Michael Parr, vice president of the American Bird Conservancy, gazed into the trees on Roosevelt Island on a morning earlier this month as a warbling vireo sang away.

“Jonathan, do you think that’s the least interesting looking bird in North America?” Parr asked novelist Jonathan Franzen, who was standing beside him. “It’s certainly on the list.”

A debate ensued over the small gray creature perched atop a branch, a species the Cornell Lab of Ornithology calls, unkindly, “a drab bird of riparian woodlands.”

“Yes, along with the orange-crowned warbler,” Franzen replied.

Parr agreed. “It’s false advertising,” he said. “You can never see the crown.”

Spring bird migration has just finished peaking along the East Coast, bringing striking and unimpressive species alike as they make their way north. The pathway they navigate has become increasingly perilous, as factors ranging from illuminated buildings to wind turbines exact a toll.

“It is literally a commando course for these birds to navigate through, and we’re making it worse,” Parr said, walking through one of the places to spot birds during their spring flyover. Along with Rock Creek Park, Washington’s Theodore Roose­velt Island offers respite and foraging grounds for migrating birds.

Federal officials and conservationists are trying to reduce the threats the birds face and appear poised to make major gains on the most basic of avian obstacles: commercial and residential build­ings that get in their way.

Building windows and those that are lit at night kill hundreds of millions of birds in the United States annually, according to experts. The American Bird Conservancy estimates that glass accounted for between 100 million and 1 billon bird deaths in 2006, while urban light killed at least 31 million in 2009.

In the case of glass, birds often either fail to see it or are disoriented by its reflectivity. Illuminated buildings, by contrast, attract birds when the surrounding area is dark.

The only other threat that exacts a similar toll on birds is cats, which kill between 500 million and a billion of them a year.

Anne Lewis, president of the D.C.-based City Wildlife, said the battered birds she and other volunteers collect at the foot of the city’s buildings during their early-morning walks belong to some of North America’s most imperiled species. Last year her group found 89 dead and 35 injured birds near edifices including the Convention Center and the Thurgood Marshall Federal Judiciary Building.

“We’re not talking about common birds. What we’re finding are the beautiful migrants, the songbirds in decline,” said Lewis, who helps lead expeditions during the spring and fall migration seasons. “We’re going to need every one of these birds to breed if we’re going to keep these populations from decline.”

The lights are now out in the Marshall building’s atrium each night, according to a spokeswoman for the Architect of the Capitol, and the office is working with the Administrative Office of the U.S. Courts to develop a long-term solution that will address both the collision risk and building security.

State and city officials across the country are considering imposing bird-friendly building ordinances, along with policies that would shut off lights on tall buildings at night.

“I think we’re on the verge of a tipping point,” said Christine Sheppard, the collisions campaign manager at the American Bird Conservancy.

Nine U.S. cities and Minnesota have launched programs to darken commercial buildings after hours. In other cities —including the District and Baltimore — groups are preparing to campaign for similar measures.

In many cases, these initiatives are voluntary. Bill Stewart, conservation chairman of the Delmarva Ornithological Society, used federal funds aimed at reducing carbon dioxide emissions to launch “Lights Out! Wilmington” last month at the start of the spring migration season. The organization wants the operators of 20 of Wilmington’s tallest buildings to go dark between 10 p.m. and dawn for 117 days a year, and three have already agreed. If all 20 buildings cooperate, Stewart estimated, it would cut the city’s carbon output by 1.2 million tons a year.

Minnesota mandated that between March 15 and May 31 and Aug. 15 and Oct. 31, occupants of state-owned or state-leased buildings must turn off building lights between midnight and dawn, as long as the building isn’t normally used during those hours.

Designing a building that’s less likely to prompt bird strikes can include a range of measures, including reducing the overall amount of exterior glass; reducing the reflectivity of the glass; and limiting the exposure of glass at lower levels.

In some cases, these efforts have encountered resistance. The California Building Industry Association has opposed two separate proposals aimed at establishing a statewide bird-friendly building code. Bob Raymer, the organization’s engineer, said that although the initiatives are “well-intentioned,” the proposals that have come before the state’s Building Standards Commission have been too vague and posed conflicts with existing state fire and energy-efficiency requirements.

The commission needs to “work the bugs out” before it can adopt statewide requirements, Raymer said, adding that he expects some sort of bird-friendly guidance will eventually pass. “This issue’s not going away,” he said.

The energy industry is emerging as a new avian obstacle. Raptors and other species are getting caught in the blades of wind turbines along their routes, while natural gas exploration in Appalachia is fragmenting habitat prized by the cerulean warbler, the fastest-declining migrant songbird in the United States. Franzen wrote about the cerulean warbler in his latest book, “Freedom,” exploring how the needs of a single species can clash with the nation’s drive for energy production.

On a recent morning in the District, Franzen and Parr were intent on spotting other migrants, such as an indigo bunting whose call rang out from the woods on Roosevelt Island.

“Let’s get that bunting,” Franzen declared. “This is the most electric blue bird.”

The bunting did not appear. But the blackpoll warbler did, resting in plain sight before heading north for the summer.

“It’s sort of a sad thing when you see the blackpoll warbler,” Franzen reflected, noting that the songbirds were on their way. “They’re the rear guard among the migrants.”