2016 Winter Eagle Trapping

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2016 Winter Eagle Trapping

February 10, 2016

Raptor View Research Institute shares an update on their 2015-2016 winter eagle trapping efforts.

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In 2011, we outfitted two adult Golden Eagles with satellite transmitters to investigate their winter-habitat preferences and learn where they migrated during the breeding season. Since then, we have expanded our wintering eagle study to include all ages of Golden and Bald Eagles. While we still track adult Golden Eagles with satellite transmitters, we apply wing tags to younger Golden Eagles, and put color bands on Bald Eagles. We test each individual for exposure to lead, a contaminant apparently pervasive in eagles that winter in the Bitterroot Valley.

We’ve captured 15 eagles so far this winter—13 Golden Eagles and two Bald Eagles.

Trail cameras help us keep track of activity at our baits and identify eagles we’ve banded in previous seasons. So far this winter, cameras have captured visits from three of our wing tagged Golden Eagles.

All of the eagles captured this season had blood-lead levels higher than occur naturally (10 μg/dl). Sixty-seven of 74 eagles (90.5%) captured on the MPG Ranch since 2011 had elevated blood-lead levels, likely from consuming lead ammunition fragments.

In March of 2013, we saw a pair of Golden Eagles perform territorial flights near Whaley Draw. We believed these eagles may have been residents breeding in the Woodchuck Drainage and relocated one of our net launchers to target them. On March 8, 2013, we captured the large female, and outfitted her with a GPS transmitter. Unfortunately, she pulled her transmitter off in less than a week.

On December 18, 2015, we recaptured this female Golden Eagle at our Woodchuck trapping station, and decided to outfit her with another GPS unit. Her movements so far suggest that our initial guess may prove correct—she may be a resident of the Woodchuck drainage!

On December 30, 2015, we caught a Golden Eagle already wearing a band of unknown origin. After a flurry of phone calls and emails, we were able to contact the Alaska Department of Fish and Game biologist who banded the bird in its nest (below) near Nome, Alaska. Knowing its natal origin peaked our interest in this individual; with permission from the original bander, we equipped it with a GPS transmitter.

We captured this female Golden Eagle on January 9, 2016. While processing her, we noticed a large hole in the patagium of the right wing that had healed over. Though the eagle was in excellent health, the hole prevented us from wing-tagging her. We chose to outfit her with a GPS unit.

On February 17, 2013, we captured a third-year female Golden Eagle and gave her wing tags with the number 208. We encountered her for the second time on December 28, 2013, near our Woodchuck trapping station. The eagle was encountered a third time January 7, 2015, while feeding on a deer carcass (pictured below) near the Fred Burr trailhead in the Bitterroot Valley

On January 20, 2016, we recaptured 208 as she fed at our Woodchuck trapping station to test her blood-lead levels for a second time and inspect her wing tags after nearly three years of wear. Her wing tags were in excellent condition, and though her lead levels were higher than when originally captured, she was significantly heavier and well muscled. Now that she had reached adult status, we removed her wing tags and outfitted her with a GPS transmitter.

We captured this adult Red-tailed Hawk December 4, 2013. The bird showed the characteristics of being a Harlan’s Hawk, a northern-breeding variety of Red-tailed Hawk. After tracking her from her wintering grounds on the MPG Ranch up to her breeding grounds in Canada’s Yukon territory for two years, there was little more to learn from her movements, so we captured her as she fed on our bait in the North Center Pivot bait on January 18, and removed her transmitter. She was in fantastic condition, and had gained weight since her original capture. Before releasing her, we gave her a colored band, so we can identify her in the future.