Answering That Age Old Question

02 December 2022

"I wonder where that bird we just saw is going, and where it came from?" Whether you're a visitor to a migration site, or a crewmember, anyone that has spent time at a migration count site has pondered this question at some point or other.

It’s a question with value both for just pure curiosity's sake, but also from a conservation perspective. If we are to monitor and conserve populations of different species that use vast amounts of space over the year, knowing where those spaces are across an annual cycle is key. Put another way, knowing what populations we monitor by counting at a given site adds great value by putting a location to the declines or increases we document over time.

Many of our researchers at HWI use tracking technologies to study how different eagles, vultures, falcons, hawks, and owls use space. For larger species this technology allows for collection of years of near continuous data, but for medium and small raptors weight and power supply can still be limiting.

In 2020, HWI Research Biologist Jesse Watson and I started collaborating with several groups to track raptors migrating past sites in the HWI Migration Network. One of those efforts involves partnering with raptor biologists Tuk Jacobson and Kyle McCarty from Arizona’s Game and Fish Department. As part of this work we outfitted two female Northern Harriers caught on migration at the Goshute Mountains HawkWatch near the Nevada-Utah border with transmitters. We’ll refer to them by part of their transmitter #’s: 41670 and 12308. Both birds were what we call AHY or after hatch year, meaning that they’ve survived at least their first year of life—and making it past that point means a higher chance of surviving subsequent years for most wildlife.  Interestingly the team caught both birds on the same day, October 5, 2021. The type of tracking units we put on these two harriers store locations onboard, and then download data via cell phone networks. This means that when birds are in locations with no cell service there are long periods of silence, and researchers that use them can only wait and hope that the birds come back online at some point and share where they’ve been.

While some work tracking movements of Northern Harriers exists, notably that of Dr. Shannon Skalos in central California, the total number of individuals tracked is quite low for this understudied open-space species. Adding data from more birds and locations helps us better understand this species, and also answers that question…Where is that bird going, and where did it come from?

So, where did these two harriers that flew by the Goshute Mountains HawkWatch go? Both birds wintered in Mexico near Durango (41670) and Guadalajara (12308), but where did they come from before our crew briefly interrupted their southbound journey for the sake of science? Jesse, the crew, and I guessed locations in Idaho, Washington, or maybe British Columbia. It turns out we were all wrong. Both birds headed back to breeding/summering grounds in western (12308) and far northwestern (41670) Alaska—that’s just over 4,000 miles between wintering and summering locations and 8,000 plus miles round trip in a year! Incredible.


Both birds passed by the Goshutes much earlier this fall than last (nearly a month sooner for 41670). As of the writing of this blog, 41670 is back in the exact same area she spent last winter, and 12308 stopped transmitting just south of the New Mexico/Mexico border. While the journeys of these two birds are exciting, it will take more years of data and more birds with transmitters to paint a complete picture for Northern Harriers and other raptors.  We can’t wait to learn more from these birds and others, and to share their amazing journeys with you!



This blog was written by Dr. Dave Oleyar, HWI's Director Long-term Monitoring and Community Science.
You can learn more about Dave here.