State of the birds: Mixed

Several major bird populations have plummeted over the last four decades as development transformed the nation’s landscape, but conservation efforts have managed to stave off potential extinctions of others, according to a comprehensive survey released Thursday by the Interior Department and outside experts.

“The State of the Birds” report, a sweeping analysis of data compiled through scientific and citizen surveys over the last 40 years, shows some species have made significant gains even as others have suffered.

Hunted waterfowl and iconic species such as the bald eagle have expanded in number, the report found, while birds along the nation’s coasts and in its arid areas and grasslands have declined sharply.

“Just as they were when Rachel Carson published ‘Silent Spring’ nearly 50 years ago, birds today are a bellwether of the health of land, water and ecosystems,” Interior Secretary Ken Salazar said in a statement.

“From shorebirds in New England to warblers in Michigan to songbirds in Hawaii, we are seeing disturbing downward population trends that should set off environmental alarm bells.”

The fact that concerted conservation efforts have saved birds such as the peregrine falcon and allowed various wetland birds to flourish, scientists said, shows that other species can reverse their declines with sufficient support from federal agencies and private groups.

“When we try, we can do it,” said John Fitzpatrick, executive director of the Cornell Laboratory of Ornithology. “There are now populations and habitats across the country begging for us to do it.”

The species in decline are being affected by climate change, habitat destruction, invasive species and disease, among other factors, the report found. More pedestrian threats, such as collisions with buildings and attacks by feral cats, have diminished birds’ numbers in some urban and suburban areas.

Hawaii, more than any other place in the country, highlights the challenge faced by native American birds. Seventy-one bird species have disappeared since humans populated the Hawaiian islands in 300 A.D., and 10 more have not been spotted in years.

At the moment, more than a third of the bird species listed under the Endangered Species Act are in Hawaii, but state and federal agencies spent only $30.6 million on endangered birds there between 1996 and 2004, compared with more than $722 million on the mainland.

“In Hawaii we’ve got lots of imminent extinctions, but not enough resources being spent on them,” said George Wallace, vice president of the American Bird Conservancy.

With sufficient funds, Wallace argued, federal managers could restore Hawaiian birds’ habitat and protect them against introduced species such as pigs, sheep and deer that threaten their survival. He estimated it would cost roughly $15 million to erect extensive fencing for the Palila, a Hawaiian honeycreeper whose numbers declined from 6,600 birds in 2003 to 2,200 in 2008.

Elsewhere in the country, conservationists are trying to protect rare bird species before disease can strike. On Santa Cruz Island, off the Ventura County coast, Nature Conservancy officials are conducting a vaccination campaign aimed at protecting the Island Scrub-Jay from the West Nile virus, which has already hurt some related bird species on the mainland.

Scott Morrison, the conservancy’s director of conservation science in California, said his group has determined the virus has yet to infect the island’s unique, bright blue birds even as incidence of West Nile among birds in Ventura County nearly doubled from 2007 to 2008. While the scrub-jay’s remote location offers them some protection, vaccination offers even more.

“There’s evidence, anecdotal, this [vaccination] could actually be a useful strategy to guard against this disease,” Morrison said, noting that scientists had already vaccinated California condors against the virus. “If it comes over tomorrow, maybe we would avoid some of these scary drops in numbers, for at least a subset in population.”