Northern Saw-whet Owl

On the wild side—February, 2013

by Tina Mitchell

I first heard him on a frosty mid-January night in 2009; he called most nights until the middle of May.  Then he was gone.  No breeding success for him that year, I guess.  Winter 2010, not a sound; winter 2011, not a sound.  In February, 2012, though, I heard one again.  Over the next 3 weeks, I’d hear him every night—an incessant call of one-note “toots”— advertising for a mate.  This time, the caller would succeed and lead me into even more encounters with these little sprites—Northern Saw-whet Owls.

NSWOWhen most people think of owls, they probably picture the “giants” of this family—the Great Horned Owls, Barn Owls, or perhaps the Snowy Owl of Harry Potter fame.  But Colorado plays host to some diminutive owls too.  A winsome, and surprisingly ferocious predator—at least if you’re a deer mouse—the Northern Saw-whet Owl’s wide, almost heart-shaped head sits atop a chunky body and a stub of a tail, measuring about 8” tall in all.  Broad brown streaks cover its white chest and a white V stretches between the yellow eyes.  Should you ever see one, you might have to fight an urge to pop this munchkin into your shirt pocket.

These little owls inhabit pinyon/juniper woodland as well as some ponderosa pine woodlands.  If you wander through conifer stands during winter, you might spot this gnome, sitting very still, perched close to a tree trunk.  But don’t count on it, since their cryptic coloring allows them to blend into the nearby trunk beautifully.  Probably the easiest way to locate a saw-whet is to listen.  After dark early in the breeding season, a male gives a steady series of toots—1 or 2 toots per second—that may go on for hours with scarcely a break for a breath.

Breeding season begins very early for these sprites:  A male typically starts calling in February and eggs can be laid as early as March.  The female lays 4 – 6 eggs, about 2 days apart. Only the female incubates the eggs.  In fact, she remains on the nest with very few breaks from the time she lays the first egg until the youngest nestling is fully feathered and can keep itself warm (called “thermoregulation”)—roughly 18 days after hatching.  The male supplies food for her and the nestlings throughout this entire period.  The eggs hatch asynchronously, about 27 – 29 days later, in the order in which they were laid.  As a result, nestlings in the same brood can differ as much as 7 to 10 days in age and development.  They leave the nest after 4 or 5 weeks and remain together near the nest to be fed, mostly by the male, for another 4 weeks.

A saw-whet’s diet consists predominantly of small rodents, with a special preference for deer mice.  It also takes other species of mice, woodrats, chipmunks, young squirrels, and sometimes even smaller birds and large insects.  The saw-whet hunts at dusk or through the night, peering and listening from low perches and swooping down on prey.

The Northern Saw-whet Owl’s scientific name—Aegolius acadicus—comes from Greek:  aegolius, referring to a type of owl, and acadicus, referring to where the first saw-whet owl to be named was found (Acadia, Nova Scotia).   Similarly, its common name contains reference to the owl’s natural range in the U.S. (“northern”); “owl” likely comes from the Anglo-Saxon word ule, meaning “owl.”  Most interesting, though is the term “saw-whet.”  Early taxonomists thought that the male’s call sounded like the noise made when manually sharpening a saw on a whetstone.  Never having heard this sound, I’ll have to take their word for that.

So for the next few weeks, I’ll go outside with the dogs for one last time around 9:30 p.m. and I’ll listen.  Really hard.  Really, really hard.  Last winter’s calling male indeed found himself a lady friend and they set up housekeeping in one of our larger nestboxes.  She laid 4 eggs, 3 of which hatched into totally adorable nestlings.   And for a few weeks of nestbox monitoring during April and May, I got to spend a bit of up-close-and-personal time with this family.  You can read about my trials, tribulations, and anxieties of dealing with this new species; see lots of photos; hear a clip of this call; and learn even more about this wonderful creature of the night here.


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