Greening the Urban Desert

Even small green spaces may add up to help wildlife

By Viviana Ruiz Gutierrez and Timothy Vargo

Imagine yourself on a long-distance road trip from New England to Florida. Cars have great amenities—music, plush seats, beverage holders, maybe even a Global Positioning System to prevent you from getting lost. But no matter how comfortable you are, you will eventually need to pull over and look for a place to eat and get a good night's sleep.

Migratory birds face similar constraints. They can fly more than 1,000 miles at a time but eventually they too need to find stopover places to rest and refuel. With the steady increase in urbanization, more and more birds will need to find stopover habitats in urban environments. This underscores how important it is for humans to provide green spaces with adequate food and shelter.

In Milwaukee, green forested corridors along the Milwaukee River and Lake Michigan provide habitat for migrating birds and other wildlife in a sea of development. Suitable habitat can be extended through careful urban planning and native wildlife landscaping by neighborhood residents.

Some large cities, such as Milwaukee and Minneapolis, have forested riparian corridors that go right up to downtown areas, allowing animals such as Yellow-crowned Night-Herons or American beavers to take shelter within blocks of the concrete jungle. New York and Boston have large parks that act as island oases amid a sea of development. However, other cities have hundreds of square miles of development without green space, acting effectively like a desert.

Do birds only benefit from larger parks, or are small habitat patches, and even home gardens, helpful too? To determine if a "threshold" amount of habitat is needed to attract native birds to urban areas, Will Turner, a scientist at Conservation International, looked at the responses of desert scrub bird species to varying amounts of habitat in Tucson, Arizona.

Gambel's Quail and other birds could live in urban areas if suitable habitat increases by 6-15 percent, one study found.

Elroy Limmer

He found that for species such as Gambel's Quail to occur in an urban setting, the total amount of desert scrub habitat needs to increase from around 6 percent to 15 percent at both a local and landscape level. He suggested that this goal could be achieved by restoring areas such as private landscaped yards and open spaces, as well as larger parks.

This Connecticut Warbler was found less than a mile from downtown Milwaukee.

Photo by Tim Vargo.

In addition to size, researchers are trying to determine characteristics of green space that most benefit migrating birds. We often use the birds' presence or absence to determine the effectiveness of a habitat, but this doesn't necessarily reflect the habitat's quality. A bird may land in an urban tree simply because it has no other option.

Bill Mueller of the Milwaukee County Avian Migration and Monitoring Partnership, and Chris Guglielmo of the University of Western Ontario are spearheading research to use bird physiology as an indicator of habitat quality. Circulating lipid metabolites in birds reflect their body condition and refueling rate, and a blood sample reveals how well or poorly a bird is faring in a given habitat. Research like this will help determine how migrating birds are affected by native landscaping in your backyard or the removal of exotic plants from green spaces.

In urban areas such as Tucson, Arizona, more habitat for birds can be created by restoring private yards and open spaces, as well as large parks.

Brian McMorrow

Green spaces in cities benefit more than just our migratory birds and other wildlife. Vegetation lowers temperature from the "heat island" produced by concrete, decreases erosion, tempers runoff during rainstorms that overload sewage treatment plants, and helps control flooding. And, as was shown with the birds in Tucson, every little bit of habitat makes a difference toward reaching the "threshold" amount for many species of conservation concern.

There are many ways you can help achieve suitable habitat levels where you live, from placing a single plant on your balcony to restoring your garden or yard with native plants that attract birds and other wildlife. You can also help restore, create, or maintain green spaces in your city. We hope you'll join efforts to help out in your own way during the "Celebrate Urban Birds!" event this spring (see page 10).

Viviana Ruiz Gutierrez is a Ph.D. candidate at the Cornell Lab of Ornithology. Timothy Vargo is research coordinator at the Urban Ecology Center in Milwaukee, Wisconsin.

For permission to reprint all or part of this article, please contact Laura Erickson, editor, Cornell Lab of Ornithology, 159 Sapsucker Woods Rd., Ithaca, NY, 14850. Phone: (607) 254-1114. email: lle24@cornell.edu