Hawks, Hawkwatchers and Wind Turbines

On Saturday I went up to Hawk Mountain Sanctuary’s Acopian Center for what was the 30th Kittatinny Roundtable hosted by the sanctuary’s senior biologist Laurie Goodrich. The roundtable gathers hawk counters from sites along the Kittatinny Ridge to talk about and analyze hawk counts from the previous migration seasons. In the afternoon Laurie usually has a speaker or two talk about some of their research. If you’re a hawkwatcher or a hawk counter or just a hawk dork like me, it’s a fun day.

This year two non-ridge hawkwatch sites from Delaware joined the fun. Hawkwatchers tend to be competitive about their preferred site and the hawks seen there. I’ve more than once known someone to count in horrible weather because they knew someone from another site would still be counting, and they didn’t want to miss seeing something. Sometimes one site will start counting earlier in the migration season in hopes it will give them more hawks than another site by the end of the season. And in cases where that other site does "beat" your own favorite site, there’s still plenty of ways to "win." You can always find one species where that other site didn’t see as many as your site. Or your site might have fewer counting hours but more hawks seen per hour. There’s always something. So the morning comparison of hawk counts is always fun.

In the afternoon, Laurie started off with Chris Farmer, who’s one of the main guys working on HMANA’s raptor population index. He’s a real statistics kind of guy but still manages to make most of what he says understandable to non-statistical folks. His talk was about the impact of wind farms on raptor and songbird migration. Raptors and other songbirds apparently can’t see or at least have difficulty seeing the blades of the wind turbines, which are often sited along ridgetops. Since that’s where birds also migrate, the potential impact on populations of birds as the number of wind turbines grows, is of critical concern to hawkwatchers. Chris is looking at where the turbines are located, plus the area of the blades’ sweeps plus the preferred height of migration by species to determine which species are likely to be most vulnerable to the blades. Birds that fly the highest will be less impacted than the ones who prefer lower flight paths. One thing I learned is that a 90 meter wind tower sweeps about 1.5 acres of air. Right now, it looks as though smaller raptors, such as the already declining kestrel and the sharp-shinned hawks, are among the most vulnerable.

I was especially interested in Chris’s discussion of the "non-lethal" impact of wind towers. Although birds can’t see the blades well, they can see the towers. Since many birds fly along ridges because the air around them produces updrafts that makes migration physically easier, avoiding the ridge because there’s a long line of towers atop them also creates problems. For example, a bird will use about 4 times the amount of energy during powered flight than during soaring. So if the migration path from Central America is lined with towers that the birds avoid, the trip will become even more fraught with difficulty than it is now. And how does that extra exhaustion impact breeding success, assuming of course, the birds survive a trip that’s 4 times more exhausting than it is today?

Proper siting of wind towers thus become crucial, as we are all suffering from issues with energy creation associated with oil right now. Siting towers away from ridge tops and known migration paths is vital. And to know precisely where some of the migration pathways are, studies through several migration seasons are needed and should be required, though they aren’t currently.
Some European countries also require that wind towers be turned off during days where migration is heaviest. That’s one way our daily hawkwatch count information could be a critical part of our future energy plans, though in the U.S. there’s currently nothing to require companies to turn off their wind towers. I’d like to think that kind of cooperation would be a possibility here, though, if only because a company would get a lot of bad press from one photo of our national symbol chopped in half by a wind turbine. It would be nice to think the wind companies would be environmentally aware enough to want to do that on their own, but I suspect national legislation would work a lot better.

The photo in today's post was taken in our meeting room in the Acopian Center. The man in the center is Maurice Broun, Hawk Mountain's first curator, who with his wife Irma, in the photo to the right, single-handedly stopped the sport shooting of hawks on the mountain, which led to statewide and then national legislation protecting all birds of prey. It's still possible to find spend brass .22 shells up near North Lookout. Hawk Mountain became the first sanctuary for birds of prey in 1934.