by Karen Nichols
Although Northern Saw-whet owls are one of the most abundant forest raptors in North America, they are rarely seen due to their nocturnal and secretive nature.
Until recent decades, the diminutive owls were thought to be rare in many places and mostly non-migratory. Banding efforts over the past 30+ years are shedding new light on how common and migratory these owls are. Many Saw-whet owls disperse from their nesting areas in the fall and migrate.
This gives researchers an opportunity to capture and band thousands of owls across their range in autumn. Researchers, like Denver Holt and his colleagues at the Owl Research Institute (ORI) in Charlo, are capturing and banding these little owls to learn more about the owls’ movements and migration.
Holt has been studying Saw-whet owls for more than 40 years. This fall, they moved the Institute’s Saw-whet owl banding station to UM’s Flathead Lake Biological Station (FLBS). Many Flathead Audubon members were treated to close-up views of this enchanting little owl and the research.
Saw-whet owls are about the size of an American Robin but stouter. Adult owls have a round head, striking forward-facing golden eyes, and a light facial disk. Feathers are mottled brown and white, with a distinctive white ‘V’ between its eyes. The females are about 25 percent bigger than the males, as is common among raptors.
Few people will forget their first glimpse of a Northern Saw-whet Owl. They are captivating and simply adorable (unless you are a mouse or vole).
Fierce and efficient nocturnal predators, they capture small rodents with their feet and swallow them in chunks, starting with the head. They are well-adapted for nocturnal hunting with near-silent flight, keen night vision and asymmetrical ears that help them pinpoint prey.
The Saw-whet is not our smallest owl in western Montana; the Northern Pygmy and Flammulated Owls are a bit smaller.
They nest primarily in old woodpecker cavities. Snags, large dead or dying trees, provide not only nesting habitat for Saw-whet owls in Montana, but also for Boreal, Northern Pygmy, Western and Eastern Screech, Northern Hawk, Flammulated, Great Gray, Barred and Great Horned owls.
Saw-whets roost by day in dense conifers and thickets to rest and avoid predators like larger owls and hawks. They often show up in places like Lawrence Park and Owen Sowerwine. My first glimpse of a Saw-whet owl was in a crabapple tree outside of the old Hardee’s fast-food restaurant near Main and Idaho in Kalispell.
People are more likely to hear a Saw-whet than see one. The males sing their repetitive, too-too-too call, during the late winter and early spring breeding season, at a rate of about two-three toots per second.
To the modern ear, this sounds like the warning beep of a truck backing up. However, historically, the sound reminded people of a saw being sharpened with a file, hence the species’ common name. The owls make up to 10 different vocalizations, from squeaks to high-pitched alarm shrieks to barks and guttural sounds.
Birders in search of these owls often find them near eye-level in dense thickets. To find such a roost, look for clues such as pellets and whitewash at the base of the trees. Also, keep an ear out for agitated small birds like chickadees and nuthatches. Even though Saw-whet owls rarely prey on small birds (unlike the similar Northern Pygmy Owls), the small birds tend to mob owls.
The female does most of the nesting, with the male bringing food for her and the newly hatched young. The eggs are laid one to two days apart. When the youngest nestling is about 18 days old, the female often leaves the nest to roost elsewhere. The male takes over nesting and feeding the young. (It is not known if the female brings food for the male and young or simply leaves.)
The nest is kept clean while female is brooding the young; all the pellets and feces are removed. Biologists have noticed that when the male takes over nesting, pellets, feces, and rotting excess prey build up in a layer several centimeters deep.
The ORI site at the FLBS is one of more than 100 Saw-whet owl banding sites across the U.S. and Canada. ORI researchers set up mist nets for 40 nights this fall and caught and banded 180 birds. The researchers found that 73 percent of the owls captured were females, while 9 percent were males and 18 percent unknown, suggesting that females may be more migratory than males. Also, 78 percent were birds that had hatched that year.
While many banded owls are never caught again, some recaptured owls yield big surprises. One bird banded on Montana’s Rocky Mountain Front in 2003 was recaptured two years later near Boston, Mass.
Studying Northern Saw-whet Owls is challenging because they are nocturnal, secretive, and have irregular seasonal migrations. While scientists like those at the ORI are answering many questions about these fascinating birds, many mysteries remain.
Sources: The Owl Research Institute; The Cornell Lab of Ornithology; Birds of Montana by Jeffrey Marks, Paul Hendricks and Daniel Casey; and What an Owl Knows by Jennifer Ackerman.