Even in the concrete jungle that constitutes much of Manhattan, I often hear the delightful strains of birdsong. It may be only background music, but oh, what a difference it makes! Better than an iPod for elevating my mood.

Songfests occur not just in Central Park, but in unlikely places, too. Inside my apartment, I regularly hear birds calling from the courtyard out back, though the only greenery it offers is a few potted shrubs. I have noticed birds cheeping in the eaves of buildings on treeless streets and was once serenaded by a bevy of birds in a small grove by the Holland Tunnel.

With birds so omnipresent here, in this inhospitable urban environment, I never thought their overall survival was anything to worry about. Yet a new report from Audubon says otherwise. Over the past 40 years, the populations of 20 species of common birds have plummeted. While I was daydreaming, the songs in the air had grown fewer and farther between.

The northern bobwhite tops Audubon's list of common birds in decline. Though it has a high reproductive rate, is not a picky eater and has a fairly large range, its population has dropped 82 percent over the past four decades, from 31 million to 5.5 million. The problem is that its habitat -- grasslands with shrubs and widely spaced trees -- has been giving way to large-scale agriculture and development.

At the other end of the list are the little blue heron and ruffed grouse, both of whose populations have declined a "mere" 54 percent. The herons, which now number 150,000, live in the south where poor water quality is affecting their food supply. Meanwhile, the grouse, with 6.8 million members, is losing habitat up north to logging and overgrazing by deer. Threats to other species include mining, drilling, forest management practices and global warming.

While none of these species is in danger of disappearing anytime soon, the sharp downward trend in their numbers alarms scientists, as does the fact that it cuts across so many species and results from such diverse causes.

There is no magic bullet to counter the trend, but there is much that you can do personally to help.

One is to create your own patch of habitat around your home by sowing some (or all) of your yard with native grasses, shrubs and trees. This will have the effect of forming a small oasis in the desert of lawns -- a place where birds can find food, shelter and nesting sites. If there is no source of water on your property, you might add a bird bath, too. The obvious side benefit to you is the amount of wildlife you'll see -- not just birds, but butterflies and possibly small mammals, too.

Another way to help is to buy recycled paper products -- including tissues, toilet paper and (if you must use them) paper towels. Why? Because paper products not made from recycled materials are made by cutting down trees, aka bird (and other wildlife) habitat. Much of that cutting goes on in the Canadian boreal forest, a breeding ground for up to 3 billion birds each spring.

Third, save energy to help put the brakes on global warming, which wreaks havoc with bird habitat. You probably already know several ways, but here are a few to get you started: replace your incandescent bulbs with compact fluorescents, unplug your chargers and equipment when not in use and buy energy-efficient appliances bearing the government's Energy Star label. When it comes time to buy a car, look for a model with high mileage per gallon. It need not be a hybrid, just a fuel-efficient car.

These steps may seem like an awful lot of trouble for species that still number mostly in the millions. But if action isn't taken to shore up their habitat now, it won't be long until their populations dip into the thousands. Just do the math. A population of 5.5 million, as the northern bobwhite has today, that declines by 82 percent every 40 years, would be less than 180,000 by the end of this century -- and virtually extinct by the end of the next.

Humans might need to make all their own music then.

—Sheryl Eisenberg

ONLINE RESOURCES AUDUBON Common Birds in Decline AUDUBON Every Backyard Is Important NATIONAL WILDLIFE FEDERATION Garden for Wildlife PROJECT FEEDERWATCH Birds and Bird Feeding SAVE BIOGEMS Saving Our Greatest Bird Nursery NRDC How to Save Energy MACAULAY LIBRARY Animal Sounds & Video Archive

What are "common birds"? Audubon defines them as "species with more than 500,000 individuals worldwide, with a range of more than 385,000 square miles."

The boreal chickadee is one of the common birds in decline, having lost 73 percent of its population in the last 40 years.

Black tupelo is on the National Wildlife Federation's top ten native plant list for the northeast. Both birds and mammals enjoy its fruit.

Easy, cheap and good. Since native plants are adapted to local conditions, they are easier and cheaper to maintain than conventional grass and plantings. Once they are established, they generally grow on their own -- without fertilizers, pesticides or watering. This is beneficial not just for birds, but for the environment at large.

Buy recycled tissue products listed on NRDC's wallet-sized shopping guide to help save bird habitat.