How suburban sprawl might disrupt songbird mating

Over the course of a 10-year study, University of Washington researchers found that human development caused 'divorce' – and had a negative impact on reproduction – for some songbird species.

|
John Marzluff/University of Washington/File
The song sparrow is considered an 'adapter' or 'exploiter' species that tolerates or even thrives around human development. A new study from the University of Washington finds that suburban sprawl has a negative effect on the breeding populations of some songbirds.

The divide is familiar enough to any suburban adolescent: for some, the suburbs are made to be avoided; for others, the idea is to flock there.

Researchers from the University of Washington say as forests turn into subdivisions, certain species of human-shy songbirds – dubbed “avoiders” – are losing their mates as they flee for more propitious territory, causing some to miss as much as half of their breeding years, according to a study published in the journal PLOS ONE.

“These birds don’t like to move once they have established a territory,” lead author and UW wildlife scientist John Marzluff told the university’s news service. “But when it comes to having enough food and safety for a nest, and being able to attract a mate, that’s when things get tough. That’s probably when they decide to move.”

The study, which spent a decade observing six different species of songbirds that make their home outside Seattle, is one of the few to focus on how birds’ displacement by human habitation can influence their mating habits.

“Breeding dispersal – the annual shift in an adults’ center of reproductive activity – remains one of the least understood yet fundamental processes by which animal populations adapt to their environment,” the team wrote.

Urbanization didn’t augur decline for all of the songbirds: Two of the six species, the Pacific wren and the Swainson’s thrush, turned out to be avoiders; the other four types, which the researchers dubbed “adapters” or “exploiters,” stayed put as humans encroached on their old territory, without any apparent disruption of their reproduction.

That shouldn’t necessarily be taken as a sign that co-habitation with humans works out for most species. In the tropics and other places where species diversity is greater, Dr. Marzluff said, new developments could pose a greater risk to reproduction.

That seems to square with past studies that point to loss of habitat as a primary threat to birds’ numbers. One 2014 study from the National Audubon Society of 588 species found that 314 could lose more than half of their range, with 126 of them having no place to go, as The Christian Science Monitor reported at the time:

Conservation efforts have made important strides in stemming or reversing the decline of a variety of birds across the United States, but the regional effects of global warming could seriously erode those gains, researchers say....

Wetland birds are making a comeback in places where conservation efforts – under legislation such as the North American Wetlands Conservation Act, the Clean Water Act, and farm-bill conservation provisions – have been most intense, Dr. Rosenberg notes. The population of mallard ducks, for instance, is now 42 percent above its long-term average. Still, wetland losses continue to fuel declines in marsh species native to the US Southeast.

In America's grasslands, populations of many species have stabilized after years of losses, although Eastern meadowlarks and bobolinks continue to decline sharply as changing dairy practices and spreading suburbs have reduced available grasslands.

“To conserve some of these rarer species in an increasingly urban planet is going to require more knowledge of how birds disperse,” Marzluff said of the songbird study. “I expect that as we look more closely, we will find birds that are compromised because of us.”

You've read  of  free articles. Subscribe to continue.
Real news can be honest, hopeful, credible, constructive.
What is the Monitor difference? Tackling the tough headlines – with humanity. Listening to sources – with respect. Seeing the story that others are missing by reporting what so often gets overlooked: the values that connect us. That’s Monitor reporting – news that changes how you see the world.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to CSMonitor.com.

QR Code to How suburban sprawl might disrupt songbird mating
Read this article in
https://www.csmonitor.com/Environment/2017/0104/How-suburban-sprawl-might-disrupt-songbird-mating
QR Code to Subscription page
Start your subscription today
https://www.csmonitor.com/subscribe