WAIMEA, Hawaii — Bird calls ricochet among the trees in a patch of native forest on Mauna Loa's lower slopes, but the birds themselves are so evasive we sometimes spend minutes scanning the towering koa canopy to glimpse even a flicker of their small shadows.

A phalanx of binoculars goes up as a far-off silhouette wings closer and lands on a high branch overhead. The bright red bird with a slender, curved bill, an i'iwi, matches the coloring of the pom-pom-shaped lehua blossoms whose nectar it sips. The i'iwi perches for less than a minute, then launches off the branch and flits out of view on its black-edged wings.

I'iwi birds are common during winter when lehua blossoms flower on the ohia trees in this kipuka, a tract of Hawaiian forest protected from marauding herbivores by an old lava flow, said our birding guide, Garry Dean.

"In winter there are so many of them flying around, that's when they become 'trash birds,' " Dean said. "But today they are one of our target birds."

Dozens of bird species once filled the formerly thick forests of the Hawaiian Islands before logging, cattle ranching and feral animals introduced in the past two centuries — such as European boars, sheep and goats — razed and uprooted most of the birds' habitat.

But now 28 percent of Hawaii's 93 native bird species are extinct and another one-third are listed on the federal threatened and endangered species lists, according to figures released in 2000 from the U.S. Fish and Wildlife Service.

The Hawaiian Islands harbor 317 of the nation's 1,264 endangered and threatened plants and animals, according to the agency's latest figures from this year. More than half of the 31 avian species on the list from Hawaii are small forest birds.

Today the novice Hawaii birdwatcher is wise to use a guide to search for these rare and hidden soloists. Fumble with a birding guidebook and you risk missing the multihued creatures, many of which stand just a few inches high and tend to hop quickly and sporadically among the leaves.

Dean has led birdwatching groups for about four years with Hawaii Forest and Trail on the Big Island. He recognizes a variety of Hawaiian bird calls and can identify a species by its characteristic movements, talents that come in handy when a bird is backlit by the midafternoon sun or partially blocked by foliage.

The nature tour company's Rainforest and Dryforest Birdwatching Adventure begins at the western end of the serpentine Saddle Road, so named because it traverses the saddle between the massive volcanic peaks of Mauna Kea (white mountain) and Mauna Loa (long mountain).