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    Northern Saw-whet Owl Life History

    Habitat

    Habitat ForestsNorthern 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.Back to top

    Food

    Food MammalsNorthern 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.Back to top

    Nesting

    Nest Placement

    Nest CavityFemales 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.

    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.

    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:0.9-1.0 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.
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    Behavior

    Behavior Aerial Dive (ground/talons)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.Back to top

    Conservation

    Conservation Low ConcernNorthern 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 a global breeding population of 2 million, with 71% spending some part of the year in the U.S., 46% in Canada and 4% in Mexico. They rate a 8 out of 20 on the Continental Concern Score and only the regional, Southern Appalachian Northern Saw-whet Owl population is listed on the 2014 State of the Birds Watch List, which lists bird species that are at risk of becoming threatened or endangered without conservation action. 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.Back to top

    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.

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    Credits

    Ehrlich, P. R., D. S. Dobkin and D. Wheye. 1988. The birder's handbook. A Field Guide to the natural history of North American birds, including all species that regularly breed north of Mexico. New York: Simon and Schuster, Inc.

    Lutmerding, J. A. and A. S. Love. Longevity records of North American birds. Version 2015.2. Patuxent Wildlife Research Center, Bird Banding Laboratory 2015.

    North American Bird Conservation Initiative. 2014. The State of the Birds 2014 Report. US Department of Interior, Washington, DC, USA.

    Partners in Flight. 2017. Avian Conservation Assessment Database. 2017.

    Rasmussen, Justin Lee, Spencer G. Sealy and Richard J. Cannings. 2008. Northern Saw-whet Owl (Aegolius acadicus), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

    Sibley, David Allen. 2014. The Sibley guide to birds, second edition. Alfred A Knopf, New York.

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