Montana's raptors counted yearly for population data
A magpie pulls at the tail feathers of an immature bald eagle in the Mission Valley. The valley is a great place to look for raptors — particularly in the winter.
If you can hike two miles and count birds, you could be a volunteer for a cooperative migration survey effort in the Jewel Basin.
For 10 years, ornithologist Dan Casey has been conducting surveys throughout the fall to establish local bird population and migration counts. A former resident of Somers, Casey started the project after a preliminary count in September 2007 yielded 152 birds in four hours.
Casey noted that the Jewel Basin is unique in that it hosts a high number of accipiters – small, forest-dwelling birds of prey. The most common bird observed during the migration survey is the sharp-shinned hawk, the smallest hawk in the United States at about the size of a jay. Other dominant bird species are Cooper’s hawks, golden eagles, and red-tailed hawks.
Casey used to work for Montana Fish, Wildlife, and Parks in Kalispell, then the American Bird Conservancy. He now works for Ducks Unlimited in Billings but continues to participate in the Jewel Basin survey.
“This is one site among many sites, and by putting our data into a larger dataset, you can look at continental trends,” Casey said.
And those trends don’t spell good news for golden eagles, which have declined over the past 10 years in the Jewel Basin. Red-tailed hawks and Cooper’s hawks have increased.
It’s the golden eagles that take the forefront in the Big Belt Mountains, though.
In the Big Belts, Golden Eagle Migration Survey volunteers sit at 8,100 feet at Duck Creek Pass in the Big Belt Mountains from September till mid-November.
The Big Belts start near Great Falls and run south to Helena, and represent an important flyway for golden eagles. By using the mountain updrafts, the raptors make their migration much more calorically efficient.
The survey is a collaborative, science-based effort to study the fall migration of raptors and their population status. The goal is to track the population for at least a decade to establish a threshold for population and ecosystem sustainability.
During the first census in fall 2015, a remarkable 4,318 migrating raptors of 17 species – including 2,630 golden eagles – were counted.
In 2016, more organizations got involved, including Montana Audubon, Last Chance Audubon, the U.S. Forest Service, and Montana Fish, Wildlife, and Parks.
“Golden eagles are of particular interest to the conservation community,” project founder Steve Hoffman noted.
The raptors are a barometer of ecosystem change. They’re susceptible to habitat loss but also other human impacts like electrocution, lead poisoning, and collision with wind turbines.
They’re also popular and well-loved.
“Golden eagles are one of the most charismatic birds out there,” Hoffman explained.
Their flight behavior is captivating, whether they’re gliding on drafts or plunging to hunt, and they may mate for life, according to the Audubon Society website. Missoula’s Raptor View Research Institution has tracked the birds using radio transmitters and reports that they come from as far north as Alaska and travel south to Texas, Mexico, and Arkansas.
Hoffman, a bird conservation ecologist of 40 years, started his raptor research in 1991 in the Bridger Mountains near Bozeman. Since 1991, he reported, golden eagle numbers have dropped 35 to 40 percent – a significant loss.
When Hoffman started exploratory counts in the Big Belts in 2014, he counted more than double the number of golden eagles he’d seen in the Bridgers. In the last few years, the decline of golden eagles has arrested slightly, but there are still substantially fewer than there once were.
Numbers of other raptor species were comparable between the Big Belts and the Bridgers, but other survey sites in Montana are dominated by higher numbers of different raptors, like kestrels or hawks – indicating that varied Montana habitats could be home to different dominant raptor species.
“We can eventually answer the question, ‘How are the other raptors doing over time?’” Hoffman explained. “Each species has its own habitat and there’s different threats to those habitats.”
Flathead residents interested in the Jewel Basin survey can contact Flathead National Forest, Flathead Audubon, or B.J. Worth at Wings in Nature, 249-3535. Casey can be reached at 270-5941 and Hoffman at 461-5714.
“We always encourage people to lend their eyes to the effort. It’s two miles so it’s a bit of a hike, but it’s worth the effort,” Casey said.