The Hawaii state bird is an endangered species, constantly threatened by mongooses, dogs, rats and other introduced animals even as they cope with the loss of grasslands and forests to development.

But the nene goose has found a safe home among the green golf course fairways and ponds of a Kauai resort, and they are thriving — exploding to some 400 today from just 18 birds in 1999.

In fact, the population at Kauai Lagoons has grown so much, the geese are now considered the threat. They pose a public safety hazard to the commercial airliners taking off and landing at the airport next door, forcing the state to scramble to devise a plan to move them somewhere else.

“With the numbers that are nesting, it’s just like, boy, there are going to be more and more birds there,” said Paul Conry, administrator of the state Division of Forestry and Wildlife. “If we don’t take action now, they will even get higher and higher in the future.”

The black-and-beige-feathered nene is unique to Hawaii but is believed to have descended from the Canada goose. It grows about 2 feet long and is the state bird.

Already, Hawaii’s state Department of Transportation spent $417,000 this fiscal year to have workers chase birds — mostly nene — away from the path of airplanes in Lihue 12 to 14 hours a day, seven days a week. That’s more than the $393,000 it spent to scare birds at the much larger Honolulu Airport, which has more than twice as many flights as Lihue.

Exacerbating the problem is that some golf course holes favored by the geese are not just next to the airport, but also squeezed in between a V-shaped angle formed by two runways. Between 2008 and 2010, officials reported seeing nene more than 5,000 times at the airport. Most of them were at the southern end of one runway, a critical area for airplanes landing and taking off.

Citing the public safety threat, Gov. Neil Abercrombie signed in April a proclamation suspending some state laws to enable the administration to swiftly move all the nene out of Kauai Lagoons.

Even so, it’s expected to take five years to finish the job in part because the birds don’t congregate at the resort unless it’s breeding season, which generally starts in October and goes through March. This makes it difficult for the animals to be rounded up. The state also needs to find new, safe homes for the birds.

The state captured and moved 10 of them to Maui after the proclamation was signed April 14, but that was all it was able to do so far this year, Conry said.

The state plans to take the geese to other islands that already have nene.

The most important need for the birds in their new homes will be protection from predators, Newman said, saying that the main reason nene thrive at Kauai Lagoons is because mongooses haven’t become established on Kauai.

The nene was almost wiped out, with the total population numbering just 30 by 1952. The number has since rebounded to nearly 2,000 thanks to scientists who have bred them in captivity.