Northern saw-whet owls — the tiniest in eastern North America — have few rivals when it comes to cuteness.
A northern saw-whet owl is the tiniest, and arguably the cutest, found in Maine. They're migrating south for the winter. Credit: Courtesy of Bob Duchesne

Owls have been the subject of intrigue and myth for all of human history. Creatures of the dark. Silent killers. Omens. Their nocturnal habits and secretive behaviors have made them hard to study. Until now.

Northern saw-whet owls have few rivals when it comes to cuteness. They are the tiniest owls in eastern North America. Until recently, little was known about them. For a long time, we thought they were scarce. We’ve come to realize that they are quite common. They’re just good at hiding.

Most owls don’t migrate. Maine’s other two common species — barred and great-horned owls — rarely get far from where they hatched. Some owls of the frozen north may wander if weather or food scarcity force them south, but these atypical irruptions aren’t the same as typical migrations.

Northern saw-whet owls do migrate. They’re leaving right now, though they won’t go much farther than Virginia. They’ll return to Maine in March, starting courtship early.

Imagine how hard it would be to find and study a tiny, secretive, nocturnal bird that hides in the forest. They can be located in the spring by their territorial calls — a toot-toot-toot that supposedly sounds like a saw being sharpened on a whetstone. But even if you discovered the nest holes of a few owls, you wouldn’t have a valid sample size. Fortunately, owls are surprisingly simple to catch in migration. A bird in the hand is worth two in the bush.

That’s how I found myself at an owl banding site last week. Out of respect for private property and sensitivity for the owls, I can’t divulge the spot.

I will reveal only that it is somewhere on the coast. Saw-whet owls are reluctant to fly over water, and any owl coming south from northern Maine or the Canadian Maritimes will likely reach the ocean before reaching New Hampshire. Thus, most migrating owls get funneled along a coastal route. On a good night, biologists at this coastal site may catch 20 owls. On a great night, 40 or more. There are similar banding sites across the nation.

So what is it that we hope to learn?

We already know that most bird species are declining, some precipitously. We need to know if owls are in the same sad boat. By conducting long-term banding studies in the same spots, we can track trends. We’d also like to know if owls are successfully raising enough babies. We’d like to know if the northern forest is healthy enough to provide sufficient food.

Trained biologists can capture a bird in a mist net, take measurements and get the bird back in the air in just a few minutes. It’s amazing what just one saw-whet owl can tell you.

Females are larger than males in most raptor species and saw-whets conform to the norm. A female saw-whet owl weighs around 90 to 100 grams — think of a medium-sized tomato or four pickleballs. Males weigh about the same as three pickleballs. Biologists can determine gender just by weighing the bird.

Owls molt their flight feathers in different patterns. On a bird hatched this year, all the flight feathers will be new. On older birds, some feathers will be dark and worn, newer feathers will be bright and clean. The pattern varies by age, revealed by a quick visual inspection.

Furthermore, owl feathers have an unusual pigment called porphyrin that fluoresces pink under ultraviolet light. The pigment wears away over time. Under UV light, biologists can more accurately assess the age of the bird.

Saw-whet owl eyes are yellow, but the intensity of the yellow color varies by individual. The eyes of a well-nourished bird are a deeper yellow. That helps biologists estimate how many mice the forest has been providing for the owls, a sign of a healthy ecosystem.

Now take all that information gleaned from one bird, and multiply it by 20 per night, hundreds in a season and thousands across multiple sites. Saw-whet owls will tell us things non-migratory owls won’t. We know with statistical certainty, by comparing the number of older birds to younger, how many saw-whet babies the northern forest produced this year.

I say “we,” but in truth, it’s “they” — the biologists. I only had to stay up past my bedtime for one night. They are out there every night. Oh, to be young and underpaid again.

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Bob Duchesne, Good Birding

Bob Duchesne serves as vice president of Maine Audubon’s Penobscot Valley Chapter. He developed the Maine Birding Trail, with information at mainebirdingtrail.com. He can be reached at duchesne@midmaine.com.