By Jan TenBruggencate
Advertiser Columnist

Some wildlife officials are hoping that controlling rats, which compete with Hawaiian forest birds for food, will prompt some of the birds to begin nesting year-round, or over a longer season, instead of just in winter.

Kamehameha Schools wildlife biologist Tonnie Casey said rats may compete for food so effectively most of the year that the birds lack energy to reproduce.

"If we get rats down to really low numbers, we may get nesting year-round," she said.

U.S. Fish and Wildlife Service biologist Eric VanderWerf is not so hopeful.

"Nesting is a big cost to the parents. It's a common pattern that birds time their reproduction to coincide with peaks in food availability. I kind of doubt that they would begin nesting at other times," he said.

However, controlling a major food competitor could make things easier. "It's possible they will increase the length of the nesting season, and we may see more nesting success," VanderWerf said.

Scientists will test the rat-control theory on a large chunk of koa forestation land owned by Kamehameha Schools. The 3,000-acre fenced section of Keauhou Ranch is between the 5,500- and 6,200- foot elevation on the slopes of Mauna Loa.

Rat control was temporarily stopped there recently after feral pigs began eating the rat bait and died. The pigs previously ignored the enclosed bait stations, but after they got a taste for the fish-flavored bait during air drops of unshielded bait pellets last summer, they began breaking into the sturdy bait containers.

"Pigs had been left in the area to see what would happen. We've learned now that we have to take the pigs out of an area if we want to use aerial bait distributions," Casey said.

Pigs are now being eradicated within the fenced area, and bait placement will resume in November.

"We will start rat control for the December bird nesting season," Casey said. "We'll keep it up until the young birds fledge" and are able to fly away and protect themselves from rats, who have been known to prey directly on eggs and young birds as well as compete for food.

Casey said the Keauhou Ranch acreage has a good collection of endangered and other native birds, including 'akiapola'au, Hawai'i creeper, Hawai'i 'akepa, 'elepaio, 'apapane, 'i'iwi, Hawaiian thrush or 'oma'o, Hawaiian hawk or 'io and Hawaiian goose or nene.

If you have a question or concern about Hawai'i's environment, contact Jan TenBruggencate at jant@honoluluadvertiser.com, (808) 245-3074, or P.O. Box 524, Lihu'e, HI 96766.