A recent review of North American bird life by the U.S. Interior Department and Audubon Society found steep declines in migratory bird species and forest-breeding birds over the past 40 years. Loss of habitat due to development is a leading reason.
But urbanization affects bird species unevenly, according to a long-term research project in the sprawling suburbs of Seattle, Washington. For the past 10 years, University of Washington Professor John Marzluff and his wildlife science students have surveyed birds on the city's urban fringes. They count birds, monitor nests, record behavior and catch and band birds to track survival rates.
Marzluff says he became interested in how urban sprawl affects bird populations after moving to a house out in the hills north of Seattle.
"Moving here, it was obvious what the major issue was for biodiversity in the western part of Washington. It wasn't forestry; it was urbanization," he explains. "So we immediately started to get some projects going."
Birds at home in the suburbs, too
As if on cue, developers broke ground on two major subdivisions less than a kilometer from Marzluff's house. His team monitored bird activity before and after. They also established 25 other research plots across the changing landscape of suburbia.
What he learned about where native songbirds thrive the best surprised him.
"The diversity peaks in these moderately settled subdivisions, what we think of as sprawl. We expected that sprawl would be the worst thing for birds, but, in fact, it increases diversity."
He points out that open areas, forest remnants and human-built structures offering ledges and crevices are all close together here. He says that variety of habitat in the typical leafy suburb promotes the feathered riches.
The finding jibes with what longtime neighborhood resident Milton Dick sees beyond his two hectare lot: more birds.
"All kinds," he says. "A lot of people feed 'em. A lot of people have bird feeders down here. The birds come back; year after year you see 'em."
He adds that new housing construction doesn't seem to bother the wildlife. "The deer and the coyotes, they go all down through here."
Putting out the welcome mat for feathered friends
The researchers are quick to add, there's good development and there's bad development. The choices people make can have a big impact on bird populations. Marzluff says property owners can help out by neglecting their yards a bit.
"People typically like fancier-looking shrubs, and they like things to be very neat. Birds like native shrubs and messy things. So be messy! Don't cut all the grass. Let some of it grow up and fall over so a junco can nest under it. The native ferns - and salmonberry especially - is an important species."
Marzluff also counsels tolerance for wild coyotes and bobcats. Their presence limits where house cats can safely roam, which is a good thing as far as native birds are concerned. Free-roaming cats kill millions of birds each year.
On the other hand, Marzluff has nothing but scorn for broad, perfectly trimmed lawns. He calls these subdivisions "Scrapervilles," because the land has been scraped clean of wild habitat. His decade-long tracking study found it makes a big difference when developers set aside even a little bit of forest, space the houses, maybe create a pond.
The National Science Foundation paid most of the bill for the first decade of this suburban bird tracking study. The science agency also funds parallel studies in the U.S. states of Arizona, Ohio and Maryland. Researcher John Marzluff, now 50 years old, hopes to keep the project going for the rest of his professional career, which could be another 20 years.