Bird of the Month: Northern Saw-whet Owl
Written by Andy McCormick
Andy McCormick, Volunteer and Former Board President of Eastside Audubon
One of our smallest owls, the Saw-whet Owl is nocturnal when it hunts small mammals and roosts during the day.
The Northern Saw-whet Owl is common across northern North America but is often overlooked. It is a solitary bird and stays quietly perched during the day, sometimes in the open. As they prowl a forested area, birders may unexpectedly come upon a Saw-whet Owl roosting on a low branch. They can be quite tame and indifferent to humans and may remain on the branch undisturbed.
The Saw-whet Owl is a tiny brown bird spotted with white on the back and streaked brown on the white chest. Nocturnal owls, such as the Saw-whet are adapted to live in extensive forests and a low light environment. The Saw-whet has large yellow or orange eyes. It has asymmetric ears positioned at different levels on its head which aid the owl in locating its prey with great accuracy as it receives sound at different times (Rasmussen et al). A white Y-shaped blaze marks the area between and above the eyes. A subspecies endemic to Haida Gwaii (A. a. brooksi) has rufous coloring which replaces the white (Aversa, et al).
Northern saw-whet owl
Scientific Name: Aegolius acadicus
Length: 8”
Wingspan: 17”
Weight: 2.8 oz (80 g)
AOU Alpha Code: NSWO
MORE OFTEN HEARD THAN SEEN
Researchers have identified eleven vocalizations for the Northern Saw-whet Owl (Rasmussen, et al). During the breeding season, as it marks its territory and attempts to attract a mate, the male Saw-whet calls out a continuous series of whistled toots beginning about two hours after dark and ending shortly before dawn. This call is similar to that of the Northern Pygmy-Owl but is given by the Saw-whet at a more rapid tempo.
In periods of distress, the male has an alternate call described as a slowly repeated whine. Some early writers compared this whine to the sound of a saw being sharpened over a whetstone, a common sound among European settlers to North America (Kaufman). Similarly, another writer reported in 1925 that the call resembled the sounds produced by filing a large mill-saw (Bent). This whine call is the one which led to this bird’s English name Saw-whet (Holloway). Bent also recounts another report documenting that this call is more commonly delivered in February and March.
DENIZEN OF THE FOREST
The Northern Saw-whet Owl is a bird which nests in a variety of forest habitats from deciduous to conifer. A major requirement for breeding success is the presence of an existing tree cavity, usually a nest hole excavated by a flicker or Pileated Woodpecker. Typically, 5-6 white eggs are deposited directly on any wood chips left by the flickers and sometimes a few feathers are present (Bent). Incubation is by the female only. She remains on the nest for the entire incubation period of more than three weeks. During this time the male brings food to the nest (Kaufman). After the eggs hatch, the male continues to provide food for the owlets through the fledgling stage until full independent is achieved about two months later. By this time the female will depart or may attempt a second brood with another mate.
The Saw-whet Owl shares the genus Aegolius, from the Greek aigolios, a type of owl, with the Boreal Owl (A. funereus), and two other owls: The Unspotted Saw-whet Owl (A. ridgwayi) of southern Mexico and Guatemala, and the Buff-fronted Owl (A. harrisii) of South America. The Bermuda Saw-whet Owl (A. gradyi) is extinct but is still listed in Birds of the World (Cornell Lab). The species epithet acadicus refers to Acadia (Nova Scotia) where the first science specimen was collected. Photos, videos, and vocalizations of the Saw-whet Owl can be found at The Macaulay Library.
STATUS AND DISTRIBUTION
The Northern Saw-whet Owl is widespread yet unobtrusive across the forested areas of Canada and the northern United States and at higher elevations through the western mountains into Mexico (Dunne). Many Saw-whet Owls are resident on the breeding grounds. However, many migrate and those that do move to the central and southern United States. Fall migration along the Pacific Northwest coast peaks during mid-October to mid-November. The population on Haida Gwaii does not migrate.
Although active at night, it is most often seen by humans during the day while roosting. It can be seen in the open often on the end of a branch low in a tree. It can also tarry during fall migration and has been known to roost on the railing of an apartment building balcony or on porch furniture in a suburban neighborhood.
Except for some local concern in North Carolina and South Dakota and for the subspecies on Haida Gwaii, the Northern Saw-whet Owl has not been listed as threatened or endangered. However, because it favors mature and old-growth forests for breeding, it is susceptible to loss of nesting habitat as older trees are felled. A possible remedy for the loss of natural tree cavities is the Saw-whet Owl’s acceptance of using nest boxes (Rasmussen et al).
Photo credit Mick Thompson. References available upon request from amccormick@eastsideaudubon.org.
References available upon request from amccormick@eastsideaudubon.org.