Birders too, have avidly hunted for them with binoculars. GOLDEN OPPORTUNITY
It all began on Facebook. Through that internet
medium, I saw exciting photos of winter captures of Golden Eagles in the
mountains of West Virginia. I’d been a volunteer at the Allegheny Front
Migration Observatory at Dolly Sods in Grant County and had helped with the
hawk counts at Hanging Rock Migration Observatory in Monroe County, so I knew
the thrill of watching numbers of raptors course by, and of seeing songbirds
in the hand, briefly, before their release. I imagined it must be quite an
experience to do the same with a bird that is larger than a bobcat and that
has talons nearly as massive as a man’s fist. Golden Eagles, with their
golden tawny nape plumage, are less well-recognized, but certainly as majestic
as Bald Eagles, and have long been a species of mystery here. There are no
breeding records, although the birds were seen often enough in most seasons of
the year to warrant advice to cattle and sheep farmers to shoot them as
“varmints” in earlier times.
Birders too, have avidly hunted for them with binoculars.
So I was more than ready to attend a WV DNR lunchtime seminar, in March, on a study of seasonal populations of Golden Eagles in our state. There Trish Miller and Mike Lanzone, researchers from the Carnegie Museum of Natural History’s Powdermill Nature Reserve, shared a program on their current studies. Miller and Lanzone, with the cooperation of other groups including The National Aviary, the WV DNR, and the Pennsylvania Game Commission, want to determine the extent of wintering Golden Eagles on eastern mountain ridges. Unlike eagles in the American West, eastern Goldens have not been extensively studied. Indeed the work by the Powdermill teams leads them to believe that the eagles here may be a distinct subspecies, separate in several characteristics [wing measurement, leg size, behavior] from their western counterparts.
Miller and Lanzone’s presentation noted that eastern Golden Eagles breed in eastern Canada from the Gaspe Peninsula of Quebec to the northern reaches of Newfoundland and Labrador. Curiously there is often a telltale growth of orange lichens below their rocky aeries. The entire population is migratory. Their core of their wintering range virtually IS the area of the West Virginia mountains. The team’s research dispels notions about Golden Eagles primarily using expansive open areas here, as in the west. It was newly found that they winter in high-elevation forests and use the forest as well as small open spaces, in their winter roost and feeding locations.
There are multi-faceted conservation concerns for this bird. There is the expansion of human population that creates a number of problems, including habitat loss. There is also lead poisoning through ammunition-laden prey, persecution, and collision with human-made structures. The narrower focus of this study was to determine the numbers and travel routes of Golden Eagles in high ridges of Pennsylvania and West Virginia. “We want to know how they are using ridges,” Miller said. Also, “We want to know how weather and topography affect flight altitude and position along ridge tops so that we can understand the potential impacts of wind power development on migrants.”
Some eagles were captured and fitted with solar-powered satellite transmitters in Quebec and Pennsylvania. In West Virginia, bait for traps was road-killed deer. Surveyors were surprised at the number, usually 6-8 birds, that easily and quickly discovered bait stations. “This varied a lot with each site. The most surprising thing was when a single bird discovered a site within an hour of a carcass being dropped. At the most productive sites we counted a minimum of 15 individuals in a season (based on plumage differences),” Miller recalled.
The team developed new high frequency transmitters for this project, to determine fine scale movements and habitat use. With data resolution fine enough to detect the use of thermals by eagles, the study can show how birds respond to topography differently. The telemetry will enable researchers to see the response of birds to the turbines of wind energy installations. At wind facilities the risks may be the more obvious [turbine or blade collision] or less obvious [loss of habitat, loss of “lift” for migration, and “avoidance” behaviors. So, “…our goal is to model flight behavior in the ridge and valley province so that we can predict which individual turbines or which turbine facilities pose the greatest risk to migrants,” Miller noted. “We can use the model to make recommendations to remove, move, or shut down individual turbines. In some instances entire facilities may be poorly sited in which case we would recommend that the installation not be approved. In other cases we may find that the facility as a whole poses little risk to eagles.”
The team is hopeful that this study will be useful in planning and evaluating wind turbine facility sites. The home ranges (breeding grounds, not wintering locations) of eagles are being used to identify overlap with wind development. Because spatial pattern and land use appear to be consistent by the birds, and core use areas appear to be similar, predictions will be possible. Potentially even more helpful, models may be developed to identify strike probability in3D and can be used to modify siting!
Miller noted that their studies point to the distinct probability of the presence of hundreds of Golden Eagles in West Virginia each winter and that we, regionally have a high responsibility for ensuring the safety of them in that season and during migration. She spoke of her team’s positive interaction so far with “game and non-game folks,” and urged us to start thinking about “active” management.
I too was hopeful as I left the March meeting and began to take in this new information. Conservation-minded birders, like concerned folks everywhere, are scrambling to find out more about how our energy uses affect the environment that supports us. Studies such as this may help provide one part of solutions that can sustain us---and the birds.
---Cynthia D. Ellis
[for the web version…]
Pennsylvania nature writer Marcia Bonta has a wonderful piece on her website about the banding of a Golden Eagle by Miller and Lanzone on Bonta’s mountain property.
http://marciabonta.wordpress.com/category/birds/golden-eagles/