Even in the Big City, a Shaggy Back Yard Can Be a Lifesaver for Wildlife : Environment: Home landscapes, school grounds and pocket parks, one biologist says, can provide considerable living space for birds, small mammals, insects and some amphibians.

If the black swallowtail was somehow off track in a cluttered downtown alley, it wasn’t evident.

The ghostly butterfly glided purposefully on tattered wings between rows of townhouses, the same buildings that had crushed her ancestors’ habitat more than a century ago.

Alighting finally on a potted parsley in someone’s back-porch herb garden, she deposited the last of her eggs. Then she flew off to die.

Wildlife biologists have many theories about why butterflies, beavers, deer, mountain lions and other wild animals have begun moving into human territory after centuries of separateness. Many see the phenomenon as the answer to a prayer.

Appropriately landscaped human habitat, they say, can help tackle the problem of dwindling biological diversity.

“It’s true, not many people are going to save a species in their back yard,” said Craig Tufts, who heads the National Wildlife Federation’s back yard habitat program. “But we can significantly increase habitat for some of the smaller critters.”

The aggregate of thousands of back yards, school lots and pocket parks, he says, can provide considerable living space for birds, small mammals, insects and some amphibians.

The federation’s program was launched almost 20 years ago as a way to involve members who primarily were interested in feeding birds. A garden of berries, fruits and places for nests was a way to attract many more species than just seed-eaters.

Over the years, the notion of the wildlife garden has expanded to include a complete habitat--food, water, cover and a place to raise young--for a full range of interrelated species of animals and plants.

“We’ve got to look at this incredible increase in extinctions by looking at everything we’ve got out there,” said Tufts. “Where there isn’t milkweed, there aren’t monarchs completing their life cycles. It’s just that simple.”

Today, the complete wildlife gardener landscapes with native plants, shuns chemicals, welcomes “weeds” if they are useful to wildlife and tolerates a shaggy-looking yard.

“It’s not always pretty, but it’s a lot less work,” said Nancy Davis, who allowed her sprawling lawn in Reston, Va., to go wild 15 years ago. “Once you stop mowing, boom, here comes the flora--and the fauna. It’s wonderful.”

Herb gardens double as nurseries for butterfly caterpillars. Hedgerows provide homes for rabbits and pheasants. A small plot of corn makes a rest stop for migrating geese.

The newest twist is the water garden, a sort of wetland in a tub. Kits that include plastic liners and water pumps are sold at some garden centers and hardware stores.

“Typically, people start out with an aquatic version of the lawn--one or two waterlilies, a fountain and some carp that cost $50 apiece,” said Tufts.

“Frogs will show up in the darndest places,” he said. One such place is downtown Raleigh, N.C. The city now has a stable population of tree frogs, thanks to volunteers who fashioned small wetland ponds from cattle-feeding troughs three years ago.

People who welcome wildlife to their property can be put to the test. Ravenous deer have been known to wipe out years of gardening in one night. Coyotes attracted by bird feeders have picked off small pets instead.

The problem of large predators roaming new suburban developments has become a contentious issue in the West, where sprawl sometimes meets country inhabited by bears and mountain lions.

“Our Rocky Mountains Front Range offers great habitat for mountain lions--and for condos,” said Todd Marlsbury, a spokesman for the Colorado Division of Wildlife. “We take the view that if you want wildlife, you have to learn to live with wildlife.”

The division’s educational brochures recommend that people who live in predator country make noise when they come home in darkness, accompany small children outdoors, bring pets indoors for the night, store garbage securely and fight back if attacked.

Agency officials often testify at public hearings on proposed housing developments and other construction projects that would alter natural habitat. “Our position is, factor in the needs of wildlife before you start building,” said Marlsbury.

In downtown Washington, the needs were simple: a new flower garden and a pot of parsley. The black swallowtail’s eggs hatched into caterpillars and relentlessly devoured the parsley.

Through the coming winter, the chrysalides, in bright-green casings, will decorate a low-slung branch. Next spring, adult butterflies will emerge, velvety black with spangles of yellow, blue and red.

As long as someone remembers to plant flowers and put out a pot of parsley that hasn’t been grown with chemicals, they will stay.