Actually, as soon as the snow blankets the ground, I go into owling mode, scanning tree tops and hydro poles for distinctive silhouettes. This heightened awareness comes from the knowledge that winter and early spring are the best times to spot one of the more unique members of the Order Strigiformes.
I’m referring to the Northern Hawk-owl (Surnia ulula). Their name alone suggests that they may be something a little different. They’re actually quite aptly-named. Unlike most of their fluffy, almost stocky cousins, these smallish owls are really quite streamlined, with relatively small heads, long tails and slightly more narrow wings. They’re also diurnal, hunting during the day, instead of exploiting the darkness like most other owls.
In the winter, these little stealth bombers come out into the open, perching high on the tops of spruce trees or old snags, sweeping the area with their eyes and ears, searching for scurrying rodents. Their sharp-eyed gaze can spot a vole bouncing over the snow up to 800 m away. When they find one, watching them pounce is a sight to behold. Most owls are relatively slow flyers, almost floating to a stop over their prey before they plunge to the ground for the final kill.
Hawk-owls are another matter. They usually don’t slow down. If the vole is on the surface of the snow, they don’t stop at all, snagging the morsel on the wing and swooping up to a perch to settle in with their kill. Their flight patterns are actually more like that of a Goshawk or a Cooper’s Hawk and that, coupled with their daytime habits, likely led to their common name.
These unusual birds are one of the least-studied of northern owls. Most of what we know about them comes from studies done in Scandinavian countries, where banders have worked diligently for decades to understand their owl populations. Here in North America, only about a dozen nests have been studied extensively. The fact is that they’re hard to work with. Although you can spot them with a fair bit of regularity during the winter, hawk-owls disappear into the bogs and old burns to breed during the spring and summer months, making them hard to find, right at that period in their natural history that we want most to understand.
What we do know is that they like tree cavities for nests, laying their eggs in old woodpecker holes or burnt-out snags. Like their northern neighbours, the Great Gray Owl and Boreal Owls, their reproductive success and thus their population numbers are likely tied to the cycling abundance of their rodent prey. Indeed, every now and then, large numbers of these birds will wing their way south out of their normal range in search of food, stirring southern birder populations into a frenzy. Still, we don’t really understand the mechanisms that drive them yet.
The scientist in me abhors this unknown and wants to work up a study and dive right into fray, teasing out patterns from the apparent chaos. However the writer in me likes that there are still mysteries left in our world.