ranging species, biological monitoring, stewardship and restoration, and wildlife management.]
If you’re reading this, chances are good that you’re living and/or working in one of the world’s major urban areas. How do I know that? Well, in 2008 a little more than half of the world’s 7 billion people lived in cities. According to the United Nations, this marks the first time in history more people are living in urban centers than rural areas.
Such rapid growth could signal real changes for our environment—questions about smart development and the use of shared natural resources already abound—but our presence could mean even larger adjustments for species living in urban centers, such as the federally endangered golden-cheeked warbler. This Central Texas songbird makes its home within the city limits of Austin (14th most populous city in the U.S.) and San Antonio (7th most populous city in the U.S.).
According to some studies, urban noise from sources such as traffic and construction may cause birds to change their songs, forcing them to sing louder than they would typically to be heard so that they can successfully attract a mate or defend territory. Such changes to their songs could be taxing. If the bird is healthy, the increased energy required to sing louder may be no big deal, but what happens when other stressors, like drought or fire, compound the stress of all that urban noise?
To add a little salt in the proverbial wound, noise isn’t the only issue. The actual architecture of cities (i.e. skyscrapers, high-rise apartments and the like) can actually reflect and distort a bird’s song. Why does this matter? Since birds use song to establish and defend territories and attract mates, a trend of unheard bird calls could lead to any number of consequences, including a lower density of birds, lower nesting success (birds can’t reproduce if they miss a potential mate’s siren song) and wholesale changes to the entire avian community—in other words, species who cannot adapt their songs may ultimately disappear from cities even if suitable habitat exists.
So, in regard to the golden-cheeked warbler, Texas’ development boom could have them singing the blues. But there’s a silver lining—initial reports from Texas A&M University indicate that golden-cheeked warblers in central Texas have not shown any negative effects (so far) from the current levels of road noise—with one important caution. There does seem to be a noise level after which birds will experience negative consequences, it’s just a question of when that level will be breached.
But what does that mean in real terms? For years, The Nature Conservancy of Texas and various partners have strived to protect critical habitat for the golden-cheeked warbler within urban centers such as Austin and San Antonio. Efforts to protect sufficiently large and connected patches of habitat may have paid off in terms of allowing the warblers to be resilient to the stresses of the urban environment. However, it could be just a matter of time before birds at our urban preserves experience the impact of increased development and encroaching noise from the city.
It is definitely an interesting bit of science. The next time you’re stuck in traffic, roll down the window and take in the sounds: honking horns, trucks roaring past and nearby construction. While navigating rush hour traffic can be rough, imagine if your entire livelihood depended solely on the strength of your singing voice.
(Image: Golden-cheeked warbler. Source: USFWS via public domain at Wikimedia Commons.)