State officials have failed to prevent an endangered native bird from moving closer to extinction by not following court orders requiring the elimination of certain alien species on the slopes of the Big Island's Mauna Kea, environmental groups say.

The groups estimate that from 2003 to 2008, 60 percent — nearly 4,000 birds — of the entire population of the palila has disappeared from its habitat area, leaving behind about 2,640.

“;This downward trend is especially alarming,”; the groups said.

The state Department of Land and Natural Resources declined comment yesterday.

The groups, including the Sierra Club and Hawaii Audubon Society, filed a motion yesterday in U.S. District Court in Honolulu to enforce previous court orders to eradicate alien species, including goats and sheep, from the slopes.

The groups want the court to order the state to construct a fence around the palila's 34,350-acre habitat by June 1, 2011.

Earthjustice attorney Koalani Kaulukukui, representing the groups, said a 55-mile fence was built in the 1930s as a work stimulus project during the Great Depression, and a similar project could be done during this period of economic hardship.

The palila lives in Mauna Kea's dry-land forest, once composed mainly of thick stands of mamane and naio trees.

Goats and sheep have reduced the number of young native trees by eating their shoots and seeds.

Conservationists said the palila feeds on the seeds of the mamane trees and obtains additional nutrients from the mamane flower buds, the leaves and flowers of the naio, and other native plants.

Kaulukukui said the goats and wild sheep came from ranches in the area, and in the 1960s the state stocked mouflon sheep on the slopes.

Court orders in 1979 and 1987 barred the state from continuing to maintain any population of feral goats and sheep within the palila's federally designated critical habitat, conservationists said.

The court motion alleges the state began carrying out the eradication in the late 1980s and encountered success in improving the palila's habitat.

But state officials discontinued their eradication program in 1995, and the sheep population began to rise, prompting conservation groups to seek another court order in 1998, the court motion alleges.

The 1998 court order required the state to implement a program of public involvement in the eradication and also to conduct biannual aerial hunts.

The groups said a statistical analysis based on aerial hunting between 1998 and 2002 showed the presence of a growing sheep population, and the upward trend continued through 2008.

The groups said the Hawaii territorial government erected the 55-mile-long stock-proof fence around the Mauna Kea Forest Reserve in 20 months and removed 46,000 feral sheep and more than 2,200 other animals between 1937 and 1947.

It said portions of the perimeter fence stand today but are degraded and inadequate.