Sometimes the best lessons take place outside the classroom. A group of Washington, DC, third graders learned that recently during a lesson on just how connected the world is — and how essential their city’s trees are to a musical little bird that spends half of its life thousands of miles away.

Huddled around a map spread on the hallway floor, about a dozen students at John Eaton Elementary School quickly identified the United States and a handful of its neighbors to the south, including Mexico, Panama, Costa Rica and Honduras.

“Does anybody here have parents from El Salvador?” asked Steve Dryden, a guest presenter at the school that day.

With a little prodding, Raul Hernandez Aguilar shyly raised his hand. His parents are from the Central American nation, he said, and he was born there, too.

With that, Dryden launched into an explanation of how a diminutive songbird, no bigger than a robin, makes the same journey across the Gulf of Mexico to the nation’s capital that Raul and his parents did years ago. Only it flies that route every year to announce — more loudly than the imported cherry blossoms — the arrival of spring.

Did the students, Dryden asked, know that their city also has an official bird?

“It’s the wood thrush!” a few of them exclaimed in unison.

“That’s right,” said Dryden, who is director of a multi-year initiative to plant trees in Rock Creek Park and engage the nearby Latino community. He’s reached 165 students through presentations like this at area schools over the last three years.

The District gets its share of migratory bird species, but this thrush — with the help of people like Dryden — has become a particularly eloquent advocate for the urban tree canopy that helps sustain it.

“The wood thrush is a really special bird,” Dryden told the children, “because this bird actually flies here every year to be our bird.”

It’s in need of help, however. Though still relatively common, wood thrush numbers have declined in recent decades, in part because the U.S. Eastern forests where it nests for six months a year are being fragmented. Dryden, with help from several nonprofit groups, is trying to broaden awareness of the vital connection between the songbirds that frequent DC’s Rock Creek Park and the trees that support them.

Dryden, 62, worked as a journalist in the DC area for 20 years before he made the switch to environmental work, much of it for Audubon Naturalist Society, based in Chevy Chase, MD. He first ran across the wood thrush in the society’s journal, which was named for the bird at the time. Dryden looked the species up, only to realize he’d been hearing the wood thrush’s signature ee-oh-lay call since childhood while growing up in Arlington.

“It’s the kind of call you never forget once you hear it,” he said.

But hearing is not necessarily seeing. Though he’s worked on habitat restoration and education surrounding the thrush for nearly 20 years, Dryden can’t be sure he’s seen one. He even went to Belize last winter to try spotting the shy bird in its southern habitat.

“I was with a guy and he pointed it out to me, but I don’t think I really saw one,” said Dryden, who admits he doesn’t have the patience to be a good birder. “I know I haven’t seen one in Washington.”

But he has heard the birds’ trill plenty of times, and is working to ensure the next generation will, too.

Audubon Toyota Together Green, a joint program of the National Audubon Society and the Japanese automaker, provided seed money three years ago for Dryden’s traveling lessons on the birds. Since then, he has also partnered with organizations like Casey Trees, the National Park Service and the Alliance for the Chesapeake Bay to plant or protect more than 300 native trees in areas of the park and near the schools.

Dryden’s educational visits are concentrated at schools in Washington’s Mount Pleasant and Columbia Heights neighborhoods, where many of the students are from the Central American countries that are the songbirds’ winter habitat.

Later this year, Dryden plans to reach out to their parents through a traveling exhibit on the thrush. By talking to Latino immigrants about the birds that migrate to and from their home countries, the project aims to engage more of them in the preservation of key habitats both near and far.

Protecting and adding new trees in an urban setting is a boon for the Bay as well as the birds. Trees help absorb runoff in an otherwise concrete oasis, filtering it before it reaches tributaries. They also clean the air, beautify neighborhoods and, one study found, even lower crime. The Chesapeake Bay Watershed Agreement adopted two years ago calls for increasing the urban tree canopy by 2,400 acres across the district and the six states that drain into the Chesapeake.

Still, not every city dweller appreciates their environmental benefits. Some homeowners might prefer a sunny lawn, or view big, mature trees as threats to roofs, fences and vehicles — or they would like to eliminate the mess created by bird droppings.

But native trees are key to the survival of the wood thrush and its feathered friends. Oaks host, in more abundance and variety than their nonnative counterparts, the caterpillars and insects needed to support a growing brood during nesting season. Native oaks harbor around 530 species of insects, almost 100 more than the next best backyard tree, according to Doug Tallamy, professor of entomology and wildlife ecology at the University of Delaware.

During his presentation to the children, Dryden passed around an illustrated book of the tropical environments where the wood thrush winters — with several of its “bird friends” pictured as well. He asked the students why they thought the bird would ever want to leave such a paradise. Does it look a little crowded, like there might not be enough food? Why would they need more food?

“Um, for having babies?” offered Isabella “Izzy” Oh.

“That’s right,” he said. “And those baby birds need lots of ‘bug food,’ and by extension, lots of trees.”

After the geography lesson, Dryden took the children outside to see a few of the trees he and other students helped protect. As he tells it, Dryden couldn’t help but act when he saw that several of the best specimens of bird-supporting trees — oaks — had been chopped to stumps on a residential street a block from the school.

Dryden built wire cages around the stumps, which were now sprouting sturdy saplings. Students from another class had written signs: “Please don’t bother the trees. The birds need them.”

Inspired by the sight, third grader Camden “Cam” Gorman suggested: “What if we put signs on oak trees all over town saying, ‘Protect these oaks. Do not cut them down.’ Do you think that would work?”

“Yes,” Dryden said, smiling. “That would help.”

On the walk back to the school, where the students got to listen to a recording of the wood thrush’s iconic trill, enrichment coordinator Eileen Langholtz, who also runs the school garden, shared another idea with the students. “In our pollinator garden, maybe we should plant an oak tree.”