By: Susan Bird
Here’s something to think about whenever you pass by a new housing development. Researchers now say that as we continue to add to burgeoning suburban sprawl, we’re cheating songbirds out of the prime years of their reproductive lives.
University of Washington (UW) researchers released a study in December 2016 that paints a sad picture for certain types of songbirds. It seems that as we keep building houses and other infrastructure, we often disrupt their lives in ways they have a tough time recovering from.
The research team spent a decade following the movements and breeding habits of six types of birds who live in areas east of Seattle. Between 2000 and 2010, some of these sites transitioned from forested areas to new suburban developments. What happened to the hundreds of birds tracked in this study is a cautionary tale for us all.
Songbirds tend to fall into two types:
Avoiders – These birds mate monogamously, avoid places where humans are, and need groundcover and brush like felled trees, shrubs, ferns and root balls in order to breed. The Pacific wren and Swaison’s thrush are two examples of “avoider” songbirds in the Pacific Northwest.
Adapters/Exploiters – These birds do well around humans, aren’t always monogamous, and often live in backyards or birdhouses. They seem not to be bothered at all by the loss of forested areas or increased human activity. Bewick’s wren, the song sparrow, the dark-eyed junco and the spotted towhee are examples of “avoiders” or “exploiters”living in the Seattle area.
As you might expect, the “adapters” and “exploiters” studied by the team did pretty well when formerly forested areas underwent development. These birds are flexible and adaptable. They’re prepared to live, mate and begin a family nearly anywhere.
Photo credit: Thinkstock
Photo credit: Thinkstock
The “avoiders” didn’t fare as well. The loss of underbrush and trees proved devastating enough that they left the newly developed area entirely. For them, leaving means relocating to areas about the size of one and a half football fields away.
For a monogamous bird, having to flee home often ends up splitting mated pairs permanently. That meant the birds had to spend time finding a new home and then finding a new mate.
The life span of a bird isn’t particularly long. Unfortunately, UW’s researchers found that “avoider” birds lost up to half of their breeding years when forced to relocate. That’s not good. For rarer species, it’s especially problematic.
“The hidden cost of suburban development for these birds is that we force them to do things that natural selection wouldn’t have them do otherwise,” the study’s lead author, UW professor John Marzluff, said in a UW news release.
Most of us don’t even consider an impact of this type when we buy a parcel of property and build houses or a shopping center on it. We don’t think about the animals and birds who make a home in the trees and underbrush on that property. Maybe we assume they’ll head for the hills and find a new place to live.
Most probably do, but we’re often blissfully unaware of the long-term damage we might be doing to creatures like “avoider” birds. Without question, there are fewer of them around because our desire for more and more development affects their lives in profound ways.
“To conserve some of these rarer species in an increasingly urban planet is going to require more knowledge of how birds disperse,” Marzluff said in the UW news release. “I expect that as we look more closely, we will find birds that are compromised because of us.”
Losing your lifelong mate and half your breeding years is no small matter. As we continue to sanction urban sprawl, we risk compromising more and more bird species.
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