By John Marzluff
When many of us think about nature, we imagine a pristine preserve far from the city center, not the partially paved places where most of us live and work. But John Marzluff, a University of Washington professor and ornithologist, has come to a surprising realization: Suburbs are bustling with bird diversity, sometimes even surpassing that of forests. In an excerpt from his new book, Welcome to Subirdia, Marzluff presents 10 ways you can help the birds in and around your own backyard, and connect with nature in your daily life.
My research and that of other urban ecologists suggests that, despite the great loss of biodiversity caused by our actions, we also have a lot to celebrate. I've spent most of my spring and summer mornings counting birds in national parks, industrial parks and suburbs. It is not surprising that the most-heavily paved portions of the city hold few birds, but it is not the case that the least-disturbed places on Earth always hold the most birds. Wild reserves provide shelter for unique birds not found in the city, and they are absolutely essential. But the greatest variety of birds is often found in the suburbs.
With my graduate students I have counted birds from Seattle’s urban core to its fringing forests nearly every spring and summer morning for the past decade. We expected the suburbs between the city center and the forested reserves to support an intermediate number of species, but when we listened as these neighborhoods awoke each morning, we were astonished by the dawn chorus of thrushes, tanagers, wrens, towhees, finches, crows and woodpeckers. Here we often tallied 30 or more species in a single count. We found birds from the industrial city mixed with some from the protected forest, and we encountered a whole new set of birds that use more open country.
Compiling standard bird surveys from more than 100 locations in and around Seattle revealed to us a consistent, but unexpected, relationship between the intensity of development and bird diversity. The greatest diversity was not in the most forested setting. Instead, bird diversity rose quickly from the city center to the suburbs and then dropped again in the extensive forest that eases Seattle into the high Cascades. We had discovered “subirdia.”
Human neighborhoods are good for birds because they offer a wide range of habitats in a small area. Lawns and trees are jumbled into savannahs, fields and woodlots. Engineers provide new features such as small ponds that retain runoff from the many sealed surfaces. Where different habitats touch, they produce rich edges that offer access to many resources, such as nuts from trees, seeds from annual weeds and insects from ponds. The diversity of plants found together in urban settings is simply incredible.
Our discovery of subirdia in Seattle is not unique. Throughout Britain, in deciduous woodlands of California and Ohio, grasslands of Arizona, forests of Japan, and shrublands of Australia, moderate levels of urbanization also provide an abundance of various resources that increases the number of bird species beyond that found in either wilder or more densely populated settings.
Subirdia is the place many of us call home or work. Physically, it is a richly interwoven mixture of residential, commercial and wilder land. Houses, allotments and gardens, derelict and vacant land, golf courses and other outdoor sports sites, cemeteries, schoolyards, highway and railway verges, municipal utility stations, business parks and shopping centers occur among places dominated by natural vegetation such as greenways, river and stream corridors, parks and nature reserves, pipelines and power lines, steep slopes and quarries. In a variety of locales, natural vegetation constitutes one-third to two-thirds of subirdia. Functionally, subirdia is the confluence between city and country that promotes a mutual exchange of plants and animals. It is also a place where people from urban and rural cultures come together as neighbors, friends and acquaintances. In so doing, we learn how varied is the human perception of nature.
As our modification of the land combines birds into new communities, we create interactions that have never before been seen and rekindle others that played out long ago. The interactive strands that link subirdia’s birds into an ecological web are as varied as the myriad animals that reside there. Some strands in the web are deadly, but others are supportive. As we now more fully consider a variety of ecological interactions, we learn about each bird’s place in the web of life and begin to see ourselves in that web as well.