Migratory birds<br>being studied

GCNP — A raptor migration study at Grand Canyon National Park reaches a milestone Sunday when the project enters its 10th year.

HawkWatch International, a nonprofit organization headquartered in Salt Lake City, monitors long-term trends in populations of raptors. Grand Canyon is located in the southerly portion of the Intermountain Flyway.

The red-tailed hawk is among the migratory species of birds studied.

"The 10 years there is really kind of a critical milestone for us," Paul Grindrod, outreach coordinator with HawkWatch, said in a telephone interview from his Salt Lake City office. "Ten years is considered the minimum amount of data you need to see significant trends. Now that we have that milestone, it gives us a more powerful statistical tool to look at data."

The organization will be conducting a study at Lipan Point for the 10th straight year. In 1997, a second site was added at Yaki Point.

"Our goal in the bigger picture is to have data over a long timespan and over a large geographic range so we can start comparing the trends that we see from place to place," said Grindrod, who added that HawkWatch runs an overall network of 15 sites. "That gives us another level of comparison."

Information gathered in the studies enables HawkWatch to better understand the life histories, ecology, status and conservation needs of raptor populations across the continent, Grindrod said.

Because raptors occupy large home ranges, inhabit most ecosystems and are sensitive to environmental contamination and other human disturbances, the studies serve as biological indicators of ecosystem health.

"We look at raptors as environmental indicators because they're top predators ... they occupy huge home ranges in a diverse range of habitats," Grindrod said. "By monitoring raptor populations at the larger level, what we're trying to do is get clues as to what environmental changes may be affecting populations."

During the 1999 season, observers counted 6,297 raptors of 16 species at Lipan Point and 5,420 migrants representing 17 species at Yaki Point.

"The raptor migration is a popular attraction," Grindrod said. "Many of the shuttle-bus drivers in the park are hawk enthusiasts and often come to the sites to get daily updates on the migration."

Two full-time educators man the Grand Canyon sites. Grindrod said public participation is welcomed by HawkWatch's migration sites.

The HawkWatch migration counts begin Sunday and will run through Nov. 5.