WASHINGTON, D.C.—The National Mall here attracts millions of tourists each year, drawn by the sweeping views of the U.S. Capitol and the Washington Monument, as well as the world-class Smithsonian museums flanking the grassy expanse. But earlier this week, an unusual sight greeted some visitors: a small team of scientists setting up nets to capture some of the mall’s flying residents.

Their quarry—including gray catbirds, song sparrows, and mourning doves—were soon released. And the unusual pop-up field station also aimed to draw attention to a landmark anniversary in bird conservation, as well as an upcoming conclave on bird science.

The conclave is the North American Ornithological Conference, a major meeting set to open here on 16 August. On the same day, bird lovers will be celebrating the 100th anniversary of the Migratory Bird Treaty Act, a 1916 agreement between the United States and Canada that is considered a historic turning point in international efforts to protect birds.

The treaty, spurred in part by warnings from ornithologists that unregulated hunting was decimating many North American bird populations, played an important role in catalyzing conservation efforts in the early 20th century, says Pete Marra, head of the Smithsonian Migratory Bird Center in Washington, D.C. Mexico ultimately joined the pact, and the United States struck similar deals with Russia and Japan to collaborate on protecting birds that roam across borders.

Now, such international collaboration is needed more than ever, as dozens of species of migratory birds face dramatic population declines, Marra told reporters during the 3 August bird netting event on the mall. “Some of these populations have declined by up to 90% … and it is going to take efforts in [many nations] to restore them,” he says. Some migratory birds alight in six or more nations during a typical year, scientists note, meaning that no one country can adequately protect them.

But figuring out exactly where migrating birds are facing their biggest threats can be a challenge, Marra says. For some, it might be habitat loss in their summer breeding grounds. Others may be threatened by changes in wintering areas. It would be a waste of time and money, Marra noted, to focus conservation efforts in the wrong places.

To prevent that, Marra’s center and numerous other scientists have been trying to better map bird migrations and understand habitat use patterns. One bright spot, sure to be discussed at next week’s ornithology conference, is the rapid improvement of microelectronics. That’s enabled the construction of small, lightweight tracking devices that can be strapped on even tiny birds, revealing exactly how they traverse vast distances.

Marra showed off some of those tiny tags at the mall event—and even helped strap one on a catbird (Dumetella carolinensis). The handsome, slate gray relative of the northern mockingbird was one of several birds that Marra’s research team had caught in the nearly invisible mist nets the researchers had erected in a quiet garden near the Smithsonian headquarters building. The catbird squawked and fluttered as the researchers carefully weighed and measured it, then put colored bands on its legs. As soon as it was set free, the bird dashed for a nearby bush, stopping only momentarily to turn and chew out its jailers with a sharp, raspy call.

Ultimately, the catbird and the other birds banded on the mall may add new details to the emerging portrait of bird migrations. It’s a field that keeps delivering surprises, Marra says, as tags reveal migrating birds making unexpected stops, remarkably fast flights, and taking astonishing detours.

“We’re really just beginning to understand many migrations,” he said as his team rolled up their nets and put away their banding gear. The big challenge, he suggested, will be figuring out how to quickly transform new scientific findings into effective action to save migratory species—just as the foresighted negotiators of the Migratory Bird Treaty Act did a century ago.