Creating a Bird-Friendly Yard
New research shows that small habitats can add up to a big difference.
One of Tallamy's studies examined the moth and butterfly larvae that develop on indigenous and exotic plants in the mid-Atlantic region (Virginia, Maryland, Delaware, Pennsylvania, New York, New Jersey, Connecticut, and Rhode Island), where you can find roughly 3,000 of the country's total of 11,500 caterpillar species. From his findings he created a ranking system of regional trees and plants by the abundance and diversity of caterpillars they can host. First place on the top 20 list went to the oaks, which supported 534 species of caterpillars. Second place went to cherries and plums, which were home to 456; willows came in third, with 455.
The study confirmed Tallamy's suspicions that gardeners could play a pivotal role in creating safe havens for wildlife. (An estimated 85 percent of invasive woody plants spreading through wild areas originally escaped from home gardens.) Thus he opens his landmark book, Bringing Nature Home,with a call to action: "For the first time in its history, gardening has taken on a role that transcends the needs of the gardener. Like it or not, gardeners have become important players in the management of our nation's wildlife. It is now within the power of individual gardeners to do something that we all dream of doing: to make a difference. In this case, the 'difference' will be to the future of biodiversity, to the native plants and animals of North America and the ecosystems that sustain them."
Many gardeners and botanists regard Tallamy's book as the seminal source, and sales remain strong--the paperback is in its seventh printing. Throughout it, Tallamy avoids the term backyard habitat, because he says "it implies that these are so terrible we have to hide them in the backyard. When in fact the front yard is fair game. We're not talking about creating ugly landscapes. A beautiful oak tree in your front yard is a highly functional plant there."
Homeowners who landscape with native trees and plants such as oaks, goldenrods, asters, cherry trees, and sunflowers are planting bird food factories that ship caterpillars in bulk, and make regular deliveries of fruits and seeds that help fuel bird migrations over thousands of miles and multiple continents. "The plants in our yards are just as effective as the bird feeder you put up in wintertime," Tallamy says, "because the plants are making the food that feeds the birds in the summertime."
For a bird searching for a nice place to raise a family, the classic suburban yard--a tidy bed of grass, one or two shade trees, and a row of leafy foundation plantings imported from China--must be like a foreclosed fixer-upper in a bad neighborhood. The accommodations are spare and all the local restaurants are dives.
The nice neighborhoods, on the other hand, where native plants abound, offer all the perks of a Park Avenue suite with a stocked pantry and a view. There is abundant food, places to nest, and a brilliant stage upon which a bird can sing without competing against the din of a lawn mower.
One of Tallamy's undergraduate students, Karin Burghardt, compared two such types of landscapes in southeastern Pennsylvania. One property in each of six pairs had a higher proportion of native plants, and the other was more typically suburban, with an indigenous tree canopy casting shadows on lawns fringed by alien ornamental bushes and ground covers like pachysandra.
Not surprisingly Burghardt found a greater diversity and abundance of birds and caterpillars in the yards filled with naturally occurring plants. But one finding blew the researchers away. Birds of conservation concern in the area where the study was done--wood thrushes, eastern towhees, veeries, and scarlet tanagers--were eight times more abundant and significantly more diverse on those parcels. "There was a big jump in their ability to use these properties," says Tallamy.
During the three months it took Burghardt to gather data, 125 square miles of lawn grew across the country, even in areas where you wouldn't expect to find grass growing. In Phoenix, Arizona, where temperatures can hit 120 degrees Fahrenheit, the popular garden "oasis" is a mix of turf, subtropical palm trees, and a scattering of desert-adapted plants. Susannah Lerman, a researcher from the University of Massachusetts-Amherst, traveled there to examine the difference between how birds use the "oasis" compared to grounds brimming with native desert plants (a gardening style known as xeriscaping; see "Hollywood Native.").
The well-watered oasis yards were ruled by grackles, house sparrows, and European starlings--everyday birds that wouldn't normally survive in such a hot and dry place. "You're not going to see those species naturally in the desert because they can't make it without water," she says. "But as soon as you add water--boom."