This is a guest blog authored by Master's student Hannah Toutonghi, University of Minnesota-Duluth.
One of the first hawk owls to receive a GSM/GPS transmitter in Roseau, Minnesota. Photo credit: Steve Kolbe
Northern Hawk Owls (Surnia ulula) are one of the least-studied birds in North America due to their remote range in the northern boreal forests. Little is known about how far individuals travel, whether when leaving their natal grounds for the first time or after they have established a winter territory. They are enigmatic, feisty, and incredibly charismatic owls. Their unique behaviors and the lack of knowledge about the movements of hawk owls are just a few reasons why I chose to study this species.
Abbie Valine releasing a transmittered bird in Manitoba, Canada. Photo credit: Hannah Toutonghi
My research has focused on using novel telemetry methods to see if we can, for the first time, get a glimpse inside the life of individual hawk owls by monitoring their winter movements and microhabitat preferences in northern Minnesota and southern Manitoba. At first, it was a daunting task to try to find a transmitter that could collect detailed movement and activity information while surviving temperatures as low as -40 ℉ and keeping a charged battery all while remaining less than 3% of a hawk owl’s weight.
I made numerous calls to other researchers to inquire about their successes (and failures!) using transmitters and their manufacturer recommendations, as well as to inquire if they thought I could pull this off. With the help of Scott Weidensaul and Dave Brinker (founders of Project SNOWstorm) and cutting-edge ES-420 transmitters from Cellular Tracking Technologies (CTT), I found what I needed and was ready to commit all my waking hours to make this project a success. Even though there was some doubt about the available transmitter technology working on hawk owls, CTT staff was super helpful and this project would not have been possible without them.
Early mornings with a hawk owl that did not receive a transmitter in Manitoba, Canada. Photo credit: Hannah Toutonghi
Hawk owls are a low-density species that live in remote areas that are often difficult to access. Hundreds of hours of driving and scanning treetops went into locating these incredible owls, usually in unfavorable temperatures and conditions. Luckily, I was not alone and had the help of Frank Nicoletti and Jim Duncan who were both instrumental to finding and capturing hawk owls (as well as providing a wealth of experience, guidance, and moral support). With Frank, Jim, and numerous other volunteers, I was able to capture 19 total hawk owls (5 males and 14 females) and fit ten with transmitters.
Field Assistant Danny Erickson releasing a transmittered hawk owl in Manitoba, Canada. This is always the best part - watching the bird fly off unharmed and back to its normal habits! Video credit: Hannah Toutonghi
Map showing the winter home range clusters of all 10 hawk owls that received a transmitter. The next map will zoom in on a few of these home ranges!
This map shows NHOW 599 (female) who was caught in Manitoba mid-January 2022 and moved considerable distances all winter long! She covered many different habitat types, ranging from farmland to black spruce bogs.
This map shows NHOW 856 and 508 who were caught in Roseau, Minnesota, in early January 2022. The red points are the female (508) and the blue points are the male (856). The males range was over 3 times the size of the females!
Now we are getting data—and lots of it. During the 2022 field season, we saw many interesting patterns in the movements of the tagged Hawk Owls. Most stayed within a clearly defined winter territory during the winter months and did not leave this until early April. Some of these winter “home ranges” were much smaller than expected; one bird stayed within a one square kilometer patch of tamarack for the entire season! However, two birds that were caught near Roseau, Minnesota, have now flown over 500 miles north from their wintering location. Each travelled a considerable distance in a week’s time—unexpected (and amazing!) movement information for a species previously thought to be more non-migratory and nomadic in non-irruption years.
Three birds started moving north between March 18-21 2022, moving a considerable distance in only a couple weeks! NHOW 508 went the farthest, moving a total of ~1,200 km!
My next steps will be to conduct an in-depth analysis of the movement data from the ten tagged hawk owls by incorporating land cover, temperature, and snow depth data into a species distribution model to describe hawk owl winter habitat and home range preferences. Our results will provide novel data on hawk owl winter microhabitat use and highlight the importance of winter data for informing monitoring and land management plans. I hope this research will forward our knowledge of this species and contribute to helping this species thrive into the future.
The first hawk owl caught for this project was by David Alexander and Hannah Toutonghi. The bird did not receive a transmitter, but it was an exciting start to the project. Photo credit: Hannah Toutonghi
Thanks to: Wilson Ornithological Society, Raptor Research Foundation, Minnesota Ornithologists’ Union, Friends of Sax-Zim Bog, Discover Owls, Svingen Family Trust, Hawk Ridge Bird Observatory, Cellular Tracking Technologies, field season volunteers, and many fundraiser supporters. Without you, none of this groundbreaking research would be possible!
Follow along with the Northern Hawk Owl Project @nhow_project on Instagram.