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After the elusive goshawk

The secretive, dive-bombing birds are making it tough for scientists to learn more about them

Posted: Sunday, July 15, 2001

Tracking Alaska's goshawks isn't easy.

In the 10 seasons the U.S. Forest Service and the Alaska Department of Fish and Game have been pursuing the birds, they've located about 60 nesting areas in the entire Tongass National Forest. By comparison, there are thousands of known eagle nests.

Goshawk research was inspired in large part by conservation groups in the Lower 48, which repeatedly petitioned to have the Queen Charlotte goshawk listed as endangered. Courts have yet to make a final ruling, but efforts to find out more about the elusive bird continue.

Even when a nest is found, approaching it can be tricky. Goshawks are quick to defend their territory and generally don't tolerate intruders.

"The females in particular are more defensive, more aggressive," said Craig Flatton, a Fish and Game biologist who has been working with the birds in the field since 1992. "They'll actually dive at people. People have been struck by their talons."

 

The birds display a range of defense behaviors. Some "make you get down, head behind a tree and duck," Flatton said. Others remain in the tree, sounding their distinctive "kak-kak-kak" defense call.

"It's almost like a personality thing," Flatton added.

Aerial attacks aside, the interagency project begun in 1991 has been no small feat. Using radio transmitters, Alaska researchers have tracked the habitat and behaviors of the Queen Charlotte goshawk, a subspecies of the more common Northern goshawk, which lives throughout the Pacific Northwest coast.

The Northern goshawk is a predatory bird, generally the size of a large raven, found in much of the United States and Canada. Thanks to its large home range and tendency to move around, the goshawk is the type of animal that can serve as an "umbrella species" in Alaska. Protection of such wide-ranging species through habitat management usually means its prey is protected as well.

But monitoring the goshawk has proven difficult. This is one factor in the winding down of the study taking place this year, said Kim Titus, regional supervisor for the Department of Fish and Game's Division of Wildlife Conservation. In addition, the study has amassed large amounts of data and time is needed to write it up.

The wind-down has led to some changes in procedure. While investigators have generally gone into the field in April and continued work until August, Flatton said work during 2001 will be concentrated in June and July.

"The goshawks are very secretive and wide-ranging, so the only way you can really study them firsthand is to find their nest sites," Flatton said.

To that end, much of the field work has involved finding nesting sites; now biologists will check known nests for habitation. The check is necessary because goshawks establish several nests in an area and move around depending on the year.

 

Another part of the research has fitted about 50 adult birds in Southeast with radio transmitters, allowing them to be tracked over wider areas. The tracking has led to some revelations about the amount of area covered by the birds during the breeding season, which lasts from March through July.

"Adult females' ... ranges across the Tongass average over 40,000 acres," said Titus. "Much larger than brown bear home ranges here."

No similar range studies have been conducted for other birds of prey, but Titus said the goshawk range during the nesting season could easily be larger than that of bald eagles. The ranges of individual birds are often far lower than the average, he added.

"We've had a number of female goshawks tagged on Douglas Island, and those female ranges during the summer from were 8 to 30,000 acres," Titus said. "There's a lot of variability in birds."

The project's initial goal was to assess the effects of logging and other forms of forest management in the Tongass on the goshawks. Though little was known about the birds, concerns about their numbers has been raised by groups in the Lower 48, which petitioned the U.S. Fish and Wildlife Service in 1991 to list the Northern goshawk for protection under the federal Endangered Species Act. Teresa Woods, field supervisor for the Fish and Wildlife Service Juneau said the petition did not apply to Alaska's goshawks, but the Forest Service and Fish and Game hoped to find out if continued monitoring of the birds was feasible.

 

Interest in Alaska's Queen Charlotte goshawks began to build in 1994, when the Southwest Center for Biological Diversity petitioned the Fish and Wildlife Service to list them as endangered. The Fish and Wildlife Service initially decided the listing was not warranted and the petitioners sued. In 1996, a judge ruled that the Fish and Wildlife Service should reconsider, a decision the Service appealed and won.

At present, the case has been returned to District Court and a new judge must now consider whether the Fish and Wildlife Service's ruling was a fair one. Titus said he agreed with the Fish and Wildlife Service's decision.

"My opinion is that these birds in Southeast Alaska do not warrant listing," Titus said. "However, they do warrant management attention in ensuring that wherever possible the Forest Service ensures habitats for them."

Don Muller, a board member of the Sitka Conservation Study, participated in the original effort to list the goshawk as endangered.

"In terms of the threat to the goshawk, it's still there," he said. "It's a hawk that requires very large ranges in the forest. It prefers old growth forest, and in the southern Tongass especially logging was destroying the habitat of the goshawk."

 

Information gathered from the study may make protection measures for the goshawk easier. Though many questions - such as the specific numbers and ages of birds in Alaska - remain unanswered, other areas have been thoroughly researched. A study by graduate student Steve Lewis shed new light on the eating habits of goshawks during the breeding season, and more information is now available on the goshawk's migration and nesting habits.

"There's a (common) statement out there that birds of prey mate for life," Titus said. "That's one of the myths that we've dispelled in this project. There's a very high divorce rate in goshawks - 30 to 40 percent per year."

The Alaska project is also the most comprehensive radio telemetry study of goshawks ever undertaken, Titus said. The work hasn't come cheap; Gene DeGayner of the U.S. Forest Service estimated the cost had reached $1 million.

"That's just a round number," DeGayner said. "But as far as a habitat study, it's clearly the most expensive study."

Work will continue even as the project winds down. The Forest Service and Fish and Game plan to fit 10 birds with satellite transmitters and continue to track their movements.

The new goal is to find another umbrella species that will be more feasible to monitor, Titus said.

"The question for me is, 'Can we find a surrogate for the goshawk that will tell us something about forests and forest management that would be less expensive to monitor?'" he said.



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