Researchers warble for warblers.

Byline: Susan Palmer The Register-Guard

McKENZIE BRIDGE - It's a faint sound at first, a quick trill of notes followed by a buzzing higher note: the sound of a hermit warbler, a smallish, yellow-headed songbird that makes its home in the canopy of mature Douglas fir stands.

David Fields is listening intently for the sound in a small clearing in the woods behind the McKenzie District Ranger office in the Willamette National Forest.

A biology student from Wichita State University in Kansas, Fields is doing research here this summer, part of a national multiyear bird survey that will help scientists determine the overall health of five forest species.

National surveys suggest that these birds - the hermit warbler, Townsend's warbler, olive flycatcher and two species of hawks - may be in decline. Learning more about them now will help foresters manage the land better to keep the birds from becoming threatened or endangered later, said Willamette National Forest biologist Ruby Seitz.

The research is a joint effort among the National Forest Service, the Cornell Lab of Ornithology and the Student Conservation Association.

But funding for the study is scarce and Fields can't do all the surveying himself, so he's put out a call for volunteers who can spare some time to get trained and to make at least two visits to survey sites in the woods this summer.

On Friday, Fields demonstrated the technique as a rainy morning turned into a sunny afternoon in a clearing overgrown with bracken ferns and the tall spikes of blooming foxglove.

He played a CD of the distinctive calls of the five species, starting with the olive fly-catcher. After a couple of minutes of playing the tape, Fields listened for similar sounds coming from the surrounding fir and western hemlock.

Then he moved on to recordings of the other bird calls, interspersing periods of the tape with periods of quiet. After about 45 minutes, he had distinctly heard just the hermit warbler, the trilling calls coming from two places high up in the trees.

At the end of the session, Fields played one last recording, a "mob call" of pygmy owls and chickadees, the kind of sound that often prompts birds to fly out to investigate and defend their territory.

At this particular spot, the mob call recording drew lots of vocal responses from birds invisible in the branches soaring 100 feet overhead.

But the elusive fliers stayed put, and at the end of the session, Fields marked only the hermit warbler calls on his survey sheet.

About 20 volunteers have already signed on to help with the survey at 60 to 70 sites throughout the Willamette National Forest, and Fields said he hopes another 10 will sign up.

Volunteers need to commit to a training session and two forest visits; one by July 1, the second within two to four weeks of the first visit. Each session takes about 45 minutes.

Learning the distinct sounds of each of the birds may take some additional time listening to the CDs, Seitz said. The district office has extra boom boxes for those who need them.

People with some experience bird watching make great volunteers, but neophytes can help, too, Seitz said.

"For those with no experience, it's great way to learn about birding," she said.

BIRD RESEARCH

To help: Call David Fields, 822-3381, or e-mail him, [e-mail].

First training session: Sunday at 10 a.m. in Alton Baker park's picnic shelter

To learn more: Visit the Cornell Lab of Ornithology Web site at www.birds.cornell.edu

CAPTION(S):

U.S. Forest Service intern David Fields uses a CD player to broadcast bird sounds into the Willamette National Forest near McKenzie Bridge. At first, he plays the songs of birds he is attempting to study. He then plays the sounds of potential predators in the hopes of drawing responses. Fields surveys the forest canopy for sightings of the birds he hears.