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Making green skies safer for raptors

Posted by: Bettina Woodford, Communications

Video produced by Ryan Hawk/Woodland Park Zoo.


A delicate spring dew has settled on the shrub steppe of the Columbia Basin. Raptors, migrating through the Pacific flyway from distant wintering grounds, have alighted here, driven by eons of instinct to breeding areas where a potential buffet of small mammals, such as ground squirrels and pocket gophers, awaits. Heeding the juveniles’ endless squawks, for several weeks dutiful parents will bring meat, day after day, for gaping beaks to tear into. The raptors’ main business here is to raise healthy young and ready them to fledge, egging the species on one season at a time. 

Fewer prey scurry about this landscape today, however. As ranches, farms, towns and paved roads have grown in number, more than 50% of previously undeveloped shrub-steppe habitat, a raptor haven, has disappeared. This hybrid environment makes survival harder for the large, long-lived birds at the top of the food chain. Now, a new kind of development has arrived: wind farms. More than 2,000 turbines spin out electricity in the basin landscape as Washington state looks to sustain growth and mitigate climate change by increasing reliance on green and renewable energy, a laudable goal. As they proliferate, so do concerns about losing breeding raptor populations. “We need to understand the cumulative impacts of wind energy projects on nesting raptors, including their potential displacement and collisions with the 100-150 foot-long turbine blades so we can better protect them,” says Jim Watson, a veteran wildlife research scientist with the Washington Department of Fish and Wildlife (WDFW).

Photo by Ryan Hawk/Woodland Park Zoo.

To achieve that goal, Jim looks to Woodland Park Zoo for help. Each spring, raptor keepers Gretchen Albrecht, Susan Burchardt, Ros Bas-Fournier, Joanna Bojarski, and Jean Ragland migrate to the basin too, providing him expert knowledge and research skills. They are the heart of a 14-year collaboration with WDFW, a Woodland Park Zoo Living Northwest project called Raptor Ecology of the Shrub-Steppe. For the last three years, they have focused on the effects of wind power on ferruginous and Swainson’s hawks at high-density wind farm sites in south-central Washington and north-central Oregon. Zoo researchers closely monitor hawks’ use of nesting ranges, flight patterns, and interactions in turbine collision zones.

Bumpy travels

Slightly winded, raptor lead keeper Gretchen Albrecht edges up the branches of a juniper tree as the sun arms the air. She is confirming the status of a particular nest, one of several the keepers focus on to track whether ferruginous and Swainson’s hawks are returning to this range annually, or are being displaced by the turbines and moving on to safer territory. Peering from a safe distance, she spies two large eggs. It is a bittersweet find. Indeed, the hawk pair had returned to their range and was preparing to raise this season’s young, taking turns sitting on the eggs and feeding on a dead vole one of them had hunted nearby. But Gretchen and Jim already know that the father, a banded Swainson’s hawk in their study, has been killed. His right wing shattered by a spinning blade, he lay slumped several yards away between his nest and a nearby turbine. His mate has already abandoned the nest. She is unable to hatch two eggs, feed ravenous chicks until they fledge and feed herself. Not alone.

Male Swainson’s hawk #39425 and the turbine that eventually struck him. Photo by Jim Watson.

With such keen eyesight, why do hawks not see these giant fans in their workaday flight paths?  Gretchen explains that “hawks are predators. After a long migration, their job here is straightforward, driven by instinct: build nests, find food and defend territory in the home range.” Making sense of strange, new human-built hazards is a secondary priority. “As Jim sees it, imagine waking up every day with hungry kids to feed. A huge, dangerous blender is lodged between your bedroom and your kitchen. Your eyes scan the ground, locking in on food, so even with all your flying skills, eventually you’re going to bump into it.”

Raptor traps?

The few years since turbines began appearing in raptor country equate to about a millisecond in evolutionary terms. Whether raptors will learn, individually and as a species, to navigate them better is an open question. Through focal observations, the keepers collect data on specific birds’ range behaviors, recording flight type, duration of interaction with or near turbines, and wind and turbine speed. They seek to discern patterns and trends holistically on two levels. The landscape level looks at whether populations are displaced by the turbines, abandoning their breeding grounds for safer but often less suitable habitats. The interaction level looks at whether the hawks become habituated to the turbines, flying near or through them.  In nesting territories, the mean rate at which hawks encounter turbine collision zones, a 400-foot radius around the blades, is once every 76 minutes.

Photo by Ryan Hawk/Woodland Park Zoo.

At 400 feet tall, a turbine rises to the same height at which hawks circle as they seek prey. The danger is in the blades’ rotational dynamics—slowing down, speeding up, stopping—especially at the outer tips. Even at a moderate revolution, those tips can exceed speeds of 150 miles per hour, creating whirls of air that can knock birds off balance, or suck them in, resulting in fatal strikes. In the U.S., estimates are that wind farms kill between 150,000 and 500,000 birds a year. Compared to the hundreds of millions of birds killed by vehicles, buildings’ glass windows and domestic cats annually, the number is relatively low. 

But wind farms are not just here to stay; they are here to multiply. According to researchers at MIT and the Santa Fe Institute, renewable energy patents now outpace patents for fossil fuels. That pace impacts birds and other wildlife. As with hawk #39425, “it’s hard not to have a visceral reaction to individual bird strikes,” says Jim. “But we really need to help wind companies and energy consumers grasp the potential population-level effects, particularly for endangered or threatened raptors. The more we understand their ranging habits and response behaviors to risk factors, the better we can sustain these valuable species over generations.” Preliminary results, to be released this year, suggest that these hawks continue to return to wind project areas to nest, although ferruginous hawks, more sensitive and in decline, are at greater risk of nest-site attrition. Their ranges span large, patchy networks of feeding areas across the basin, so their chances of interacting with turbines increase.

Keepers’ field work tools include Global Positioning Systems technology, telescopes, binoculars, photography, highly skilled eyesight and lots of patience. Photo by Ryan Hawk/Woodland Park Zoo.

Although only a few of the studied birds died from blade strikes, the population experienced considerable mortality from other human-related factors, such as poaching. Fine-scale analyses of flight patterns suggest that nesting hawks regularly pass through or around operational turbines on their territories, but may be learning to adjust their flight behaviors near turbines depending on wind speed. The study’s findings will improve state policy guidelines for safer turbine siting, operational regulations and bird-strike mitigation, and may even inform the industry’s research on blade design. While just about any human endeavor we undertake impacts the environment, green technology especially, through innovation and cooperation, can seek to reduce its impact on the habitat it occupies.

Safer skies

Back at the zoo’s Raptor Center, Gretchen wraps up a typical day. Feeder crickets chirp noisily in the background as she reflects on the field work stories she and the keepers tell curious zoo visitors during the popular flight programs. Children’s faces flush with awe and wonder as the birds cruise over the grassy knoll, showing off a magnificent portfolio of broad wings, strong talons and laser-sharp focus. Gretchen knows that the more people connect to the zoo’s field projects, the more conservation action they will take. Most visitors are shocked to learn that turbine blade tips can slice the air so fast, and are moved to learn how raptors are so deeply connected to the basin’s natural resources.

Photo by Dennis Dow/Woodland Park Zoo.

Even as development lurches onward, Gretchen believes it is not inevitable that viable habitat and raptors should disappear from the landscape. What is inevitable is our connection to it. “It’s such big, open country,” she recalls. “You feel small, but that’s good. You see how really connected you are to all of life.” Building from this simple fact, we can shift our paradigm from merely energy consumers to proactive stewards of it, mindful of the species with which we share the planet’s resources. Green technology can design smart, and then smarter, ways to co-exist with wildlife. The keepers’ field work is an important contribution to helping wind power companies, policy makers and all who admire a blue—or a green—sky  make choices that keep raptors aloft.

Photo by Ryan Hawk/Woodland Park Zoo.

Editor's Note: This article is adapted from a story that first appeared in the Winter 2014 issue of MyZoo Magazine, Woodland Park Zoo's quarterly member magazine. Become a member today to begin your subscription.


Anonymous said…
Wind farms are ugly menacing sentinels - not silent and not harmless. Saw them in England as well, despoiling the landscape, just as they are doing so here. Such a tragedy that the bird population suffers from these blenders in the sky. How can they minimize these eyesores and the impact they inflict on nature? Green, indeed.