Northern Saw-whet Owl - Aegolius acadicus
Calls - Aegolius acadicus
Introduction: European explorers first discovered this Owl in a North American colony called Acadia (now Nova Scotia). The Latinised word "acadius" refers to this territory. The common name "Saw-whet" comes from these Owls unique calls described below. The Saw-whet Owl is also called Acadian Owl, blind Owl, Kirkland's Owl, the saw-filer, the sawyer, sparrow Owl, white-fronted Owl, Farmland Owl, Little Nightbird, Queen Charlotte Owl, and even the Whet-saw Owl.
Common Misspellings: sawwhet owl, sawhet owl.
[For help with terms used in the description, see parts of an owl. For general characteristics common to most owl species, see owl physiology.]
Description: The Northern Saw-whet Owl is a very small, short-bodied, Owl with a relatively short tail. The overly large head has no ear tufts and may appear distorted due to an asymmetrical skull. They look small when perched and tend to shuffle their feet, but in flight appear larger because of their broad wings.
The facial disk has brownish and whitish radials around the edge, which fade to a whitish area around the eyes. There is also a dark area from the base of the bill to the bottom inside edge of each eye. The rest of the head is brownish to grey-brown and densely covered with white streaks, especially on the forehead. The eyes are large and bright yellow-orange. The bill is black.
Plumage is quite fluffy and brownish or reddish brown overall streaked with white underneath and spotted on the back. Flight feathers are spotted white. The legs and feet are light buff and heavily feathered. The toes are lightly feathered and the claws are dark horn with blackish tips.
Size: Length 17-21.9cm (6.7-8.6"). Wingspan 45.9-56.3cm (18.1-22.2").
Weight 75-110g (2.6-3.9oz). Females are slightly larger than males.
Habits: Northern Saw-whet Owls are strictly Nocturnal, with activity beginning at late dusk. During the day, they depend on plumage for camouflage when roosting in foliage, usually close to the ground. When threatened, a Saw-whet Owl will elongate its body in order to appear like a tree branch or bump, often bringing one wing around to the front of the body.
Flight is rapid, woodpecker-like, laboured, and undulating.
Voice: The Northern Saw-whet Owl vocalises during the breeding season only (usually between March and May). They are silent at other times of the year. The primary courtship call is a monotonous, whistled "hoop", emitted at about 1.5 notes per second which may last for several hours without a break. Territorial calls are series of short clear notes. The Saw-whet Owl's name comes from the "skiew" call that is made when alarmed. This sound has a resemblance to the whetting of a saw. When the male flies to the nest with food it gives a rapid staccato burst of toots, and the female responds with a soft "swEE".
Hunting & Food: These Owls hunt mainly at dusk and dawn and most often use the "sit and wait" tactic to drop down onto prey on the ground from low hunting perches. They will also range through wooded areas and hunt in heavy shrub cover. When prey is plentiful, a Saw-whet Owl will kill as many as 6 mice in rapid succession, without consuming any of them. The excess food is cached in safe places and, in winter, is thawed out later by "brooding" the frozen carcass. When food is plentiful, it is common for only the head of each prey to be eaten.
Northern Saw-whet Owls feed almost entirely on small mammals, Deer mice being the primary prey, followed by shrews and voles. Other mammals include squirrels, moles, bats, flying squirrels, and house mice. Small birds are sometimes taken and include swallows, sparrows, chickadees, and kinglets. Larger birds such as Northern Cardinal and Rock Dove can be killed by one of these small Owls. Frogs and insects are also part of their diet.
Pellets are very small and dark grey, about 1.9cm (0.75") by 1.3cm (0.5") and are ejected with great difficulty, usually with a great deal of twisting of the body and head.
Breeding: Because of their nomadic nature it is unlikely that pair bonds are permanent or that birds often return to the same nest site. Males sing their territorial song mainly in late-March and April. After a female has been attracted to a male by his song, he will fly in circles above her while calling, or he will take her directly to the nest site he has located (again, while calling). The male then lands near her and begins a complex series of bobbing and shuffling as he inches towards her. Often, the male has a mouse in its bill and offers it to the female.
Northern Saw-whet Owls nest in old woodpecker cavities, (primarily those made by Pileated Woodpeckers or Northern Flickers) or in natural cavities. They will also take to nest boxes quite readily. Nest trees are often dead and nest heights average 4 to 6 metres (13-20 feet) above ground. Nesting occurs between March and July.
Clutch sizes range from 3 to 7 eggs (average 5-6) laid at periods of 1 to 3 days, but usually 2. Eggs average 30x25 mm (1.18x1"). The female does all incubation and the male brings food to her and defends the nesting area. The incubation period is 21 to 28 days. Young fledge at 4 to 5 weeks, and may leave the nest individually every 1 to 2 days, until they have all left. The young owls are cared for by the parents for some weeks after they leave the nest. Sexual maturity is reached at 9-10 months old.
A pair will raise a single brood; in years when food is abundant, they will nest slightly earlier in the season.
Mortality: Captive Owls have lived for 8 years, but mortality in the wild is likely relatively high. They compete with Boreal Owls, starlings, and squirrels for nest cavities, and are preyed upon by larger Owls, martens, Cooper's Hawks, and Northern Goshawks.
Habitat: Northern Saw-whet Owls inhabit coniferous and deciduous forests, with thickets of second-growth or shrubs. They occur mainly in forests with deciduous trees, where woodpeckers create cavities for nest sites. Breeding habitat is usually swampy or wet, rather than dry. Riparian habitat is often preferred.
Distribution: North America - Breeds from south-eastern Alaska, central British Columbia, including the Queen Charlotte Islands, central Alberta, central Saskatchewan, central Manitoba, central Ontario, southern Quebec, northern New Brunswick, Prince Edward Island, and Nova Scotia, south to the mountains of southern California to southern New Mexico, locally in western South Dakota and western Minnesota, northern Illinois, southern Michigan, central Ohio, West Virginia, western Maryland, and New York; also breeds locally in the mountains of eastern Tennessee and western North Carolina.
They Winter generally throughout much of the breeding range, but part of the population migrates south regularly to the central United States and irregularly to more southern areas along the Gulf coast and central Florida.
The Northern Saw-whet Owl is highly migratory in northern and eastern areas. Two major migration corridors in eastern North America are along the Atlantic coastline and down the Ohio River valley. Juveniles are more likely to migrate than adults and tend to move further south. Migration in the fall often occurs during the passage of a cold front and during westerly winds. Southern populations move down slope during winter rather than migrating south.
The Northern Saw-whet Owl is also found in Mexico.
Distribution of the Northern Saw-whet Owl Aegolius acadicus
Status: Not threatened or endangered. Locally frequent.
Original Description: Gmelin, Johann Friedrich. 1788. Systema Naturae, 1, Pt.1, p. 296.
A. a. acadicus,
A. a. brooksi,
A. a. brodkorbi
Campbell, Wayne. 1994. "Know Your Owls (CD-ROM)". Axia Wildlife
Page compiled by Deane Lewis. Page last updated 2013-05-29
OwlPages.com Owl Species ID: 230.020.000