Hawk population seems to be lagging

Ferruginous hawks, the largest soaring hawk, appear to be continuing to decline in Eastern Washington.

Washington Department of Fish and Wildlife biologists who conducted surveys this spring of known nesting territories counted fewer occupied nests than in 2002-03, the last year an extensive survey was conducted.

Because of budget constraints, biologists this year were unable to repeat the firsthand inspection and aerial surveys of nesting sites that they conducted in 2002-03. Instead, they relied on personal observation of known nesting sites of ferruginous hawks, which are listed as a threatened species in Washington and a federal species of concern.

On the Hanford Reach National Monument, no ferruginous hawks were counted at the 10 known nesting sites, said Heidi Newsome, biologist with the U.S. Fish and Wildlife Service’s Mid-Columbia National Wildlife Refuge complex.

Loss of shrub-steppe habitat to development and a resulting drop in prey species for ferruginous hawks — including ground squirrels and black-tailed jackrabbits — have contributed to their decline in Eastern Washington, according to a Department of Fish and Wildlife study conducted more than seven years ago.

Ferruginous hawks, which have a 4-foot wingspan, are sensitive to disturbance from humans and have been known to abandon nests if human activity becomes too much for them, Livingston said.

The survey found about 25 percent of the 200 known ferruginous nesting territories were occupied in most years in Eastern Washington, and many of those sites had been vacant for years.

“The ecology of this hawk, more than any other Buteo (soaring hawk), is dependent on the native prairie ecosystems that are becoming increasingly rare and fragmented largely due to conversion to agriculture,” the study said.

In Eastern Washington, ferruginous hawks build their nests on rock faces, in isolated trees, in the middle of a small grove of trees or on electrical transmission towers. Their territory ranges from Canada into 17 states, and they migrate.

Ferruginous hawks that nest in Eastern Washington typically fledge their young in June. Then some migrate east of the Rocky Mountains to follow prey, according to a 2003 migration and winter range study of the hawks by the Department of Fish and Wildlife.

That study also found that some wintered in California.

One anecdotal sign of their relative scarcity in Eastern Washington comes from Blue Mountain Wildlife, a Pendleton, Ore.-based nonprofit raptor rescue and rehabilitation group.

“We hardly ever get a ferruginous hawk,” said Lynn Tompkins, co-director. “We’ve had only a handful in 20 years.”