Explore Portland’s neighborhoods and you’ll likely come across the occasional house displaying a “Certified Backyard Habitat” sign. Urban gardens with this certification and there are over 4,500 of them in the metro region, have met a series of strict standards established by the Audubon Society of Portland and the Columbia Land Trust and are recognized for efforts that promote a healthier city for people and wildlife.
If the City of Portland had a backyard, it would be our public parks and green spaces. And just as not every backyard provides the best habitat for wildlife, not every park is ideal for plants and animals native to the region. According to Michael Murphy, an ecologist and ornithologist, some of the best wildlife habitat in the city are in forested parks with abundant canopies and limited infrastructure. Murphy is a biology professor at Portland State University. His research focuses on the population biology of vertebrate animals generally and birds in particular.
For much of the past decade, Murphy and the graduate students he mentors have studied native birds like the spotted towhee and woodpeckers living in local parks including Forest Park, the Smith and Bybee Wetlands Natural Area, Thousand Acres Park, Mts. Tabor and Scott, and Kelly Point, among others. Murphy’s research seeks to answer several questions critical to the conservation of species within forested city parks and the preservation of regional biodiversity and urban forest health.
The species Murphy studies provide essential ecosystem services that support the web of life that makes our forested parks what they are. Ground-nesting towhees provide insect control and support populations further up the food chain, while woodpeckers are environmental engineers whose feeding and nesting habits result in other species gaining access to food and shelter.
“Our research is concerned with the population biology of birds living within and on the edges of city parks,” Murphy said. “So, how much space do they need to be successful? How many offspring are produced and how many adults survive? By answering these questions, we can get at the bigger question: are populations self-sustaining?”
Nowhere is the balance between populations of the city’s forest-dwelling birds and its human residents more tenuous than at the interface of urban development and forested parks. As Murphy noted, the edges of parks can be dangerous places for birds. Microclimatic changes, invasive species, domesticated predators, light and noise pollution all impact reproduction and survival rates for the birds and other animals that make their homes at the edges of these parks. But there are potential benefits to nesting in these areas as well, including increased access to food and water from bird feeders and baths during the warm, dry summer months and the potential to encounter mates. According to Murphy life on the edge can be dangerous, but some species, like the towhee, manage despite the risk.
“The metro region is projected to double its population in the coming decades, and if we want to preserve the species of birds living in our forested parks, we’ll need to know what they require to survive in our urban environments,” Murphy said. “The work we’re doing in our city parks can help inform planners tasked with making sure the city grows in such a way that doesn’t result in critical loss of habitat or biodiversity that could fundamentally change these unique ecosystems.”
A growing body of research indicates the benefits of forested parks range from improvement in human health for city dwellers to reduced urban heat island effects to air quality, stormwater collection, and much more. But like all ecosystems, urban forests are fragile and often intimately linked to the surrounding urban landscape. An understanding of the population biology of species living within these habitats can help us measure the health of our city parks and that knowledge, in turn, can be used to promote a healthier city for all humans and wildlife.