The new, interactive online atlas is considered the bible of Minnesota's native birds, documenting species that nest and raise their young in the state's forests, prairies, suburbs and cities.

Volunteers joined researchers from the University of Minnesota Duluth's Natural Resources Research Institute and Audubon Minnesota, fanning out across 2,353 townships — some 99.5 percent of the state.

They made more than 1 million bird observations, recorded 380,000 different contacts and confirmed 249 species as nesting across the state.

Work began in 2009 with major funding from the Minnesota Environmental and Natural Resources Trust Fund, state lottery profits allocated to natural resource projects. It took four years of field work and then another four years in the office to analyze the data, painstakingly separating good data from lesser stuff.

A nest with young or eggs got an absolute confirmation, males repeatedly singing might be a "probable" and birds hanging around a suitable habitat might be a "possible" or "observed." Whether they made the list of 249 depended on the species, said Jerry Niemi, ornithologist, senior program manager for the NRRI and a lead author of the atlas.

Birding experts followed up in virtually all areas to confirm what the volunteers found, said Lee Pfannmuller, ornithologist who helped head the project for Audubon Minnesota.

A comprehensive account of the status and distribution of Minnesota's breeding birds hasn't been compiled since 1936 when T.S. Roberts published his second edition of "Birds of Minnesota." But even Roberts didn't cover as much of the state.

"Nobody has ever done anything this comprehensive in Minnesota," Niemi said, noting field observers covered even huge roadless areas of the state like the Boundary Waters Canoe Area Wilderness and the Agassiz/Red Lake peatlands.

So far the atlas is only available online, but Niemi said preliminary talks are underway with the University of Minnesota Press to publish a hard copy. He said the value of the atlas will be more obvious in 20 and 40 years, when he hopes the next statewide surveys are conducted in the same way, to measure the progress and plight of Minnesota's birds.

As expected, the new atlas confirmed the success of bald eagles, osprey and peregrine falcons, all of which were in short supply when Roberts conducted his survey but which have rebounded beyond most expectations. Already in decline in the 1930s due habitat loss and indiscriminate shooting, those species nearly went extinct by the 1960s due to toxic pesticides.

"The raptors really are an amazing success story. Already by (Roberts') time they had been nearly shot out of existence. Roberts lamented how few raptors remained," Niemi said. "Their numbers went down even more due to DDT. But they have really become a conservation success story."

Minnesota now has nearly 10,000 nesting pair of bald eagles.

"I remember in the '70s when the U.S. Fish and Wildlife Service thought a good recovery goal would be 300 nesting pair of bald eagles in northern Minnesota. Now we have thousands all over the state," Pfannmuller said.

When Roberts compiled his treatise in 1932 he wrote that "the days of the trumpeter swan as a bird of Minnesota have long since passed." Now, Pfannmuller noted, thanks to reintroduction efforts by the Minnesota Department of Natural Resources, the atlas survey found an estimated 17,000 trumpeters across 72 of Minnesota's 87 counties with nesting confirmed in 55 counties.

Other species haven't done as well, especially those that thrived in prairie grasslands and hardwood forests, habitats that have declined markedly over the last 81 years as agricultural crops and development have spread. Species common in 1936 like the Sprague's pipit and chestnut-collared longspur "are almost gone now," Pfannmuller. Other species in big trouble compared to 1936 are the piping plover and the cerulean warbler.

Another, the baird's sparrow, "is gone," essentially extirpated. A dozen species Roberts found in 1936 were not found at all this time.

Pfannmuller said Roberts wrote glowingly about the wide distribution of the black-crowned night heron in wetland areas. "Now, even compared to the 1970s, we're not finding many at all," she said. "We don't know why."

But Pfannmuller said some new species are moving north across the state, some in response to a warmer climate. Red-bellied woodpecker, once seen only along the Iowa border, have now been confirmed nesting in Duluth and have been see as far north as International Falls.

"We're seeing more cardinals farther north than ever before, and the red-bellied woodpecker is moving north. ... Part of that is the warmer winters and part of it is backyard feeding," she said. "We've lost some species, we've seen some news species. ... I think, overall, Minnesota birds are doing pretty well."

For the birds

The website at mnbirdatlas.org includes an interactive map and can be searched by species. Each species has information on where it is found in Minnesota, population estimates and conservation efforts as well as history.