Baldly back: guess what? Our national bird is flourishing.

IN February, a group of birdwatchers spotted something that no living person had ever seen before: a bald-eagle nest within the city limits of Philadelphia. "It's the first one that we know about for sure since the Revolutionary War," says Doug Gross, a biologist at the Pennsylvania Game Commission. A few weeks later the nest contained eggs. By now the two birds that built it are almost certainly the proud parents of one to three eaglets. Gross won't say precisely where the nest is located, but he reveals with a kind of hometown pride that it's along the Delaware River--"a couple of flaps and a glide away from the stadium where the Philadelphia Eagles play football."

Stories such as this are becoming downright common, even if they all aren't so poetic. On April 2, the U.S. Fish & Wildlife Service announced that two bald-eagle chicks had hatched unaided by humans on Catalina Island, off the coast of California, for the first time in recent memory. Around the country, aerial surveys are counting more bald eagles than ever before. Official totals for 2007 aren't available yet, but the Fish & Wildlife Service anticipates a population of more than 9,000 nesting pairs in the lower 48 states. At least one pair lives in every state except Hawaii, where the bird is not native. "In Virginia, we've produced more chicks in the past five years than in the previous 25," says Bryan D. Watts of the Center for Conservation Biology, based in Williamsburg. "Bald eagles have tremendous momentum right now."

This surge all but guarantees that the bald eagle will fly off the endangered-species list, where it has roosted for decades, within a few months. Bald eagles are by no means the only animals making impressive recoveries. In March, the Fish & Wildlife Service removed the Yellowstone grizzly bear from the endangered list. Gray wolves in the Great Lakes region came off in January and packs in the Rockies may join them soon.

Yet no other animal carries the patriotic punch of the bald eagle, which has served as the poster species of endangerment since the 1960s. At a time when gloomy greens would prefer to complain about planetary fever and the plight of the polar bear, the eagle's amazing comeback demonstrates that environmental success stories are not only possible but actually happening. "It shows that we can make a difference," says Lynn Scarlett, deputy secretary of the Department of the Interior. "These are not lost causes."

In truth, reports of the bald eagle's near-extinction have been greatly exaggerated. The vast majority of the species lives in Alaska and Canada, where it has always flourished. Today, the Fish & Wildlife Service doesn't know how many bald eagles reside in Alaska because there are too many to count: More than 50,000 is a conservative estimate. The bird's listing as "endangered" or "threatened" has never applied outside the continental United States.

For most Americans during the 20th century, however, a bald eagle was a rare sight. Because of the bird's symbolic importance, its troubles became a pressing political issue. In 1940, Congress passed a law making it illegal to kill or abuse bald eagles. Ever since, shooting an eagle has been permissible only in golf. That restriction may have helped, but it hardly turned things around. By 1963, when the first reliable survey was conducted, birdwatchers counted only 417 nesting pairs in the lower 48 states. If the species wasn't as doomed as the dodo, it was on the brink of what biologists call extirpation--a localized extinction.

The culprit was the pesticide DDT. Although incredibly effective at wiping out mosquitoes, it had devastating aftereffects as it worked its way up the food chain from bug to fish to bird. Bald eagles weren't the only species harmed. Peregrine falcons and brown pelicans also suffered population crashes. The ingestion of DDT caused their egg shells to thin and weaken. Eggs cracked open before their time, leading to massive reproductive failure. The DDT ban in 1972 was the tipping point in the bald eagle's recovery (as well as the recoveries of peregrine falcons and brown pelicans). The 1940 law and a 1991 ban on lead shot in waterfowl hunting also helped, but the elimination of DDT is the sine qua non of the bald eagle's ongoing population boom.

Environmentalists deserve a pat on the back for this accomplishment. Yet it also places them in a conundrum, because their achievement rests almost entirely upon a singular act that took place 35 years ago. They've compensated by trying to give equal credit to the Endangered Species Act, passed in 1973, and its relentless expansion ever since to cover the likes of the snail darter and to impose aggressive land-use regulations. Nowadays, environmental activists often wildly overstate the importance of that law, as Brian Seasholes, an adjunct fellow of the National Center for Policy Analysis, documents in an unpublished monograph. Defenders of Wildlife president Rodger Schlickeisen, for instance, has argued that "but for the Endangered Species Act, [the bald eagle] would have been extinct." That's just plain wrong: Remember all of those birds in Alaska, essentially untouched by DDT. Yet this sloppy claim is made over and over again. It's on the website of the Sierra Club right now.

The Endangered Species Act may not have helped much in the lower 48 states, either. Under the 1940 law, the bald eagle already enjoyed many of the protections it supposedly gained from the ESA. Moreover, the ESA's habitat-protection rules possibly had a detrimental effect. "The problem with the ESA is that it punishes people for having an endangered species on their private land," says Randy Simmons of Utah State University. "They lose their property rights." This can lead to a phenomenon known as "preemptive habitat destruction." Using data on the red-cockaded woodpecker, an endangered species in North Carolina, economists Dean Lueck and Jeffrey A. Michael showed that private landowners gained a powerful incentive to destroy potential habitat before the woodpeckers could occupy it. "They were more likely to cut down trees that the woodpeckers might find inviting," says Lueck.

Although no similar studies have been done on bald eagles--mainly because they're a national species with a large range, and therefore difficult to research in such precise ways--this type of conflict may become common. More eagles means more nests on private land as well as more landowners who will question whether a species that has recovered so well deserves extraordinary habitat protections.

In 1999, the Clinton administration called for removing the bald eagle from the endangered-species list--a proposal that led to years of bureaucratic dawdling. The delays might have dragged on indefinitely but for the actions of Edmund Contoski, who hoped to fund his retirement by selling about seven acres of lakefront property in Minnesota. "I'm not married and don't have kids," says Contoski. "There's no one to take care of me in my old age. I need the money." As he prepared his property for sale and development, a nearby resident called attention to an eagle's nest in a tall pine tree. That brought everything to a screeching halt: Contoski's land was suddenly rendered unbuildable. "The bald eagle wasn't endangered anymore, but our laws still treated it that way," says Contoski. He contacted the Pacific Legal Foundation, which helped him file a lawsuit. Last August, a judge ordered the federal government to remove the bald eagle from the endangered-species list.

The deadline is June 29. When it passes, bald eagles won't receive any protections under the ESA--but that 1940 law will still apply. The Bald and Golden Eagle Protection Act makes it illegal not only to kill or harm eagles, but also to "disturb" them. The Department of the Interior is currently trying to define this term. Some liberal groups would prefer an incredibly broad meaning. "The simplest approach would be based upon whether an eagle reacts to an activity in a way that's typical of agitation, such as taking flight and issuing its high-pitched call," says Michael Bean of Environmental Defense. The actual rule almost certainly will be narrower than this suggestion, which could conceivably forbid trucks to drive too close to nesting sites. Most likely, "disturb" will mean an activity that interferes with breeding. Whatever the result, Bush-hating environmental groups almost certainly have drafted press releases that savage the administration for sending bald eagles to their doom.

The good news is that although greater numbers means greater contact with people, the species as a whole appears increasingly difficult to disturb. "They're much more tolerant of human activity than we had ever imagined before," says Tom Logan, a biologist in Florida, which is home to a large population of bald eagles. "They're moving into developed areas with houses all around. What's happening is that, as younger generations hatch, the birds are imprinting on an environment that includes more development. This is the evolution of tolerance." What's more, if individual states fear that federal protections aren't sufficiently hawkish, they can always pass more restrictive laws on their own--an approach that can account for local biological conditions and development pressures.

Maybe that's what Philadelphia will do for those birds along the Delaware River. It might even help the city live down the notorious legacy of Benjamin Franklin, the Founding Father who believed that America's national bird shouldn't be the bald eagle ("a bird of bad moral character") but the turkey.