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Night Owls

Article By 
Ron Wilson

While the Northern saw-whet is an infrequent visitor to North Dakota, the owl is easily discernible because of its small size and yellow eyes.

While there may be a breeding record or two in North Dakota, the Northern saw-whet owl is mainly a transitory whisper passing through on seasonal migrations to who knows where.

Last fall, researchers with the Rocky Mountain Bird Observatory in South Dakota gathered in the South Unit of North Dakota's Theodore Roosevelt National Park in hopes of capturing and banding saw-whet owls.

Using mist nets and game callers heralding the owl's territorial call, researchers working under the cover of darkness caught, banded and released 106 migrating saw-whets in 31 nights from October 1 through November 7.

It turns out that the Little Missouri River area in the badlands is a major migration corridor for saw-whets. Researchers believe the dense vegetation along the river's winding route is attractive to the birds that favor this kind of habitat for roosting and replenishing during their travels.

"The number of birds we catch in North Dakota is two to three times that of what we catch in South Dakota," said Nancy Drilling, RMBO biologist.

 

The Northern saw-whet owl gets its name from one of its calls that birders say sounds like a saw blade being sharpened by a file.

Northern saw-whet owls are almost entirely nocturnal. Under the cover of darkness, the owl becomes a hunter, preying on small rodents.

What immediately strikes you about the saw-whet is its size. It's a diminutive bird, as far as owls go, measuring about 7 inches or so. Drilling said saw-whets are small enough that researchers put them in empty frozen orange juice containers to weigh them after capture.

"Male saw-whets are smaller than females," she said. "These birds are basically just a fist full."

Another interesting thing about the small, yellow-eyed owls is their nonchalance. Saw-whet owls come across as incredibly tame, and are easily approached in the wilds.

"If you find one sitting in a tree, you can walk right up to it," Drilling said. "Their defense mechanism is to freeze and hope that you don't see them. They are probably frightened, but come across as docile."

 

All saw-whet owls captured in western North Dakota last fall were fitted with leg bands.

Saw-whets feed on insects, but their main food source, Drilling said, is mice. While other bigger predators will eat a mouse in one gulp and move on in search of another, the saw-whet eats just part of its catch, caching the remainder for later.

After saw-whet owls are rescued from mist nets by researchers, they are banded, aged and checked to see what kind of shape they're in.

"To check their health condition, we look at the body fat on the owls," Drilling said. "We do this by blowing on the feathers to see how much fat is underneath."

Eight owls captured in Theodore Roosevelt National Park last fall were already banded. Three were originally banded in Saskatchewan and one in Duluth, Minnesota. Another bird was banded in 2010 on the shores of Lake Ontario. That's about 1,300 miles from southwestern North Dakota as the owl flies.

In her 2013 report, Drilling wrote: "Biologists had no idea that owls in the east and east-central parts of the continent would travel so far west. In addition, Saskatchewan banders assumed that some of their owls migrated south, but until this year had no confirmation of that hunch."

Where saw-whet owls are headed when they migrate through North Dakota's badlands in fall is unknown.

"That's the big mystery," Drilling said. "That's one of the reasons we are doing this research."

 

Helpful Research

The North Dakota Game and Fish Department's involvement in the Northern saw-whet owl banding effort in the western part of the state was to provide a scientific collection permit to researchers.

Yet, interest in what researchers from the Rocky Mountain Bird Observatory in South Dakota are doing in the badlands doesn't end with a signature on the permit.

"Very little, if any, research has been done on Northern saw-whet owls in North Dakota," said Sandy Johnson, Department conservation biologist. "Any information we can learn from this study is helpful in how we manage these and other nongame animals that go mostly unnoticed."

While it's likely saw-whet owls depend on North Dakota simply as a place to rest and replenish during their migration, that's something wildlife managers, tasked with the duty of managing many game or nongame species, need to know.

"No matter how big or small, breeding birds or those just passing through, we must look out for all of them, even if they see us, but we don't see them," Johnson said.