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fall migration monitoring & banding research

Our trapping teams were spread thin in 2007, with each location staffed by only two trappers and a few volunteers. RVRI Executive Director Rob Domenech, with apprentice trapper Tyler Veto (nice job, Tyler!) worked the Nora Ridge site, while returning biologists Tim Pitz and Vince Slabe teamed up to try their skills and test their stamina on the exceptionally windy and high (elevation 7500 feet) Grassy Mountain site. In the end, both teams were successful, with combined efforts resulting in an RVRI record-breaking total of 35 golden eagles banded in a single season!

Golden Eagle & Fall Raptor Migration Count from Nora Ridge

We were privileged to have our Nora Ridge count headed up by veteran raptor migration specialists Fred and Cathy Tilly, whose skills and overall expertise proved invaluable for this project. The numbers and species composition of migrants at Nora Ridge were very encouraging, and the 360-degree view from the north ridge observation point allowed Fred and Cathy to detect passing migrants from all directions.

Count Totals
In spite of a late mid-September start to the count and extended periods of overcast conditions, our count total was higher than expected. Observations were conducted from Sept. 15 through Oct. 29 for 39 days; six days were suspended due to impossible weather conditions. We totaled 2,672 raptor migrants in 253 hours of observation, comprised of 17 species, including turkey vultures. The golden eagle total came in at 1,616 (our highest to date) and comprised 60 percent of all observed migrants. Our all-time daily high count occurred on Oct. 13 when Fred and Cathy tallied 334 raptors, including 236 golden eagles!

Golden Eagles Separated by Age Class 

Other raptor species observed (species comprising less than 1 percent were listed)
Sharp-shinned hawk 250 (9 percent), Red-tailed hawk 195 (7 percent ), Cooper’s hawk 123 (4.6 percent ), Rough-legged hawk 112 (4.1 percent ), Bald Eagle 94 (3.5 percent ), Northern Goshawk 71 (2 percent ), Northern Harrier 35 (1.3 percent ), American Kestrel 31 (1.1 percent ), Osprey, Broad-winged Hawk, Swainson’s Hawk, Ferruginous Hawk, Merlin, Peregrine falcon, Prairie Falcon and Gyr Falcon 

Banding Summary, Nora Ridge
This season we moved our banding station south, roughly 1 mile down ridge. We strategically set up our two blinds, according to our flight observations from 2006and based on advice from mentor Steve Hoffman (executive director of Montana Audubon).

We trapped from Sept. 13 through Oct. 28 (weather permitting), for a total of 26 days. We banded a total of 57 raptors, including 18 golden eagles. (Please see tables below for complete totals.)

Golden Eagle and Fall Raptor Migration (Pilot Season) from Grassy Mountain

Pilot seasons can be very challenging to say the least. Due to the remoteness of Grassy Mountain, Tim and Vince were on their own nearly every day, coping with the extreme weather conditions of the Big Belt Mountains, as well as the daily challenges of running a banding station. However, with near daily moral and advisory support from Steve Hoffman, they pulled it off and, among many achievements this season, caught the two adult golden eagles that were instrumented with our satellite transmitters. Great job, guys!    

Observations from Grassy Mountain were conducted entirely from inside the trapping blinds, greatly limiting the ability to detect passing migrants. This was noted when they left the blinds to extract birds from nets. Future work will include full-time counters. Because of this we did NOT include a table of count totals. 

Count Totals
Observations and trapping were conducted from Sept. 10 through Oct. 24 (weather permitting). We observed a total of 1,049 raptor migrants in 176 hours of observation, comprised of 17 species, including turkey vultures. We counted 682 golden eagles, comprising 65 percent of total observed migrants.

Age-class breakdown of Golden Eagles 

* Count conducted exclusively from trapping blinds

Other raptor species observed (species comprising less than 1 percent were listed)
Sharp-shinned hawk 94 (9 percent), Red-tailed hawk 54 (5 percent), Cooper’s Hawk 38 (4 percent), rough-legged hawk 33 (3 percent ), bald eagle 16 (2 percent ), Northern Goshawk 19 (2 percent ), Northern Harrier 19 (2 percent ), American Kestrel 25 (2 percent ), Osprey, Broad-winged Hawk, Ferruginous Hawk, Merlin, Peregrine Falcon and Prairie Falcon. 

Banding Summary, Grassy Mountain
We banded a total of 30 raptors, including 13 Golden Eagles. Our focus was primarily on the Golden Eagles. We regard these numbers as good. For 2008 we plan to use samller lures and make up for our deficiency in numbers of smaller raptors. 

Fall (Sept. through Oct. 2001-2007) Capture Totals (Pdf)

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