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.
At a Glance
Habitat
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Food
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Nesting
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Behavior
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Conservation
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Forest
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Mammals
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Cavity
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Aerial Dive
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Least Concern
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Measurements
Both Sexes
Length
7.18.3
in
1821
cm
Wingspan
16.518.9
in
4248
cm
Weight
2.35.3
oz
65151
g
Relative Size
Slightly heavier (but more compact)
than a Hairy Woodpecker; smaller
than an Eastern Screech-Owl.
Other Names
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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
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Forest
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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
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Mammals
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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 Facts
Clutch Size
47 eggs
Number of Broods
1-2 broods
Egg Length
1.11.3
in
2.83.3
cm
Egg Width
0.91 in
2.42.6
cm
Incubation Period
2629 days
Nestling Period
2734 days
Egg Description
White and smooth.
Condition at Hatching
Semi-helpless
and covered with
white down, with eyes closed. |
Nesting
Nest Description
Saw-whets lay their eggs on debris at the bottom of the cavitysuch
as woodchips, twigs, moss, grass, hair, small mammal bones, or old
starling nestswithout adding new material to the nest. Nest
holes may be 844 feet off the ground, and they measure about
3 inches wide and 918 inches deep, with an entrance hole 23
inches across.
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.
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,
Coopers 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
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Least Concern
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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.
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