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Blane Klemek: Watch out for those Northern flying squirrels

Sometimes I fill my bird feeders at night. Not because I expect any nighttime avian visitors to descend from their nocturnal roosts for a late night snack, but because yours truly sometimes is pressed for time in the early morning hours before he departs for work. Indeed, filling the feeders at night ensures that the wild birds will have “full plates” even if I’m running late. And at this writing, only moments before, was one such night.

I had just carried a couple bags of groceries to the front steps and shoveled a light dusting of drifted snow off of my sidewalk when I decided that now would be a good time to fill the bird feeders. So, with my headlamp lighting the way, I walked to the shed where I store my black oil sunflower seeds, scooped a pitcher full of seed from the aluminum garbage can, and walked to the backyard to fill my two feeders — one squirrel proof fly-through feeder mounted on a post, and the other “non-squirrel proof” hanging feeder.

As I approached the feeder that hangs by a lightweight chain attached to a limb of a birch tree, I was about to grasp the feeder to unscrew its lid when I was surprised by the sudden and silent motion of what seemed almost bird-like in both appearance and movement as — whatever it was — leapt or “flew” from the feeder to the nearby birch tree.

I followed the blur with a quick turn of my head, which of course cast the bright light of my headlamp in the same direction. Not seeing anything on the bright white bark of the paper birch tree, I quickly stepped to the opposite side of the tree and peered up its trunk in hopes of catching sight of what I was pretty sure I had just observed. Sure enough, about 15 feet high in the tree, I caught a glimpse of a very good reason to keep one’s bird feeders filled even at night — a flying squirrel!     

Two species of flying squirrels inhabit Minnesota: one, like my furry little friend filling his belly with sunflower seeds, is the northern flying squirrel (Glaucomys sabrinus). The other species is the southern flying squirrel (Glaucomys volans). Both mammals are rodents and are members of the squirrel family, Sciuridae. It is the northern flying squirrel that populates our forests here in the Northland.

Northern flying squirrels have the most extensive range in Minnesota and North America. They occur throughout central and northern Minnesota in a variety of forest types. The North American range of southern flying squirrels is mostly east of the Mississippi River, which includes central and southeastern Minnesota. Both species prefer habitats of mature, broad-leaved forests.

Northern flying squirrels are larger than their southern relatives — about a foot versus 9 inches long. Both species are about the size of chipmunks. The color of their fur coats is similar for both squirrels, ranging from brownish to brownish gray. Their belly fur is whitish.

The tails of flying squirrels, a distinguishing feature, are long, flat and fluffy. Such tails act as rudders as they glide through the air. Their eyes are very large and ringed with black fur. But the flying squirrels’ most unique feature is the folds of skin between their legs. This furred membrane, called a patagium, stretches between the front and back limbs and is attached to the ankles and wrists.

Flying squirrels are especially active at night, but can also be observed at dusk and dawn. They feed on a variety of seeds, grains, fruits, berries, buds, and nuts. Their diet also includes fungi, mushrooms, insects, bird eggs, and even young birds and carrion. The inquisitive and docile acting squirrels are common nighttime visitors to backyard birdfeeders. Most people don’t mind watching bands of flying squirrels raiding their feeders in the dark of night.

Contrary to some beliefs, flying squirrels really don’t fly — they glide. The whole sequence, from launch to landing, is really nothing more than a controlled freefall. By launching themselves from the upper parts of trees and other structures, flying squirrels glide through the air to reach the lower parts of nearby targets.

This amazing descent is accomplished by extending their limbs to expose the patagium stretched between their feet and by holding their tail straight behind them. Flying squirrels are capable of maneuvering and steering their bodies in order to land where they want to. Resembling Aladdin’s flying magic carpet, a flying squirrel’s glide can extend 100 feet or more.

Nests are usually constructed inside naturally occurring tree cavities and woodpecker holes. But, as I’ve learned over the years, bird houses, and even wood duck houses, are favorite nest sites too. During the winter, several flying squirrels will often den together to stay warm. Litters of up to seven, usually two to four, pups or kits are born blind and hairless in the spring.  

For sure, if you feed birds and are fortunate to live where flying squirrels inhabit, which is probably the case whether you know it or not, keep a watchful eye on your birdfeeders at night. If you discover that flying squirrels are present, try arranging outdoor lighting directed at your feeders in order to better observe these special species of squirrels. Or feed your birds at nighttime with a headlamp strapped to your head and, believe me, you might be surprised to see a flying squirrel as you get out and enjoy the great outdoors.

BLANE KLEMEK is a Minnesota DNR wildlife manager. He can be reached at bklemek@