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Northern Saw-whet Owl

Aegolius acadicus ORDER: STRIGIFORMES FAMILY: STRIGIDAE

IUCN Conservation Status: Least Concern

A tiny owl with a catlike face, oversized head, and bright yellow eyes, the Northern Saw-whet Owl is practically bursting with attitude. Where mice and other small mammals are concerned this fierce, silent owl is anything but cute. One of the most common owls in forests across northern North America (and across the U.S. in winter), saw-whets are highly nocturnal and seldom seen. Their high-pitched too-too-too call is a common evening sound in evergreen mountain forests from January through May.

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At a GlanceHelp

Measurements
Both Sexes
Length
7.1–8.3 in
18–21 cm
Wingspan
16.5–18.9 in
42–48 cm
Weight
2.3–5.3 oz
65–151 g
Relative Size
Slightly heavier (but more compact) than a Hairy Woodpecker; smaller than an Eastern Screech-Owl.
Other Names
  • Petite nyctale (French)
  • Lechucita cabezona, Tecolotito cabezon (Spanish)

Cool Facts

  • The Northern Saw-whet Owl may have been named for giving a call that sounds like a saw being sharpened on a whetting stone, but there is no consensus as to which of its several calls gave rise to the name.
  • The main prey items of the Northern Saw-whet Owl are mice, and especially deer mice of the genus Peromyscus. Saw-whets usually eat adult mice in pieces, over the course of two meals.
  • The female Northern Saw-whet Owl does all of the incubation and brooding, while the male does the hunting. When the youngest nestling is about 18 days old, the female leaves the nest to roost elsewhere. The male continues bringing food, which the older nestlings may help feed to their younger siblings.
  • The female saw-whet keeps the nest very clean, but a mess starts to accumulate when she leaves. By the time the young owls leave the nest, 10 days to 2 weeks later, the nest cavity has a thick layer of feces, pellets, and rotting prey parts.
  • Migration in saw-whets has historically been poorly understood, because of their nocturnal, reclusive behavior. In the 1990s researchers began Project Owlnet, a collaboration that now consists of more than 100 owl migration banding sites. Researchers use the too-too-too call to lure owls in to mist nets, and band thousands of saw-whets every fall.
  • Migrating Northern Saw-whet Owls can cross the Great Lakes or other large bodies of water. In October of 1999, one landed on a fishing vessel 70 miles from shore in the Atlantic Ocean near Montauk, New York.
  • The oldest Northern Saw-whet Owl on record was at least 9 years, 5 months old when it was captured and released by a Minnesota bird bander in 2007. It was originally banded in Ontario in 1999.

Habitat


Forest

Northern Saw-whet Owls breed in forests across southern Canada and the northern and western United States, extending through central Mexico. They seem to prefer mature forest with an open understory for foraging, deciduous trees for nesting, dense conifers for roosting, and riverside habitat nearby. But they nest in a wide range of wooded habitats, including coniferous swamps, disturbed deciduous woods, savannahs, riverside forest, and shrub-steppe habitat. They also nest in boxes placed in coastal scrub, sand dune meadows, and poplar plantations. Saw-whets winter in dense forest throughout the breeding range and across most of the United States, excluding the southernmost edges.

Food


Mammals

Northern Saw-whet Owls eat mostly small mammals, hunting them at night from a low perch along the forest edge. The most common prey are deer mice and white-footed mice, but may include shrews, house mice, harvest mice, pocket mice, jumping mice, montane voles, red-backed voles, meadow voles, heather voles, red tree voles, shrew-moles, bats, and juveniles of larger mammals like pocket gophers, chipmunks, and squirrels. During migration they supplement their diet with birds, such as titmice, chickadees, kinglets, juncos, waxwings, sparrows, thrushes, wrens, warblers, robins, and even other small owl species. They may eat beetles, grasshoppers, moths, and bugs. Saw-whets that live along the coasts may eat intertidal invertebrates such as amphipods and isopods. Males provide nearly all of the food while females are incubating and brooding the young.

Nesting

Nesting Facts
Clutch Size
4–7 eggs
Number of Broods
1-2 broods
Egg Length
1.1–1.3 in
2.8–3.3 cm
Egg Width
0.9–1 in
2.4–2.6 cm
Incubation Period
26–29 days
Nestling Period
27–34 days
Egg Description
White and smooth.
Condition at Hatching
Semi-helpless and covered with white down, with eyes closed.
Nest Description

Saw-whets lay their eggs on debris at the bottom of the cavity—such as woodchips, twigs, moss, grass, hair, small mammal bones, or old starling nests—without adding new material to the nest. Nest holes may be 8–44 feet off the ground, and they measure about 3 inches wide and 9–18 inches deep, with an entrance hole 2–3 inches across.

Nest Placement

Cavity

Females probably choose the nest site, although males sometimes participate by perching in potential sites while giving their too-too-too call. They nest in previously excavated holes (usually those of Northern Flickers or Pileated Woodpeckers) in dead snags. They also use nest boxes.

Behavior


Aerial Dive

Although saw-whets are usually monogamous, when prey is abundant each male may have more than one mate. Males start giving their too-too-too call as early as late January, before females arrive, and continue until May. When a female hears a male calling she responds with a high-pitched tssst call or a series of whistles. The male circles her about 20 times in flight before landing beside her and presenting a prey item. Some year-round resident males or pairs probably maintain territories throughout the year, but each year they pair up with new mates. Saw-whets are preyed on by larger raptors, including Eastern Screech-Owls, Spotted Owls, Great Horned Owls, Cooper’s Hawks, Broad-winged Hawks, and Peregrine Falcons. They roost during the day in thick conifers at an average of 11 feet above the ground, often hidden by foliage near the outer edge of a branch. They are occasionally discovered by mixed-species flocks of songbirds, which mob the predator in an effort to drive it away. Tuning in to all that commotion is one of the best ways for bird watchers to find these well-hidden owls.

Conservation

status via IUCN

Least Concern

Northern Saw-whet Owls are common and widespread, but their secretive lifestyle makes population trends difficult to identify with standardized surveys such as the North American Breeding Bird Survey or the Christmas Bird Count. Partners in Flight estimates the global breeding population at 2 million, with 71 percent spending some part of the year in the U.S., 46 percent in Canada and 4 percent in Mexico. They rate a 9 out of 20 on the Continental Concern Score and are not on the 2012 Watch List. Overall, their population has probably declined in past decades due to habitat loss. North Carolina and South Dakota have listed them as a species of special concern, and a subspecies native to the Queen Charlotte Islands of British Columbia is threatened. Although saw-whets breed in many forest types, they favor mature stands which may come under pressure for logging or development. People can maintain the suitability of forest habitat by allowing dead trees to remain standing to provide nest cavities. Saw-whets take readily to nest boxes, which can also be used to mitigate the loss of natural sites. Large-scale habitat shifts caused by climate change may affect the southern range limit of this species in the future.

Credits

Range Map Help

Northern Saw-whet Owl Range Map
View dynamic map of eBird sightings

Migration

Resident to long-distance migrant. Many individuals migrate south or to lower elevations for the winter, while others stay in one place year-round. About once every 4 years they irrupt, heading south in much higher numbers than usual. They migrate at night, using several known migration routes across the continent, and can cross large expanses of water.

Backyard Tips

If you live on an extensively wooded lot within the Northern Saw-whet Owl’s breeding range, consider putting up a nest box to attract a breeding pair. Make sure you put it up well before breeding season. Attach a guard to keep predators from raiding eggs and young. Find out more about nest boxes on our Attract Birds pages. You'll find plans for building a nest box of the appropriate size on our All About Birdhouses site.

Find This Bird

It’s hard to see a Northern Saw-whet Owl, but you may hear them on quiet nights from January to May in forests of northern and western North America. Listen for a sharp, high, repeated too-too-too call. During the day these small, hard-to-find owls roost silently in dense conifers. Your best chance of seeing them is to pay attention to small songbirds—if they discover a roosting saw-whet, they’re likely to kick up a racket, calling and flying at the owl until it moves one.