June 28, 2018

Boreal owls perform by daylight

Posted by larryohanlon

By Ned Rozell

Just beneath the owl box, hung 20 feet up the stem of a balsam poplar, the backyard barbeque continued late into the evening. Despite the thwap of badminton birdies and the chirp of human voices, the boreal owl had work to do.

With a vole in its talons, the hand-sized bird perched on a branch outside a wooden box nailed to the tree. After a quick scan of the activity below, the owl bent and grabbed the vole with its beak. It fluttered up, hovered, and slam-dunked the vole through the hole. 

The owl then disappeared into the shadows of the spruce forest. Scratching noises came from the nest box as the adult female within tore apart the vole into pieces her hatchlings could swallow. 

A boreal owl chick that hatched recently in Fairbanks. Photo by Ned Rozell

Over much of their range, boreal owls operate in the dark every night. They live south to Colorado and in a forested belt around the northern part of the globe. 

People know boreal owls in Europe and Russia as the Tengmalm’s owl. Here in Alaska, biologist Tim Craig found boreal owls in his nest boxes north of Coldfoot along the Dalton Highway, almost to where there are no trees. But — fun fact — he found none in his string of boxes just south of Coldfoot on the highway.

In the far north, where there currently is no night, nocturnal animals like flying squirrels and owls need to go about their business in daylight.

“None of these animals out there are sacked out for eight hours like we are,” said UAF ecologist Knut Kielland, who studies lynx and hares, among other creatures.

An adult boreal owl in late winter. Photo by Ned Rozell

Mad increases in daylight cue chemical changes in the brain that enable animals to ditch their circadian rhythms, Kielland said. Moose, for example, can strip willows for two hours then lie down for a few hours, repeating that cycle all day and all night. Though owls, bats and flying squirrels are more active in the dimmest part of the day, they are not living the life they are in Washington state.

As the Fairbanks backyard party continued past midnight, the male owl returned. He carried another vole. During studies in the early 2000s, biologist Jack Whitman found that boreal owls outside McGrath and Fairbanks fed mostly red-backed voles to their nestlings, sometimes switching to meadow voles when they were available and grasses and sedges were short. Owls fed their young other birds, mammals and insects too, but voles were by far the number one prey of Aegolius funereus.

About that Latin name: the genus name Aegolius is a type of screech owl thought to be a bird of ill omen. Funereus means dark, deathlike, funereal. It is also the name of a death metal band from New Jersey. Seems a bit heavy for one of the friendlier-looking owls out there. 

The boreal owl’s roundish face is disk-shaped, like a radar antenna bouncing the slightest rustle of twigs to the owl’s ears. The boreal owl is one of few creatures with a lopsided skull — one ear is lower than the other. This asymmetrical head further helps a boreal owl pinpoint the skitter of a vole through leaves.

A boreal owl resting on a spruce branch. Photo by Ned Rozell

The male owl above the party seemed to be on a regular commute from his vole hunting grounds to the owl box. For all we knew, he might be delivering to two boxes. Near McGrath, Jack Whitman found the rear half of one snowshoe hare in one box and the matching front half in another, just 1,200 feet away.

“I suspect one male (was) maintaining two females with broods at these particular sites,” he wrote.

The humans walked away from the party after the sun set, but before it rose again at 3 a.m. I returned a few days later and saw the dusky head of a boreal owl chick peering out of the box. Soon, it will take its first leap into the world, beginning a life of three or four bright summers. If that chick is a male, (females often leave the area), the owl will probably haunt these same spruce on the darkest days of December.

Ned Rozell is a science writer for the University of Alaska Fairbanks‘ Geophysical Institute. Since the late 1970s, the Geophysical Institute has provided this column free in cooperation with the UAF research community. More of Ned’s columns can be found hereFollow Ned Rozell on Twitter at @NedRozell  and on Instagram at @neddyrozell