Owl irruptions happen every 4-5 years and we are definitely in one this year. There have been many sightings of owls from the Northern Boreal Forest all over the Midwest and the Northland this year. Interestingly enough there are four species of owl that periodically move south, and all of these birds are circumpolar birds found around the world in the Northern hemisphere. None of these birds are true migrators, but they do head south when food gets scarce in their normal habitat.
Snowy Owls are largely birds of the open tundra, and there have been a few sightings this year- but it appears that there were more that moved south last year than this year. These birds like to hunt in open territory, so aren’t necessarily looking for forested places when they move to the south, so they typically are seen in greater numbers to the west and east of us during irruption years.
The other three species of owls that irrupt are all birds of the Boreal Forest, in the last trees before the open tundra takes over, which is just a little south of the usual hangout for Snowy Owls. These include Hawk Owls, Boreal Owls, and Great Gray Owls. These are the birds that have been seen in greater numbers this year. All three species are primarily small rodent hunters, so it would make sense that many would head south at the same time when food becomes scarce. Thinking about all of them eating mostly the same thing had me asking how can they all inhabit the same area at the same time- that old ecological niche thing- seems like if they all occupy the same niche, they shouldn’t be able to coexist. This is a complicated question, so off to research some potential clues.
Seeking a little information to add to my bank, I found that though they have the same basic diet these owls have different hunting habits. Interestingly enough they hunt during different parts of the 24 hour cycle. Boreal Owls are typically nocturnal hunters and hunt primarily by sound, flying at night and turning their heads back and forth as they hunt listening for sound. Hawk Owls are diurnal hunters using daylight to find their prey- along with the ability to see prey up to half a mile away! These birds are also the least likely to head south in large numbers. The Great Gray Owls are more adaptable, hunting most often during early morning and late afternoon in the winter- though they are also known to hunt in daylight and at night at times. This is the crepuscular segment of the day (dusk). So between all three species of birds- someone is always hunting, no matter what time of the day you are watching.
Amongst these three birds, there are also three vastly different sizes. The Great Gray Owls are some of the largest owls in the world, with wingspans up to 60 inches and lengths of 24-33 inches. Hawk Owls are smaller, and fall in the medium sized owl group with a length from 14-16 inches. And the Boreal Owls are in the 8-12 inch long category, fairly small for owls.
In my quest for information I consulted another excellent resource, Frank Nicoletti, from Hawk Ridge Bird Observatory in Duluth. Frank has long studied these birds as well as captured and banded many of them, and through these years of experience has some interesting things to say about patterns in irruption years. He has observed this year that the influx of birds has come later in the winter than some irruption years, meaning that the small rodent population may have lasted through at least a portion of the winter before becoming limiting. Sometimes this can cause is a bit of a spill over into the next winter, which Frank calls an echo effect. This may mean that next winter could also be an irruption year, but we will have to wait and see what happens.
In the later part of the winter, many owls have been seen along the North Shore, following some of the typical patterns of birds travelling along the shoreline of Lake Superior rather than over open water. These birds are often easily seen perched along roadsides, and seem to be fairly tolerant of human observation, but a reminder to all of us, to keep our curiosity in check and no get too close. Remember, these birds are here because they are stressed and were starving in their normal habitat, so are often in a weakened state. Frank pointed out that we can help these birds out by giving them space, and doing simple things like shoveling the snow out from underneath bird feeders. These birds are after small rodents who typically raid the tailings from bird feeders at night. Lessening the amount of snow under your feeders makes it easier for these owls to harvest the mice and voles that are likely to look for stray seeds under the feeders. Can’t think of too many of us that have a problem with that- that many fewer to find their way into our houses and kitchens, and definitely for a good cause!
Frank also mentioned that he would like information on owl spottings in the area, where they are occurring and what time of day. If you are spotting owls in your daily movements, Frank would appreciate hearing about it. You can call him at 218-591-0174, or send him an email at firstname.lastname@example.org. So keep you eyes peeled for these late winter arrivals, add to the winter database of owl spotting, but remember to give them space when observing these fascinating visitors from the north!
These updates are made possible by a generous donation from David and Rosemary Good.