The largest hawk in North America has been declared an endangered species in Washington state as fewer of them have been breeding in Benton and Franklin counties.
Friday the Washington state Department of Fish and Wildlife Commission voted unanimously to move the ferruginous hawk from the state’s threatened species list to endangered. status.
The change will bring more visibility toward the decline of the species, said Commissioner Kim Thorburn. It also could prompt more steps to protect the hawks.
The ferruginous hawks spend about a third of the year in breeding territories, with Benton and Franklin counties the core breeding area in Washington state.
The hawks seek out grasslands and shrub-steppe in Eastern Washington to nest and raise their young
“Ferruginous hawks have been in trouble for decades,” said Taylor Cotten, conservation assessment section manager at the Washington state Department of Fish and Wildlife, earlier this year.
The ferruginous hawks were common in the early 1990s in several Eastern Washington counties, according to a draft review of the hawks in Washington state released earlier this year by the Washington state Department of Fish and Wildlife.
A study in 1926 described many old nests made of sticks in the Kiona-Benton City area and said they were most common near the Columbia and Yakima Rivers.
But between 1992 and 1995 the average number of breeding pairs nesting in the state dropped to 55. The last statewide survey conducted in 2016 found just 32 breeding pairs.
“Between 1974 and 2016, there have been significant declines in nesting territory occupancy, nest success and productivity,” the draft review said.
Loss of prey, habitat
The decline in Eastern Washington has been driven by several factors, including the development of land in the Tri-Cities area.
Over half of Washington’s original shrub-steppe had been converted to agriculture land by 1986, leaving remaining habitat in fragmented segments, the draft review said.
Wildfires also have degraded habitat in Eastern Washington.
The loss of abundant jackrabbits and ground squirrels as prey for ferruginous hawks, not just in Washington state but also in their late summer and winter ranges, is likely a significant factor in the declining number of breeding pairs in Eastern Washington, the draft review said.
Ferruginous hawks are reddish brown, but their underside is white. As they fly overhead, the birds appear white with black markings, including “commas” toward the end of their wings. Heads are brown with creamy streaking.
Adults can be as large as 27 inches from top of the head to tail tip and the wingspan can be nearly five feet.
Most ferruginous hawks overwinter in California before migrating north in the spring to breed. They leave Eastern Washington in late July to spend late summer and fall in the southern Canadian provinces, Montana and western plains.
Wind turbines may have also played a role in the decline of breeding pairs, the draft review said.
Five ferruginous hawks are known to have died from turbine strikes along the Columbia River between 2003 and 2012, with that count likely low, according to the draft review.
Hawks and wind farms
One study found that the greater the density of wind turbines in north-central Oregon the lower the survival of young hawks in the area.
The Washington state Department of Fish and Wildlife raised concerns about ferruginous hawks and other wildlife in comments on the Horse Heaven Wind Farm proposed for Benton County that the agency submitted this spring to the Washington Energy Facility Site Evaluation Council.
Although most of the land for the proposed wind farm is on dryland wheat fields, many of the turbines, transmission lines and solar arrays are close to or cross over draws and canyons with shrub steppe and grassland habitats, the Department of Fish and Wildlife said.
In addition, the ridgeline of the Horse Heaven Hills is an important foraging area for raptors, it said.
The Horse Heaven ridgeline is among the last remaining functional and uninterrupted shrub-steppe and natural grasslands in Benton County, it said.
“Maintaining sufficient foraging area to support successful territories and nesting for ferruginous hawks and other raptors that use thermals and air currents associated with the Horse Heaven Hills seems particularly challenging with current proposed structure orientation,” Washington state Fish and Wildlife said in its comments.
Ferruginous hawks are not listed under the federal Endangered Species Act, but were listed as threatened as early as 1983 in Washington state. They also are listed as threatened in Canada.
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