The forests of the Hawaiian Islands, home to the most endangered collection of birds in the nation, represent the most threatened habitat in the entire United States, according to a new report by the American Bird Conservancy.

Hawaiian forests once housed so stunning a collection of birdlife that it amazed early ornithologists. Birds feathered in rich yellows, greens, reds, browns and grays nested in treetops, on the ground, and in tree trunk cavities. They developed food specialties that included insects, seeds, leaves, nectar and even other birds. Early Hawaiians were so struck by their colors that they made vibrant royal capes and helmets decorated with the feathers.

But about half the forest bird species of Hawai'i are now extinct, and many of the remaining birds are endangered.

The Maui po'ouli may be the most recent extinction, disappearing within the past few months. After a heroic effort to capture the last three birds in the wild and bring them into cages for captive propagation, the one that was captured has died, and the others cannot be found.

"Hawaiian forests topped the list as the most threatened bird habitat, where 30 Hawaiian birds are listed under the Endangered Species Act as endangered or threatened by the U.S. Fish and Wildlife Service," the American Bird Conservancy said yesterday in a press release on its habitat report. "Rain forests in the Pacific Northwest and Alaska, Florida wetlands, longleaf pine forests in the Southeast, tallgrass prairies in the Midwest, sagebrush in the Intermountain West, coastal beaches, and seabird nesting islands were all among the most threatened habitats."

Across the country, many of the same factors are responsible for habitat decline, the release said.

"The primary causes for the loss of the 20 most threatened bird habitats include invasive species, sprawling development, fire suppression, agriculture, deforestation, poor habitat management, overgrazing, pesticides, and water diversion."

The decline in birds continues, despite significant efforts to preserve forest habitat by government agencies, private landowners and organizations like The Nature Conservancy of Hawai'i. One of the newest tools, now on several islands, is the watershed partnership, in which landowners, governments and nongovernmental conservation organizations team up to protect large sections of what is generally forest land.

But most surviving upland forests are still plagued by alien plants, mosquitoes carrying bird diseases, rats that eat chicks and eggs, pigs that dig up the forest floor and create mosquito habitat, and much more.

"Despite its unique flora and fauna and the high level of threats, Hawai'i ranks close to the bottom of the list of states for spending on fisheries and wildlife," the bird conservancy report says. The state is proposing dramatic increases in natural resources funding in this year's Hawai'i Legislature.

The San Diego Zoological Society's Keauhou Bird Conservation Center is raising several species for forest birds in captivity, but despairs it will have no secure place into which to release them.

"At the Keauhou Bird Conservation Center we work to save a number of bird species such as the 'alala and the Maui parrotbill," said center director Alan Lieberman. "Saving these species is important but meaningless if the habitats they come from are also not protected."

American Bird Conservancy President George Fenwick said birds play important roles in their ecosystems, and they also provide revenue from such things as wildlife viewing — which he said represents $43 billion in the U.S. economy with 66 million Americans participating.

"Millions of Americans love to watch birds, whether on organized outings or in their own backyards. Without action to conserve these dwindling habitats, there will be fewer and fewer bird species for everyone to enjoy."

Reach Jan TenBruggencate at jant@honoluluadvertiser.com.