This post was contributed by Hannah Toutonghi, a master’s degree student at the University of Minnesota Duluth and a 2021 WOS Research Grant recipient.
Northern Hawk Owl: even the name is mysterious. Hawk or Owl? Where does it fit in? Northern Hawk Owls are a “true” owl in the family Strigidae, but they have many traits typically associated with hawks. Hawk owls are active during the day, hunt largely by sight instead of sound, lack silent flight, and are shaped more like forest hawks than other owls. Adding to their captivating and mysterious ways is the fact that hawk owls are one of the least studied birds in North America due to their remote range in the northern boreal forests. However, during certain winters, large numbers of hawk owls abandon their northern territories and invade southern Canada and the northern U.S. 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. These 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.
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. This region is at the edge of the boreal forest and provides critical wintering habitat for hawk owls at the southern border of their range. Like that of many boreal forest denizens, the global range of hawk owls is predicted to shrink dramatically as northern forests recede in response to a warming climate, land management, and deforestation (Bateman et al. 2020, Langham et al. 2015, Virkkala et al. 2008). Successful conservation of hawk owls will require understanding hawk owl habitat use and range during their full annual cycle, including survival in changing winter conditions. Although many unknowns exist for this species, winter research on hawk owls is listed as a top priority (Nero 1995; Duncan and Duncan 2020).
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 -30 degrees F 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 technology from Cellular Tracking Technologies, I found what I needed and was ready to commit all my waking hours to make this project a success.
But the challenges associated with this project didn’t stop once I decided on which technology to use, secured enough funding (from sources including the Wilson Ornithological Society), and figured out how to juggle the project with classes and a teaching assistantship: I still had to find the owls! 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 hawk owls and fit ten with transmitters.
Now we are getting data—and lots of it. This past winter we have already seen 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.
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.
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, field season volunteers, and many fundraiser supporters! Without you, none of this groundbreaking research would be possible!