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Raptor takes researcher north to Alaska to look at a special winter visitor

Posted by Jim Watson, Wildlife Research Scientist, Washington Dept. of Fish and Wildlife

Jim Watson is a friend of the zoo and works with our Living Northwest Conservation Program's Raptor Ecology of the Shrub-Steppe Project. Jim has partnered with us for years and we are excited to share his most recent adventures in raptor research:

When Washington Department of Fish and Wildlife and the Woodland Park zoo started our cooperative raptor studies in the shrub-steppe of the Pacific Northwest 20 years ago we probably didn’t envision we were embarking on such a long-term journey. This productive relationship has delved into important projects including migration studies of ferruginous hawks and golden eagles, and how human activities like construction of wind turbines and lead contamination in prey are affecting these iconic raptors. We took advantage of a recent opportunity to look in a little different direction for our cooperative studies within the shrub-steppe raptor community.

Jim and captured rough-legged hawk wintering in Idaho 40 years ago. Photo by Ranae Watson.

Rough-legged hawks

Forty-years ago very little was known about a winter visitor to western North America. This raptor, the rough-legged hawk, was under-studied in winter and its breeding habits in the Arctic were also largely unknown. The hawk was known for its proclivity to hover-hunt, and seen frequently perching in remote areas along fenceposts and powerlines in snow-covered habitats. I was fortunate enough to investigate rough-legged hawk winter ecology for my Master’s degree in the early 1980s. With the help of my wife, Ranae, we tracked several hawks with VHF (ground) telemetry from shrub-steppe habitats in southeast Idaho into Montana, but was left wondering: where do these hawks nest? How far do they migrate? Do they return to the same nesting area each year?

A lot has changed in the last 40 years. Most importantly, climate change has evolved from a topic of discussion to a reality. Arctic-dwelling species, like the rough-legged hawk and gyrfalcon, may be the most impacted from climate change. As one example, overall warmer temperatures allow the permafrost to thaw and then when it refreezes it makes a layer of ice that may be impenetrable and fatal to small mammals like lemmings that are critical food for arctic raptors. Though rough-legged hawks are considered to be common, but for how long?

Lemming killed by a jaeger. Photo by Jim Watson.
Another change in the past 40 years has been the evolution of light-weight satellite transmitters that allow remote monitoring of birds using the accuracy of GPS technology. We began radio-tagging rough-legged hawks about 15 years ago in Washington to investigate their movements on shrub-steppe habitats where wind turbines were being constructed. As it happened, other researchers were also radio-tagging rough-legs in other states and one researcher, Jeff Kidd, coordinated collaboration among researchers to pool our migration data to be able to define northerly range-wide migration patterns for this species. However, there was still little information on breeding origins and ecology of these hawks because they had not been captured and tracked from breeding ranges.

Alaska to Washington

In early July, 2019, I accompanied 4 researchers to Nome, Alaska, to capture rough-legged hawks on their breeding ranges and radio-tag them to study their local movements and migration. Rough-legged hawks nests on cliffs on the Seward Peninsula, among gyrfalcons, golden eagles, and peregrine falcons. Rough-legs nest sporadically in the tundra, reflecting changing prey conditions, and 2019 was a good year for nesting. 

Expansive arctic habitat provides nesting habitats for many raptors and ravens. Photo by Jim Watson.
Unfortunately, the first 5 days of in the field were met with unseasonal weather – high winds and rain – that were not conductive to capturing hawks. We spent that time scouting out nests, which, to my surprise, was not simply an easy walk across the flat tundra. Nests that are on the level tundra (including some ground nests) require taking calculated steps among the tussock (grass clumps) and those on distant hills involve vigilance to avoid grizzly bears that were quite common and hard to see among willow thickets. Musk oxen were also common, but didn’t create the same sense of caution.   Mosquitoes were not measured in tens, but hundreds (thousands??), but quickly became part of the accepted routine and more than a few were swallowed or inhaled during regular activities.

Vigilance for grizzly bears is important when hiking in the tundra. Photo by Jim Watson.

Musk oxen herds are not uncommon on the Seward Peninsula and they feed on mosses and lichens. Photo by Jim Watson.
Fortunately, we were able to resume capture activities after a couple sunny days that reached into the mid-80s. We found several hawk nests that had failed during the bad weather, but were fortunate to capture 2 of 8 or so hawks of nest territories that were still active. We set out to capture hawks at 2:00 AM, when the winds were calm, temperatures cool, and the sun never sets. 

Rough-legged hawks nest may fail after heavy spring rains and wind. Photo by Jim Watson. 

Field work can continue all night in the land of the midnight sun (2:00 AM). Photo by Jim Watson.
We found that some of our traditional capture methods, that use prey to attract hawks, were ineffective in the arctic because prey was particularly abundant in 2019. The weather didn’t “dampen” our enthusiasm for capturing and radio-tagging this special raptor, which for me came 40 years after I first captured them on winter ranges in Idaho! The chicks, that watched the entire operation from the nests, were less impressed. After measuring and banding the hawks, we released them back on their nesting territories where we await their return to the lower 48 beginning in October.

Jim and captured rough-legged nesting in the Arctic 2019. Photo by Neil Paprocki.

Nestling rough-legged hawks. Photo by Jim Watson.
What's ahead?

The future plan for is for the research team to complete breeding telemetry studies in the next year or two that will result in a comprehensive pattern of hawk use when combined with winter migration. From a Washington perspective, our interest is to see whether there is a consistent origin of hawks that winter in Washington from between the North Slope south to the Aleutian Islands, and if so, what might be the future impacts to these nesting populations from changing taking place in Alaska? 

Conversely, this information will reveal what breeding populations of rough-legs we may be impacting from human activities on winter ranges like agricultural conversion, wind turbines, and mortality from shooting and vehicle collision. The study will also provide data for several topics including rates, whether there is differential use of wintering ranges by male and female hawks, and the importance of different areas, including Washington, to the wintering hawk population in western North America.

Rough-legged hawk hovering near wind-turbine in eastern Washington. Photo by Jim Watson.

What do we hope to learn?

Our participation in the study will allow us to tap into the comprehensive data set to return to our investigation of winter range use, winter range fidelity, and why and how often these hawks use stopover areas that include human threats like wind turbines.

To learn more about protecting the raptors of Washington's Columbia Basin, check out the Living Northwest, Raptor Ecology of the Shrub-Steppe program. Special thanks to Jim and the Washington Department of Fish and Wildlife for sharing this incredible up close look at conservation in action!