A likely collapse of the small mammal population north of the border has sent large numbers of owls to northern Minnesota. That includes great gray owls, the largest owls in North America, as well as large numbers of boreal owls, which are among several species of small owls found in the U.S.
Great gray owls are seen much more frequently, both because of their size as well as the fact that they tend to be much more active during daylight than most owls. Northern Minnesota does have a year-round resident population of great gray owls, however during irruption years like this one, we can expect to see many more than usual.
Boreal owls, as with most small owls, are generally highly nocturnal, which means they’re not often seen by humans even if they’re around. While a small population is known to live in the Arrowhead, they’re considered rare outside of an irruption year.
Right now, the boreal owls are not only present in significant numbers, they’re showing up and hunting around rural residences during daylight hours given the extreme hunger they’re experiencing. We’ve had a boreal owl hanging around our house for more than a week—it’s the one pictured with this story. It’s remarkably unafraid of humans, you could probably pluck it right off its perch if you made the effort. It’s likely a combination of its lethargy from starvation and the fact that most of these little owls probably never see a human so have little natural fear.
I don’t know about the prospects of our recent visitor. I’ve yet to see it catch a mouse. Unfortunately, we’ve seen the same decline in the small mammal population here as they’re experiencing to our north. I suspect last winter’s lack of snow cover, which extended far to our north, was tough on the mice and voles and they don’t seem to have recovered quite yet. I know we haven’t trapped a mouse in our house in months, which is unusual.
While it’s fun to see these normally secretive owls, many of them likely won’t survive. Local ornithologist Steve Wilson, who has studied boreal owls for years, has documented the deaths of between 165 and 208 of them during four previous irruption years. Many, hopefully most, will find enough food to survive the winter. Of those that do, a few will likely stay in the area to breed this spring, as has happened in the wake of past irruptions, although most will likely return back to our north.
According to Wilson, in an irruption year like this one, we could see thousands, or even tens of thousands of boreal owls, head south in search of a food source. How many of them survive to return isn’t really known. If you find a dead owl, which will frequently show up near the foundation of rural residences, you can contact Wilson at 218-323-7633 and he’ll arrange to pick it up. It would be best to bag the carcass and record when and where it was found.
As their name suggests, these owls are residents of the northern forests. They are circumpolar, which means they are found in northern climes throughout the world, with Russia, especially Siberia, likely hosting the largest population. In Europe and Eurasia, they’re known as Tengmalm’s owl, named after a Swedish naturalist of the same name.
The female owls are substantially larger than the males, sometime twice as heavy as the male. This is common among raptors, but the difference in size between the male and female boreal owl is the most pronounced of any North American owl. Like most small owls, these are cavity nesters and those that survive will start thinking about breeding very soon. While normally silent, boreal owls start to vocalize about this time, a kind of monotonous twill, at night. They’ll continue to vocalize into April before getting down to the business of raising the next generation.
The good news is, their habitat is reasonably secure and their population across their wide range is believed to be stable.