The Northern Saw-whet Owl is one of the smallest and most common owls in forested habitats in southern Canada and the United States. Much remains to be learned about its populations, distribution, movements, and behaviour and breeding territory. It’s year round and breeding range spans much of North America and central Mexico.
Adult Male (spring/summer)
The facial disk is pale buff edged with dark brown around the outer edges, fading to white above, below and between the eyes. The eyes are yellow-golden and the bill is black. There are no ear tufts. The crown is dark brown with white streaks and the nape is dark brown with white spots. The back, scapulars, rump and uppertail coverts are dark brown with sparse white spots. Tail is short, dark brown with white barring and tips. Wings are dark brown with white spots. The belly and flanks are white with broad reddish brown streaks. Undertail coverts are white. The white to buff legs and feet are densely feathered.
Adult Female (spring/summer)
Similar to adult male.
Juvenile
Very compact and round. Reddish brown above and the facial disk has a contrasting white triangle on forehead. Underparts are tawny-rust.
General:
Very small owl with large, rounded head. Length: 18-21cm. Wing: 42-48cm. Weight: 65-151 grams.
Behaviour:
The Northern Saw-whet Owl is almost entirely nocturnal, occasionally hunting during daylight hours in winter. It hunts mostly by waiting on low perches and then swooping down on prey, finding it by sight and sound. Roost sites are typically in large conifers, near the end of a low branch sheltered by foliage. Tree cavities are seldom used as roost sites. It feeds mostly on mice, especially deer mice. It also eats voles, shrews, young squirrels, small birds and large insects.
Habitat:
Breeds in a variety of forested woodlands within its range but prefers old growth coniferous forests. Winter habitat varies widely including rural and semi-rural habitats provided they offer dense cover, especially groves of conifers. Nonbreeding birds typically roost in the same site for weeks or months, while breeding males usually use a different roost each day.
Information:
Saw-whet Owls are secretive, nocturnal and have irregular movement patterns and are subsequently difficult to study. Some Saw-whets remain within the breeding range year round. Many Saw-whets move southward in winter, with large concentrations in spring and fall around the Great Lakes. During breeding season males give a rhythmic tooting song that may go on for hours with scarcely a break. The bird was named for this song, which reminded settlers of the sound of a whetstone sharpening a saw. Nest sites are in tree cavities. They also use nest boxes. Eggs are laid on debris at the bottom of the cavity-such as woodchips, twigs, moss, grass and hair. Clutch size is 4-7 white eggs.
Similar species:
Northern Pygmy Owl, Flammulated Owl
Conservation Status:
Listed as Least Concern. They are common and widespread, but their secretive lifestyle makes population trends difficult to ascertain.
Capture Rates:
The Northern Saw-whet Owl is a small nocturnal owl found in portions of southern Canada and northern USA. The species is partly migratory throughout its range, with large numbers of owls captured and banded at monitoring stations in British Columbia each fall, including hundreds captured at the Rocky Point Bird Observatory (RPBO) on the southern tip of Vancouver Island which suggests that significant numbers of owls migrate through southern Vancouver Island each fall. The numbers captured at the VARC banding station at Colony Farm Regional Park in Port Coquitlam are much lower and this raises questions about the migratory routes of these owls. At present, the migratory routes and destination for these birds remain poorly understood because so few birds are subsequently recaptured after traditional banding activities.
Molt Summary:
PF: HY partial (Jul-Dec); PB: AHY incomplete-complete (May-Nov); PA absent. Molts occur primarily on the summer grounds.
Preformative molt includes all body feathers but no wing coverts. The 2nd PB usually includes the outermost 1-7 pp and the innermost 3-9 (of 13) ss. The 3rd PB usually includes the innermost 2-4 pp (among p1-p4), usually leaving 2-4 central pp (among p3-p7) as juvenal feathers, and the outermost 2-6 ss (among s1-s6), often leaving 1-6 central ss (among s4-s9) as juvenal feathers. Subsequent PBs are irregular, resulting in mixed wing feather generations.
Replacement of the rects typically is complete during adult PBs.
Juveniles have loosely textured or downy plumage, with the upperparts and head uniformly dark reddish brown or sotty in coloration (tips of down can remain on HYs after fledging). Juv M=F.
Ageing and sexing Northern Saw-whet Owls is relatively easy. Hatch year (HY) birds do not replace remiges (primaries and secondaries) in their preformative molt and therefore, as in the bird above, all primaries and secondaries are a uniform shade of brown.
This is even easier to see under Ultraviolet light, as the porphyrin in the feathers glows pink across the entire underside of the wing.
This HY in October is showing retained juvenal flight feathers, the primaries and secondaries uniform in wear and showing no contrasts. The primaries often show narrow, white edges (red arrow).
A second year (SY) bird replaces the outer primaries and inner secondaries after its first breeding season. These replaced feathers contrast visibly with the retained inner primaries and outer secondaries and again, the new feathers glow pink while the older feathers are washed out and bluish under ultraviolet light.
This SY in October has replaced the outer two primaries and innermost visible secondaries. Compare the rachis colour of the replaced (dark chocolate) and retained (milk chocolate) feathers.
Third year (TY) birds like the bird below show an increasingly fragmented pattern with 3 distinct generations of feathers.
After second year (ASY) birds show a pattern of mixed new, one-year old and two-year old feathers.
And after third year (ATY) and fourth year (4Y) birds show complex patterns in which 4 generations of feathers can possibly be identified.
Sexing
As female Northern Saw-whet owls are generally heavier and have longer wings than males, sexing birds is also relatively easy using a combination of body mass and wing chord to determine sex.